Prostate cancer is a form of cancer that develops in the prostate, a gland in the male reproductive system. Most prostate cancers are slow growing;[1] however, there are cases of aggressive prostate cancers.[2] The cancer cells may metastasize (spread) from the prostate to other parts of the body, particularly the bones and lymph nodes. Prostate cancer may cause
pain, difficulty in urinating, problems during sexual intercourse, or erectile dysfunction. Other symptoms can potentially develop during later stages of the disease.
Rates of detection of prostate cancers vary widely across the world, with South and East Asia detecting less frequently than in Europe, and especially the United States.[3] Prostate cancer tends to develop in men over the age of fifty.[4] Globally it is the sixth leading cause of cancer-related death in men[5] (in the United States it is the second).[4] Prostate cancer is most common in the developed world with increasing rates in the developing world.[5] However, many men with prostate cancer never have symptoms, undergo no therapy, and eventually die of other unrelated causes. Many factors, including genetics and diet, have been implicated in the development of prostate cancer.
The presence of prostate cancer may be indicated by symptoms, physical examination, prostate-specific antigen (PSA), or biopsy. Prostate-specific antigen testing increases cancer detection but does not decrease mortality.[6] The United States Preventive Services Task Force in 2012 recommended against screening for prostate cancer using the PSA testing, due to the risk of over-diagnosis and over-treatment with most prostate cancer remaining asymptomatic.[7] The USPSTF concludes that the potential benefit of testing does not outweigh the expected harms.[7]
Management strategies for prostate cancer should be guided by the severity of the disease. Many low-risk tumors can be safely followed with active surveillance. Curative treatment generally involves surgery, various forms of radiation therapy, or, less commonly, cryosurgery; hormonal therapy and chemotherapy are generally reserved for cases of advanced disease (although hormonal therapy may be given with radiation in some cases). Several studies suggest that masturbation reduces the risk of prostate cancer.[8][9][10]
The age and underlying health of the man, the extent of metastasis, appearance under the microscope and response of the cancer to initial treatment are important in determining the outcome of the disease. The decision whether or not to treat localized prostate cancer (a tumor that is contained within the prostate) with curative intent is a patient trade-off between the expected beneficial and harmful effects in terms of patient survival and quality of life.
Prostate cancer is associated with urinary dysfunction as the prostate gland surrounds the prostatic urethra. Changes within the gland, therefore, directly affect urinary function. Because the vas deferens deposits seminal fluid into the prostatic urethra, and secretions from the prostate gland itself are included in semen content, prostate cancer may also cause problems with sexual function and performance, such as difficulty achieving erection or painful ejaculation.[11]
Advanced prostate cancer can spread to other parts of the body, possibly causing additional symptoms. The most common symptom is bone pain, often in the vertebrae (bones of the spine), pelvis, or ribs. Spread of cancer into other bones such as the femur is usually to the proximal part of the bone. Prostate cancer in the spine can also compress the spinal cord, causing leg weakness and urinary and fecal incontinence.[12]
No single gene is responsible for prostate cancer; many different genes have been implicated. Mutations in BRCA1 and BRCA2, important risk factors for ovarian cancer and breast cancer in women, have also been implicated in prostate cancer.[25] Other linked genes include the Hereditary Prostate cancer gene 1 (HPC1), the androgen receptor, and the vitamin D receptor.[22] TMPRSS2-ETS gene family fusion, specifically TMPRSS2-ERG or TMPRSS2-ETV1/4 promotes cancer cell growth.[26]
Loss of cancer suppressor genes, early in the prostatic carcinogenesis, have been localized to chromosomes 8p, 10q, 13q,and 16q. P53 mutations in the primary prostate cancer are relatively low and are more frequently seen in metastatic settings, hence, p53 mutations are late event in pathology of prostate cancer. Other tumor suppressor genes that are thought to play a role in prostate cancer include PTEN (gene) and KAI1. "Up to 70 percent of men with prostate cancer have lost one copy of the PTEN gene at the time of diagnosis"[27] Relative frequency of loss of E-cadherin and CD44 has also been observed.
Two large genome-wide association studies linking single nucleotide polymorphisms (SNPs) to prostate cancer were published in 2008.[28][29] These studies identified several SNPs which substantially affect the risk of prostate cancer. For example, individuals with TT allele pair at SNP rs10993994 were reported to be at 1.6 times higher risk of prostate cancer than those with the CC allele pair. This SNP explains part of the increased prostate cancer risk of African American men as compared to American men of European descent, since the C allele is much more prevalent in the latter; this SNP is located in the promoter region of the MSMB gene, thus affects the amount of MSMB protein synthesized and secreted by epithelial cells of the prostate.[30]
Lower blood levels of vitamin D may increase the risk of developing prostate cancer.[35]
Taking multivitamins more than seven times a week may increase the risk of developing the disease.[36][37][non-primary source needed]
A 2009 study on folic acid supplements showed an association with an increased risk of developing prostate cancer.[38][non-primary source needed]
Infection or inflammation of the prostate (prostatitis) may increase the chance for prostate cancer while another study shows infection may help prevent prostate cancer by increasing blood to the area. In particular, infection with the sexually transmitted infections chlamydia, gonorrhea, or syphilis seems to increase risk.[41] Finally, obesity[42] and elevated blood levels of testosterone[43] may increase the risk for prostate cancer. There is an association between vasectomy and prostate cancer however more research is needed to determine if this is a causative relationship.[44]
Research released in May 2007, found that US war veterans who had been exposed to Agent Orange had a 48% increased risk of prostate cancer recurrence following surgery.[45]
The prostate is a part of the male reproductive system that helps make and store seminal fluid. In adult men, a typical prostate is about three centimeters long and weighs about twenty grams.[60] It is located in the pelvis, under the urinary bladder and in front of the rectum. The prostate surrounds part of the urethra, the tube that carries urine from the bladder during urination and semen during ejaculation.[61] Because of its location, prostate diseases often affect urination, ejaculation, and rarely defecation. The prostate contains many small glands which make about twenty percent of the fluid constituting semen.[62] In prostate cancer, the cells of these prostate glands mutate into cancer cells. The prostate glands require male hormones, known as androgens, to work properly. Androgens include testosterone, which is made in the testes; dehydroepiandrosterone, made in the adrenal glands; and dihydrotestosterone, which is converted from testosterone within the prostate itself. Androgens are also responsible for secondary sex characteristics such as facial hair and increased muscle mass.
When normal cells are damaged beyond repair, they are eliminated by apoptosis. Cancer cells avoid apoptosis and continue to multiply in an unregulated manner.
Prostate cancer is classified as an adenocarcinoma,
or glandular cancer, that begins when normal semen-secreting prostate
gland cells mutate into cancer cells. The region of prostate gland where
the adenocarcinoma is most common is the peripheral zone. Initially,
small clumps of cancer cells remain confined to otherwise normal
prostate glands, a condition known as carcinoma in situ or prostatic intraepithelial neoplasia
(PIN). Although there is no proof that PIN is a cancer precursor, it is
closely associated with cancer. Over time, these cancer cells begin to
multiply and spread to the surrounding prostate tissue (the stroma) forming a tumor. Eventually, the tumor may grow large enough to invade nearby organs such as the seminal vesicles or the rectum, or the tumor cells may develop the ability to travel in the bloodstream and lymphatic system. Prostate cancer is considered a malignant tumor because it is a mass of cells that can invade other parts of the body. This invasion of other organs is called metastasis. Prostate cancer most commonly metastasizes to the bones, lymph nodes, and may invade rectum, bladder and lower ureters after local progression. The route of metastasis to bone is thought to be venous as the prostatic venous plexus draining the prostate connects with the vertebral veins.[63]
The prostate is a zinc accumulating, citrate producing organ. The protein ZIP1 is responsible for the active transport of zinc into prostate cells. One of zinc's important roles is to change the metabolism of the cell in order to produce citrate, an important component of semen. The process of zinc accumulation, alteration of metabolism, and citrate production is energy inefficient, and prostate cells sacrifice enormous amounts of energy (ATP) in order to accomplish this task. Prostate cancer cells are generally devoid of zinc. This allows prostate cancer cells to save energy not making citrate, and utilize the new abundance of energy to grow and spread. The absence of zinc is thought to occur via a silencing of the gene that produces the transporter protein ZIP1. ZIP1 is now called a tumor suppressor gene product for the gene SLC39A1. The cause of the epigenetic silencing is unknown. Strategies which transport zinc into transformed prostate cells effectively eliminate these cells in animals. Zinc inhibits NF-ÎşB pathways, is anti-proliferative, and induces apoptosis in abnormal cells. Unfortunately, oral ingestion of zinc is ineffective since high concentrations of zinc into prostate cells is not possible without the active transporter, ZIP1.[64]
RUNX2 is a transcription factor that prevents cancer cells from undergoing apoptosis thereby contributing to the development of prostate cancer.[65]
The PI3k/Akt signaling cascade works with the transforming growth factor beta/SMAD signaling cascade to ensure prostate cancer cell survival and protection against apoptosis.[66] X-linked inhibitor of apoptosis (XIAP) is hypothesized to promote prostate cancer cell survival and growth and is a target of research because if this inhibitor can be shut down then the apoptosis cascade can carry on its function in preventing cancer cell proliferation.[67] Macrophage inhibitory cytokine-1 (MIC-1) stimulates the focal adhesion kinase (FAK) signaling pathway which leads to prostate cancer cell growth and survival.[68]
The androgen receptor helps prostate cancer cells to survive and is a target for many anti cancer research studies; so far, inhibiting the androgen receptor has only proven to be effective in mouse studies.[69] Prostate specific membrane antigen (PSMA) stimulates the development of prostate cancer by increasing folate levels for the cancer cells to use to survive and grow; PSMA increases available folates for use by hydrolyzing glutamated folates.[70]
The only test that can fully confirm the diagnosis of prostate cancer is a biopsy, the removal of small pieces of the prostate for microscopic examination. However, prior to a biopsy, less invasive testing can be conducted.
According to Professor Hardev Pandha, The Prostate Project Chair of Urological Oncology at the University of Surrey's Postgraduate Medical School, a non-invasive test looking for the presence of the protein Engrailed-2 (EN2) in the urine to be more reliable and accurate than existing tests.
"In this study, we showed that the new test was twice as good at finding prostate cancer as the standard PSA test. Only rarely did we find EN2 in the urine of men who were cancer free, so if we find EN2 we can be reasonably sure that a man has prostate cancer. EN2 was not detected in men with non-cancer disorders of the prostate such as prostatitis or benign enlargement. These conditions often cause a high PSA result, causing considerable stress for the patient and sometimes also unnecessary further tests such as prostate biopsies." [72]
There are also several other tests that can be used to gather more information about the prostate and the urinary tract. Digital rectal examination (DRE) may allow a doctor to detect prostate abnormalities. Cystoscopy shows the urinary tract from inside the bladder, using a thin, flexible camera tube inserted down the urethra. Transrectal ultrasonography creates a picture of the prostate using sound waves from a probe in the rectum.
Micrograph showing a prostate cancer (conventional adenocarcinoma) with perineural invasion. H&E stain.
If cancer is suspected, a biopsy is offered expediently. During a biopsy a urologist or radiologist
obtains tissue samples from the prostate via the rectum. A biopsy gun
inserts and removes special hollow-core needles (usually three to six on
each side of the prostate) in less than a second. Prostate biopsies are
routinely done on an outpatient basis and rarely require
hospitalization. Fifty-five percent of men report discomfort during
prostate biopsy.[77]
Small cell carcinoma is a very rare (1%[79]) type of prostate cancer that cannot be diagnosed using the PSA.[79][80] As of 2009 researchers are trying to determine the best way to screen for this type of prostate cancer because it is a relatively unknown and rare type of prostate cancer but very serious and quick to spread to other parts of the body.[80] Possible methods include chromatographic separation methods by mass spectrometry, or protein capturing by immunoassays or immunized antibodies. The test method will involve quantifying the amount of the biomarker PCI, with reference to the Gleason Score. Not only is this test quick, it is also sensitive. It can detect patients in the diagnostic grey zone, particularly those with a serum free to total Prostate Specific Antigen ratio of 10-20%.[81]
The oncoprotein BCL-2, has been associated with the development of androgen-independent prostate cancer due to its high levels of expression in androgen-independent tumours in advanced stages of the pathology. The upregulation of BCL-2 after androgen ablation in prostate carcinoma cell lines and in a castrated-male rat model further established a connection between BCL-2 expression and prostate cancer progression.[82]
The expression of Ki-67 by immunohistochemistry may be a significant predictor of patient outcome for men with prostate cancer.[83]
ERK5 is a protein that may be used as a marker. ERK5 is present in abnormally high levels of prostate cancer, including invasive cancer which has spread to other parts of the body. It is also present in relapsed cancer following previous hormone therapy. Research shows that reducing the amount of ERK5 found in cancerous cells reduces their invasiveness.[84]
The most important distinction made by any staging system is whether or not the cancer is still confined to the prostate. In the TNM system, clinical T1 and T2 cancers are found only in the prostate, while T3 and T4 cancers have spread elsewhere. Several tests can be used to look for evidence of spread. Medical specialty professional organizations recommend against the use of PET scans, CT scans, or bone scans when a physician stages early prostate cancer with low risk for metastasis.[86][87] Those tests would be appropriate in such cases as when a CT scan evaluates spread within the pelvis, a bone scan look for spread to the bones, and endorectal coil magnetic resonance imaging to closely evaluate the prostatic capsule and the seminal vesicles. Bone scans should reveal osteoblastic appearance due to increased bone density in the areas of bone metastasis—opposite to what is found in many other cancers that metastasize.
After a prostate biopsy, a pathologist looks at the samples under a microscope. If cancer is present, the pathologist reports the grade of the tumor. The grade tells how much the tumor tissue differs from normal prostate tissue and suggests how fast the tumor is likely to grow. The Gleason system is used to grade prostate tumors from 2 to 10, where a Gleason score of 10 indicates the most abnormalities. The pathologist assigns a number from 1 to 5 for the most common pattern observed under the microscope, then does the same for the second-most-common pattern. The sum of these two numbers is the Gleason score. The Whitmore-Jewett stage is another method sometimes used.
While the available evidence is weak,[97] tentative results suggest that frequent ejaculation may decrease the risk of prostate cancer.[98] Men who get regular exercise may have a slightly lower risk, especially vigorous activity and the risk of advanced prostate cancer.[96]
The United States Preventive Services Task Force (USPSTF) recommends against the PSA test for prostate cancer screening in healthy men regardless of age.[101] They conclude that the potential benefit of testing does not outweigh the expected harms.[7][102] The Centers for Disease Control and Prevention shared that conclusion.[103] The American Society of Clinical Oncology recommends screening be discouraged in those who are expected to live less than ten years, while in those with a life expectancy of greater than ten years a decision should be made by the person in question based on the potential risks and benefits.[104]
Which option is best depends on the stage of the disease, the Gleason score, and the PSA level. Other important factors are age, general health, and a person's views about potential treatments and their possible side effects. Because all treatments can have significant side effects, such as erectile dysfunction and urinary incontinence, treatment discussions often focus on balancing the goals of therapy with the risks of lifestyle alterations. A combination of the treatment options is often recommended for managing prostate cancer.[106][107][108]
Guidelines for treatment for specific clinical situations requires a good estimation of a person's long-term life expectancy.[109] People can also use an 18-item questionnaire to learn whether they have good knowledge and understanding about their treatment options before they choose. Most of those who are newly diagnosed and made a treatment choice can not correctly answer over half of the questions.[109]
If radiation therapy is done first, and fails, then radical prostatectomy is very technically challenging surgery and may not be feasible. On the other hand, radiation therapy done after surgical failure may have many complications.[110]
In localized disease it is unknown if radical prostatectomy is better or worse than watchful waiting.[111]
Active surveillance involves monitoring the tumor for signs of growth or the appearance of symptoms. The monitoring process may involve serial PSA, physical examination of the prostate, and/or repeated biopsies. The goal of surveillance is to avoid overtreatment and the sometimes serious, permanent side effects of treatment for a slow-growing or self-limited tumor that would never cause any problems for the patient. This approach is not used for aggressive cancers, but it may cause anxiety for patients who wrongly believe that all cancer is deadly or themselves to have a life-threatening cancer.
For 50% to 75% of people with prostate cancer it will cause no harm before a person dies.[112]
Although the widespread use of prostate specific antigen (PSA) screening in the USA has resulted in diagnosis at earlier age and cancer stage, the vast majority of cases are still diagnosed in men older than 65 years, and approximately 25% of cases are diagnosed in men older than 75 years.[115] Though US National Comprehensive Cancer Network guidelines[116] recommend using life expectancy greater than or less than 10 years to help make treatment decisions, in practice, many elderly patients are not offered curative treatment options such as radical prostatectomy or radiation therapy and are instead treated with hormonal therapy or watchful waiting. This pattern can be attributed to factors such as medical co-morbidity and patient preferences is regard to quality of life in addition to prostate cancer specific risk factors such as pretreatment PSA, Gleason score and clinical stage. As the average life expectancy increases due to advances in treatment of cardiovascular, pulmonary and other chronic disease, it is likely that more elderly patients will be living long enough to suffer the consequences of their prostate cancer. Therefore, there is currently much interest in the role of aggressive prostate cancer treatment modalities such as with surgery or radiation in the elderly population who have localized disease. The results of one randomized controlled trial published by the Scandinavian Prostate Cancer Group 4 [117] evaluated cancer-specific mortality in patients treated with RP compared with watchful waiting. The patients receiving radical prostatectomy had a relative risk reduction of 30.7% [95% confidence interval 2.5%-50.7%], but an absolute risk reduction of 6% [95% confidence interval 0.5%-11.5%]. The number needed to treat was calculated to be 16. This means that, over the median follow up period of approximately 10 years, 16 patients with localized prostate cancer would need to receive radical prostatectomy rather than watchful waiting in order to prevent one death due to prostate cancer. Further subset analysis revealed that this benefit did not apply to all ages equally. In men younger than 65 years, patients randomized to receive radical prostatectomy actually had a 10-18% absolute risk reduction in cancer-specific mortality compared to those randomized to watchful waiting. However, in men older than 65, there was no statistically significant risk reduction even when adjusted for PSA level, Gleason score and tumor stage. Randomized, controlled trials comparing radical prostatectomy, radiation therapy, hormonal therapy and watchful waiting would provide the best evidence for how to best treat elderly patients.
If the cancer has spread beyond the prostate, treatment options significantly change, so most doctors that treat prostate cancer use a variety of nomograms to predict the probability of spread. Treatment by watchful waiting/active surveillance, external beam radiation therapy, brachytherapy, cryosurgery, HIFU, and surgery are, in general, offered to men whose cancer remains within the prostate. Hormonal therapy and chemotherapy are often reserved for disease that has spread beyond the prostate. However, there are exceptions: radiation therapy may be used for some advanced tumors, and hormonal therapy is used for some early stage tumors. Cryotherapy (the process of freezing the tumor), hormonal therapy, and chemotherapy may also be offered if initial treatment fails and the cancer progresses.
Sipuleucel-T has been found result in a benefit ( a four month increase in survival ) for men with metastatic prostate cancer.[118]
The cancer chemotherapic docetaxel has been used as treatment for CRPC with a median survival benefit of 2 to 3 months.[120][121] A second-line chemotherapy treatment is cabazitaxel.[122]
Off-label use of the oral drug ketoconazole is sometimes used as a way to further manipulate hormones with a therapeutic effect in CRPC. However, many side effects are possible with this drug and abiraterone is likely to supplant usage since it has a similar mechanism of action with less toxic side effects.
A combination of bevacizumab (Avastin), docetaxel, thalidomide and prednisone appears effective in the treatment of CRPC.[123]
The immunotherapy treatment with sipuleucel-T is also effective in the treatment of CRPC with a median survival benefit of 4.1 months.[124]
The second line hormonal therapy abiraterone (Zytiga) increased overall survival increased by 4.6 months when compared to placebo. Abiraterone acetate in combination with prednisone to treat people with late-stage (metastatic) castration-resistant prostate cancer who have received prior docetaxel (chemotherapy).[125] Enzalutamide is another second line hormonal agent which has demonstrated a 5 month survival advantage over placebo. Both abiraterone and enzalutamide are currently being tested in clinical trials with CRPC patients who have not previously received chemotherapy.
Only a subset of a patient respond to androgen signaling blocking drugs and certain cells with characteristics resembling stem cells remain unaffected.[126][127] Therefore, the desire to improve outcome of CRPC patients has resulted into the claims of increasing doses further or combination therapy with synergistic androgen signaling blocking agents.[128] But even these combination will not affect stem -like cells that do not exhibit androgen signaling. It is possible that for further advances, a combination of androgen signaling blocking agent with stem-like cell directed differentiation therapy drug would prove ideal.[129]
In patients who undergo treatment, the most important clinical prognostic indicators of disease outcome are stage, pre-therapy PSA level, and Gleason score. In general, the higher the grade and the stage, the poorer the prognosis. Nomograms can be used to calculate the estimated risk of the individual patient. The predictions are based on the experience of large groups of patients suffering from cancers at various stages.[135]
In 1941, Charles Huggins reported that androgen ablation therapy causes regression of primary and metastatic androgen-dependent prostate cancer.[136] He was awarded the 1966 Nobel Prize for Physiology or Medicine for this discovery. Androgen ablation therapy causes remission in 80-90% of patients undergoing therapy, resulting in a median progression-free survival of 12 to 33 months. After remission, an androgen-independent phenotype typically emerges, wherein the median overall survival is 23–37 months from the time of initiation of androgen ablation therapy.[137] The actual mechanism contributes to the progression of prostate cancer is not clear and may vary between individual patient. A few possible mechanisms have been proposed.[138]
Age-standardized death from prostate cancer per 100,000 inhabitants in 2004.[144]
As of 2011, prostate cancer is the second most frequently diagnosed
cancer and the sixth leading cause of cancer death in males worldwide.[145]
Rates of prostate cancer vary widely across the world. Although the
rates vary widely between countries, it is least common in South and
East Asia, more common in Europe, and most common in the United States.[3] According to the American Cancer Society, prostate cancer is least common among Asian men and most common among black men, with figures for white men in between.[146][147]
The average annual incidence rate of prostate cancer between 1988 and
1992 among Chinese men in the United States was 15 times higher than
that of their counterparts living in Shanghai and Tianjin.[146][147][148] However, these high rates may be affected by increasing rates of detection.[149] Many suggest that prostate cancer may be under reported, yet BPH incidence in China and Japan is similar to rates in Western countries.,[150][151]
Prostate cancer develops primarily in men over fifty. It is the most common type of cancer in men in the United States, with 186,000 new cases in 2008 and 28,600 deaths.[152] It is the second leading cause of cancer death in U.S. men after lung cancer. In the United Kingdom it is also the second most common cause of cancer death after lung cancer, where around 35,000 cases are diagnosed every year and of which around 10,000 die of it. Many factors, including genetics and diet, have been implicated in the development of prostate cancer. The Prostate Cancer Prevention Trial found that finasteride reduces the incidence of prostate cancer by 30%. There had been a controversy about this also increasing the risk of more aggressive cancers, but more recent research showed this may not be the case.[153][154]
More than 80% of men will develop prostate cancer by the age of 80.[155] However, in the majority of cases, it will be slow-growing and harmless. In such men, diagnosing prostate cancer is overdiagnosis—the needless identification of a technically aberrant condition that will never harm the patient—and treatment in such men exposes them to all of the adverse effects, with no possibility of extending their lives.[156]
In 1941, Charles B. Huggins published studies in which he used estrogen to oppose testosterone production in men with metastatic prostate cancer. This discovery of "chemical castration" won Huggins the 1966 Nobel Prize in Physiology or Medicine.[161] The role of the gonadotropin-releasing hormone (GnRH) in reproduction was determined by Andrzej W. Schally and Roger Guillemin, who both won the 1977 Nobel Prize in Physiology or Medicine for this work. GnRH receptor agonists, such as leuprolide and goserelin, were subsequently developed and used to treat prostate cancer.[162][163]
Radiation therapy for prostate cancer was first developed in the early 20th century and initially consisted of intraprostatic radium implants. External beam radiotherapy became more popular as stronger [X-ray] radiation sources became available in the middle of the 20th century. Brachytherapy with implanted seeds (for prostate cancer) was first described in 1983.[164]
Systemic chemotherapy for prostate cancer was first studied in the 1970s. The initial regimen of cyclophosphamide and 5-fluorouracil was quickly joined by multiple regimens using a host of other systemic chemotherapy drugs.[165]
Equality campaigners such as author Warren Farrell cite such stark spending inequalities as a clear example of governments unfairly favouring women's health over men's health.
Disparities also extend into areas such as detection, with governments failing to fund or mandate prostate cancer screening while fully supporting breast cancer programs. For example, a 2007 report found 49 U.S. states mandate insurance coverage for routine breast cancer screening, compared to 28 for prostate cancer.
Prostate cancer also experiences significantly less media coverage than other, equally prevalent cancers, with a study by Prostate Coalition showing 2.6 breast cancer stories for each one covering cancer of the prostate.
Prostate Cancer Awareness Month takes place in September in a number of countries. A light blue ribbon is used to promote the cause.
The study was stopped for ethical reasons to give the placebo group the same treatment. Apharadin uses bone targeted Radium-223 isotopes to kill cancer cells by alpha radiation.
Alpharadin is an investigational agent and is not approved for marketing by the European Medicines Agency (EMA), the U.S. Food and Drug Administration (FDA), or any other health authorities.
The LNCaP cancer cell line was established from a human lymph node metastatic lesion of prostatic adenocarcinoma. PC-3 and DU-145 cells were established from human prostatic adenocarcinoma metastatic to bone and to brain, respectively. LNCaP cells express androgen receptor (AR); however, PC-3 and DU-145 cells express very little or no AR.
AR, an androgen-activated transcription factor, belongs to the steroid nuclear receptor family. Development of the prostate is dependent on androgen signaling mediated through AR, and AR is also important during the development of prostate cancer.
The proliferation of LNCaP cells is androgen-dependent but the proliferation of PC-3 and DU-145 cells is androgen-insensitive. Elevation of AR expression is often observed in advanced prostate tumors in patients.
Some androgen-independent LNCaP sublines have been developed from the ATCC androgen-dependent LNCaP cells after androgen deprivation for study of prostate cancer progression.
These androgen-independent LNCaP cells have elevated AR expression and express prostate specific antigen upon androgen treatment. The paradox is that androgens inhibit the proliferation of these androgen-independent prostate cancer cells.
Another potential non-invasive method of early prostate tumor detection is through a molecular test that detects the presence of cell-associated PCA3 mRNA in fluid massaged from the prostate by the doctor and first-void urinated out within a limited amount of urine into the specimen container. PCA3 mRNA is expressed almost exclusively by prostate cells and has been shown to be highly over-expressed in prostate cancer cells.
The test result is currently reported as a specimen ratio of PCA3 mRNA to PSA mRNA. Although not a replacement for serum PSA level, the PCA3 test is an additional tool to help decide whether, in men suspected of having prostate cancer (especially if an initial biopsy fails to explain the elevated serum PSA), a biopsy/rebiopsy is really needed. The higher the expression of PCA3 in the sample, the greater the likelihood of a positive biopsy; i.e., the presence of cancer cells in the prostate.
Thrombophlebitis is associated with an increased risk of prostate cancer and may be a good way for physicians to remind themselves to screen patients with thrombophlebitis for prostate cancer as well since these two are closely linked.
pain, difficulty in urinating, problems during sexual intercourse, or erectile dysfunction. Other symptoms can potentially develop during later stages of the disease.
Rates of detection of prostate cancers vary widely across the world, with South and East Asia detecting less frequently than in Europe, and especially the United States.[3] Prostate cancer tends to develop in men over the age of fifty.[4] Globally it is the sixth leading cause of cancer-related death in men[5] (in the United States it is the second).[4] Prostate cancer is most common in the developed world with increasing rates in the developing world.[5] However, many men with prostate cancer never have symptoms, undergo no therapy, and eventually die of other unrelated causes. Many factors, including genetics and diet, have been implicated in the development of prostate cancer.
The presence of prostate cancer may be indicated by symptoms, physical examination, prostate-specific antigen (PSA), or biopsy. Prostate-specific antigen testing increases cancer detection but does not decrease mortality.[6] The United States Preventive Services Task Force in 2012 recommended against screening for prostate cancer using the PSA testing, due to the risk of over-diagnosis and over-treatment with most prostate cancer remaining asymptomatic.[7] The USPSTF concludes that the potential benefit of testing does not outweigh the expected harms.[7]
Management strategies for prostate cancer should be guided by the severity of the disease. Many low-risk tumors can be safely followed with active surveillance. Curative treatment generally involves surgery, various forms of radiation therapy, or, less commonly, cryosurgery; hormonal therapy and chemotherapy are generally reserved for cases of advanced disease (although hormonal therapy may be given with radiation in some cases). Several studies suggest that masturbation reduces the risk of prostate cancer.[8][9][10]
The age and underlying health of the man, the extent of metastasis, appearance under the microscope and response of the cancer to initial treatment are important in determining the outcome of the disease. The decision whether or not to treat localized prostate cancer (a tumor that is contained within the prostate) with curative intent is a patient trade-off between the expected beneficial and harmful effects in terms of patient survival and quality of life.
Signs and symptoms
Early prostate cancer usually causes no symptoms. Sometimes, however, prostate cancer does cause symptoms, often similar to those of diseases such as benign prostatic hyperplasia. These include frequent urination, nocturia (increased urination at night), difficulty starting and maintaining a steady stream of urine, hematuria (blood in the urine), and dysuria (painful urination). About a third of patients diagnosed with prostate cancer have one or more such symptoms, while two thirds have no symptoms.[11]Prostate cancer is associated with urinary dysfunction as the prostate gland surrounds the prostatic urethra. Changes within the gland, therefore, directly affect urinary function. Because the vas deferens deposits seminal fluid into the prostatic urethra, and secretions from the prostate gland itself are included in semen content, prostate cancer may also cause problems with sexual function and performance, such as difficulty achieving erection or painful ejaculation.[11]
Advanced prostate cancer can spread to other parts of the body, possibly causing additional symptoms. The most common symptom is bone pain, often in the vertebrae (bones of the spine), pelvis, or ribs. Spread of cancer into other bones such as the femur is usually to the proximal part of the bone. Prostate cancer in the spine can also compress the spinal cord, causing leg weakness and urinary and fecal incontinence.[12]
Risk factors
A complete understanding of the causes of prostate cancer remains elusive.[13] The primary risk factors are obesity, age and family history. Prostate cancer is very uncommon in men younger than 45, but becomes more common with advancing age. The average age at the time of diagnosis is 70.[14] However, many men never know they have prostate cancer. Autopsy studies of Chinese, German, Israeli, Jamaican, Swedish, and Ugandan men who died of other causes have found prostate cancer in thirty percent of men in their 50s, and in eighty percent of men in their 70s.[15] Men who have first-degree family members with prostate cancer appear to have double the risk of getting the disease compared to men without prostate cancer in the family.[16] This risk appears to be greater for men with an affected brother than for men with an affected father. In the United States in 2005, there were an estimated 230,000 new cases of prostate cancer and 30,000 deaths due to prostate cancer.[17] Men with high blood pressure are more likely to develop prostate cancer.[18] There is a small increased risk of prostate cancer associated with lack of exercise.[19] A 2010 study found that prostate basal cells were the most common site of origin for prostate cancers.[20]Genetic
Genetic background may contribute to prostate cancer risk, as suggested by associations with race, family, and specific gene variants. Men who have a first-degree relative (father or brother) with prostate cancer have twice the risk of developing prostate cancer, and those with two first-degree relatives affected have a fivefold greater risk compared with men with no family history.[21] In the United States, prostate cancer more commonly affects black men than white or Hispanic men, and is also more deadly in black men.[22] [23] In contrast, the incidence and mortality rates for Hispanic men are one third lower than for non-Hispanic whites. Studies of twins in Scandinavia suggest that forty percent of prostate cancer risk can be explained by inherited factors.[24]No single gene is responsible for prostate cancer; many different genes have been implicated. Mutations in BRCA1 and BRCA2, important risk factors for ovarian cancer and breast cancer in women, have also been implicated in prostate cancer.[25] Other linked genes include the Hereditary Prostate cancer gene 1 (HPC1), the androgen receptor, and the vitamin D receptor.[22] TMPRSS2-ETS gene family fusion, specifically TMPRSS2-ERG or TMPRSS2-ETV1/4 promotes cancer cell growth.[26]
Loss of cancer suppressor genes, early in the prostatic carcinogenesis, have been localized to chromosomes 8p, 10q, 13q,and 16q. P53 mutations in the primary prostate cancer are relatively low and are more frequently seen in metastatic settings, hence, p53 mutations are late event in pathology of prostate cancer. Other tumor suppressor genes that are thought to play a role in prostate cancer include PTEN (gene) and KAI1. "Up to 70 percent of men with prostate cancer have lost one copy of the PTEN gene at the time of diagnosis"[27] Relative frequency of loss of E-cadherin and CD44 has also been observed.
Two large genome-wide association studies linking single nucleotide polymorphisms (SNPs) to prostate cancer were published in 2008.[28][29] These studies identified several SNPs which substantially affect the risk of prostate cancer. For example, individuals with TT allele pair at SNP rs10993994 were reported to be at 1.6 times higher risk of prostate cancer than those with the CC allele pair. This SNP explains part of the increased prostate cancer risk of African American men as compared to American men of European descent, since the C allele is much more prevalent in the latter; this SNP is located in the promoter region of the MSMB gene, thus affects the amount of MSMB protein synthesized and secreted by epithelial cells of the prostate.[30]
Dietary
While some dietary factors have been associated with prostate cancer the evidence is still tentative.[31] Evidence supports little role for dietary fruits and vegetables in prostate cancer occurrence.[32] Red meat and processed meat also appear to have little effect in human studies.[33] Higher meat consumption has been associated with a higher risk in some studies.[34]Lower blood levels of vitamin D may increase the risk of developing prostate cancer.[35]
Taking multivitamins more than seven times a week may increase the risk of developing the disease.[36][37][non-primary source needed]
A 2009 study on folic acid supplements showed an association with an increased risk of developing prostate cancer.[38][non-primary source needed]
Medication exposure
There are also some links between prostate cancer and medications, medical procedures, and medical conditions.[39] Use of the cholesterol-lowering drugs known as the statins may also decrease prostate cancer risk.[40]Infection or inflammation of the prostate (prostatitis) may increase the chance for prostate cancer while another study shows infection may help prevent prostate cancer by increasing blood to the area. In particular, infection with the sexually transmitted infections chlamydia, gonorrhea, or syphilis seems to increase risk.[41] Finally, obesity[42] and elevated blood levels of testosterone[43] may increase the risk for prostate cancer. There is an association between vasectomy and prostate cancer however more research is needed to determine if this is a causative relationship.[44]
Research released in May 2007, found that US war veterans who had been exposed to Agent Orange had a 48% increased risk of prostate cancer recurrence following surgery.[45]
Viral
In 2006, a previously unknown retrovirus, Xenotropic MuLV-related virus or XMRV, was associated with human prostate tumors,[46] but subsequent reports on the virus were contradictory,[47][48] and the original 2006 finding was instead due to a previously undetected contamination.[49] The journals Science and PlosONE both retracted XMRV related articles.[50][51]Sexual factors
Several case-control studies have shown that having many lifetime sexual partners or starting sexual activity early in life substantially increases the risk of prostate cancer.[52][53][54] This correlation suggests a sexually transmissible infection (STI) may cause some prostate cancer cases; however, many studies have unsuccessfully attempted to find such a link, especially when testing for STIs shortly before or after prostate cancer diagnosis.[55][56] Studies testing for STIs a decade or more prior to prostate cancer diagnosis find a significant link between prostate cancer and various STIs (HPV-16, HPV-18 and HSV-2).[57][58][59] This evidence could be explained by a yet-to-be-identified sexually transmissible infection and a long latency period between onset of infection and clinical prostate cancer.[53][55][56]Pathophysiology
The prostate is a zinc accumulating, citrate producing organ. The protein ZIP1 is responsible for the active transport of zinc into prostate cells. One of zinc's important roles is to change the metabolism of the cell in order to produce citrate, an important component of semen. The process of zinc accumulation, alteration of metabolism, and citrate production is energy inefficient, and prostate cells sacrifice enormous amounts of energy (ATP) in order to accomplish this task. Prostate cancer cells are generally devoid of zinc. This allows prostate cancer cells to save energy not making citrate, and utilize the new abundance of energy to grow and spread. The absence of zinc is thought to occur via a silencing of the gene that produces the transporter protein ZIP1. ZIP1 is now called a tumor suppressor gene product for the gene SLC39A1. The cause of the epigenetic silencing is unknown. Strategies which transport zinc into transformed prostate cells effectively eliminate these cells in animals. Zinc inhibits NF-ÎşB pathways, is anti-proliferative, and induces apoptosis in abnormal cells. Unfortunately, oral ingestion of zinc is ineffective since high concentrations of zinc into prostate cells is not possible without the active transporter, ZIP1.[64]
RUNX2 is a transcription factor that prevents cancer cells from undergoing apoptosis thereby contributing to the development of prostate cancer.[65]
The PI3k/Akt signaling cascade works with the transforming growth factor beta/SMAD signaling cascade to ensure prostate cancer cell survival and protection against apoptosis.[66] X-linked inhibitor of apoptosis (XIAP) is hypothesized to promote prostate cancer cell survival and growth and is a target of research because if this inhibitor can be shut down then the apoptosis cascade can carry on its function in preventing cancer cell proliferation.[67] Macrophage inhibitory cytokine-1 (MIC-1) stimulates the focal adhesion kinase (FAK) signaling pathway which leads to prostate cancer cell growth and survival.[68]
The androgen receptor helps prostate cancer cells to survive and is a target for many anti cancer research studies; so far, inhibiting the androgen receptor has only proven to be effective in mouse studies.[69] Prostate specific membrane antigen (PSMA) stimulates the development of prostate cancer by increasing folate levels for the cancer cells to use to survive and grow; PSMA increases available folates for use by hydrolyzing glutamated folates.[70]
Diagnosis
The American Cancer Society's position regarding early detection is "Research has not yet proven that the potential benefits of testing outweigh the harms of testing and treatment. The American Cancer Society believes that men should not be tested without learning about what we know and don’t know about the risks and possible benefits of testing and treatment. Starting at age 50, (45 if African American or brother or father suffered from condition before age 65) talk to your doctor about the pros and cons of testing so you can decide if testing is the right choice for you."[71]The only test that can fully confirm the diagnosis of prostate cancer is a biopsy, the removal of small pieces of the prostate for microscopic examination. However, prior to a biopsy, less invasive testing can be conducted.
According to Professor Hardev Pandha, The Prostate Project Chair of Urological Oncology at the University of Surrey's Postgraduate Medical School, a non-invasive test looking for the presence of the protein Engrailed-2 (EN2) in the urine to be more reliable and accurate than existing tests.
"In this study, we showed that the new test was twice as good at finding prostate cancer as the standard PSA test. Only rarely did we find EN2 in the urine of men who were cancer free, so if we find EN2 we can be reasonably sure that a man has prostate cancer. EN2 was not detected in men with non-cancer disorders of the prostate such as prostatitis or benign enlargement. These conditions often cause a high PSA result, causing considerable stress for the patient and sometimes also unnecessary further tests such as prostate biopsies." [72]
There are also several other tests that can be used to gather more information about the prostate and the urinary tract. Digital rectal examination (DRE) may allow a doctor to detect prostate abnormalities. Cystoscopy shows the urinary tract from inside the bladder, using a thin, flexible camera tube inserted down the urethra. Transrectal ultrasonography creates a picture of the prostate using sound waves from a probe in the rectum.
Prostate imaging
Ultrasound (US) and Magnetic Resonance Imaging (MRI) are the two main imaging methods used for prostate cancer detection. Urologists use transrectal ultrasound during prostate biopsy and can sometimes see a hypoechoic area (tissues or structures that reflect relatively less of the ultrasound waves directed at them). But US has poor tissue resolution and thus, is generally not clinically used. In contrast, prostate MRI has superior soft tissue resolution. MRI is a type of imaging that uses magnetic fields to locate and characterize prostate cancer. Multi-parametric prostate MRI consists of four types of MRI sequences called T2 weighted imaging, T1 weighted imaging, Diffusion Weighted Imaging, MR Spectrocopic Imaging and Dynamic-Contrast Enhanced Imaging.[73] Genitourinary radiologists use multi-parametric MRI to locate and identify prostate cancer. Currently, MRI is used to identify targets for prostate biopsy using fusion MRI with ultrasound (US) or MRI-guidance alone. In men who are candidates for active surveillance, fusion MR/US guided prostate biopsy detected 33% of cancers compared to 7% with standard ultrasound guided biopsy.[74] Prostate MRI is also used for surgical planning for men undergoing robotic prostatectomy. It has also shown to help surgeons decide whether to resect or spare the neurovascular bundle, determine return to urinary continence and help assess surgical difficulty.[75] Some prostate advocacy groups believe prostate MRI should be used to screen for prostate cancer--"manogram"—like mammogram is for breast cancer. NIH-funded clinical trials are underway to delineate the value of MRI for some of these applications.[76]Biopsy
Main article: Prostate biopsy
Gleason score
Main article: Gleason score
The tissue samples are then examined under a microscope to determine
whether cancer cells are present, and to evaluate the microscopic
features (or Gleason score) of any cancer found. Prostate specific membrane antigen is a transmembrane carboxypeptidase and exhibits folate hydrolase activity.[38] This protein is overexpressed in prostate cancer tissues and is associated with a higher Gleason score.[38]Tumor markers
Tissue samples can be stained for the presence of PSA and other tumor markers in order to determine the origin of malignant cells that have metastasized.[78]Small cell carcinoma is a very rare (1%[79]) type of prostate cancer that cannot be diagnosed using the PSA.[79][80] As of 2009 researchers are trying to determine the best way to screen for this type of prostate cancer because it is a relatively unknown and rare type of prostate cancer but very serious and quick to spread to other parts of the body.[80] Possible methods include chromatographic separation methods by mass spectrometry, or protein capturing by immunoassays or immunized antibodies. The test method will involve quantifying the amount of the biomarker PCI, with reference to the Gleason Score. Not only is this test quick, it is also sensitive. It can detect patients in the diagnostic grey zone, particularly those with a serum free to total Prostate Specific Antigen ratio of 10-20%.[81]
The oncoprotein BCL-2, has been associated with the development of androgen-independent prostate cancer due to its high levels of expression in androgen-independent tumours in advanced stages of the pathology. The upregulation of BCL-2 after androgen ablation in prostate carcinoma cell lines and in a castrated-male rat model further established a connection between BCL-2 expression and prostate cancer progression.[82]
The expression of Ki-67 by immunohistochemistry may be a significant predictor of patient outcome for men with prostate cancer.[83]
ERK5 is a protein that may be used as a marker. ERK5 is present in abnormally high levels of prostate cancer, including invasive cancer which has spread to other parts of the body. It is also present in relapsed cancer following previous hormone therapy. Research shows that reducing the amount of ERK5 found in cancerous cells reduces their invasiveness.[84]
Classification
Main article: Prostate cancer staging
An important part of evaluating prostate cancer is determining the stage, or how far the cancer has spread. Knowing the stage helps define prognosis and is useful when selecting therapies. The most common system is the four-stage TNM system (abbreviated from Tumor/Nodes/Metastases). Its components include the size of the tumor, the number of involved lymph nodes, and the presence of any other metastases.[85]The most important distinction made by any staging system is whether or not the cancer is still confined to the prostate. In the TNM system, clinical T1 and T2 cancers are found only in the prostate, while T3 and T4 cancers have spread elsewhere. Several tests can be used to look for evidence of spread. Medical specialty professional organizations recommend against the use of PET scans, CT scans, or bone scans when a physician stages early prostate cancer with low risk for metastasis.[86][87] Those tests would be appropriate in such cases as when a CT scan evaluates spread within the pelvis, a bone scan look for spread to the bones, and endorectal coil magnetic resonance imaging to closely evaluate the prostatic capsule and the seminal vesicles. Bone scans should reveal osteoblastic appearance due to increased bone density in the areas of bone metastasis—opposite to what is found in many other cancers that metastasize.
After a prostate biopsy, a pathologist looks at the samples under a microscope. If cancer is present, the pathologist reports the grade of the tumor. The grade tells how much the tumor tissue differs from normal prostate tissue and suggests how fast the tumor is likely to grow. The Gleason system is used to grade prostate tumors from 2 to 10, where a Gleason score of 10 indicates the most abnormalities. The pathologist assigns a number from 1 to 5 for the most common pattern observed under the microscope, then does the same for the second-most-common pattern. The sum of these two numbers is the Gleason score. The Whitmore-Jewett stage is another method sometimes used.
Prevention
Diet and lifestyle
The data on the relationship between diet and prostate cancer is poor.[88] In light of this the incidence of prostate cancer is correlated with the consumption of the Western diet.[88] Trans fats, saturated fats, and carbohydrates may be associated with an increased risk,[89][88] and while Omega-3 fatty acids may result in some benefit, the evidence is inconclusive.[88][90] Vitamin supplements appear to have no effect and some may increase the risk.[91][88] High calcium intake has been linked to advanced prostate cancer.[92] Consuming fish may lower prostate cancer deaths but does not appear to affect its occurrence.[93] Some evidence supports lower rates of prostate cancer with a vegetarian diet.[94] There is some tentative evidence for foods containing lycopene and selenium.[95] Diets rich in cruciferous vegetables, soy, beans and other legumes may be associated with a lower risk of prostate cancer, especially more advanced cancers.[96]While the available evidence is weak,[97] tentative results suggest that frequent ejaculation may decrease the risk of prostate cancer.[98] Men who get regular exercise may have a slightly lower risk, especially vigorous activity and the risk of advanced prostate cancer.[96]
Medications
In those who are being regularly screened 5-alpha-reductase inhibitor (finasteride and dutasteride) reduce the overall risk of being diagnosed with prostate cancer however there is insufficient data to determine if they have an effect on the risk of death and may increase the chance of more serious cases.[99]Screening
Main article: Prostate cancer screening
Prostate cancer screening is an attempt to find unsuspected cancers, and may lead to more invasive follow-up tests such as a biopsy, with cell samples taken for closer study. Options include the digital rectal exam (DRE) and the prostate-specific antigen (PSA) blood test. Such screening is controversial and, in some people, may lead to unnecessary, possibly harmful, consequences.[100] Routine screening with either a DRE or PSA is not supported by the evidence as there is no mortality benefit from screening.[6]The United States Preventive Services Task Force (USPSTF) recommends against the PSA test for prostate cancer screening in healthy men regardless of age.[101] They conclude that the potential benefit of testing does not outweigh the expected harms.[7][102] The Centers for Disease Control and Prevention shared that conclusion.[103] The American Society of Clinical Oncology recommends screening be discouraged in those who are expected to live less than ten years, while in those with a life expectancy of greater than ten years a decision should be made by the person in question based on the potential risks and benefits.[104]
Management
Main article: Management of prostate cancer
The first decision to be made in managing prostate cancer is whether
treatment is needed. Prostate cancer, especially low-grade forms found
in the elderly, often grows slowly that no treatment is required.[105]
Treatment may also be inappropriate if a person has other serious
health problems or is not expected to live long enough for symptoms to
appear.Which option is best depends on the stage of the disease, the Gleason score, and the PSA level. Other important factors are age, general health, and a person's views about potential treatments and their possible side effects. Because all treatments can have significant side effects, such as erectile dysfunction and urinary incontinence, treatment discussions often focus on balancing the goals of therapy with the risks of lifestyle alterations. A combination of the treatment options is often recommended for managing prostate cancer.[106][107][108]
Guidelines for treatment for specific clinical situations requires a good estimation of a person's long-term life expectancy.[109] People can also use an 18-item questionnaire to learn whether they have good knowledge and understanding about their treatment options before they choose. Most of those who are newly diagnosed and made a treatment choice can not correctly answer over half of the questions.[109]
If radiation therapy is done first, and fails, then radical prostatectomy is very technically challenging surgery and may not be feasible. On the other hand, radiation therapy done after surgical failure may have many complications.[110]
In localized disease it is unknown if radical prostatectomy is better or worse than watchful waiting.[111]
Surveillance
Many men diagnosed with low-risk prostate cancer are eligible for active surveillance. This term implies careful observation of the tumor over time, with the intention of treatment for cure if there are signs of cancer progression. Active surveillance is not synonymous with watchful waiting, an older term which implies no treatment or specific program of monitoring, with the assumption that palliative, not curative, treatment would be used if advanced, symptomatic disease develops.Active surveillance involves monitoring the tumor for signs of growth or the appearance of symptoms. The monitoring process may involve serial PSA, physical examination of the prostate, and/or repeated biopsies. The goal of surveillance is to avoid overtreatment and the sometimes serious, permanent side effects of treatment for a slow-growing or self-limited tumor that would never cause any problems for the patient. This approach is not used for aggressive cancers, but it may cause anxiety for patients who wrongly believe that all cancer is deadly or themselves to have a life-threatening cancer.
For 50% to 75% of people with prostate cancer it will cause no harm before a person dies.[112]
Aggressive cancer
Treatment of aggressive prostate cancers may involve surgery (i.e. radical prostatectomy), radiation therapy including brachytherapy (prostate brachytherapy) and external beam radiation therapy, High-intensity focused ultrasound (HIFU), chemotherapy, oral chemotherapeutic drugs (Temozolomide/TMZ), cryosurgery, hormonal therapy, or some combination.[113][114]Although the widespread use of prostate specific antigen (PSA) screening in the USA has resulted in diagnosis at earlier age and cancer stage, the vast majority of cases are still diagnosed in men older than 65 years, and approximately 25% of cases are diagnosed in men older than 75 years.[115] Though US National Comprehensive Cancer Network guidelines[116] recommend using life expectancy greater than or less than 10 years to help make treatment decisions, in practice, many elderly patients are not offered curative treatment options such as radical prostatectomy or radiation therapy and are instead treated with hormonal therapy or watchful waiting. This pattern can be attributed to factors such as medical co-morbidity and patient preferences is regard to quality of life in addition to prostate cancer specific risk factors such as pretreatment PSA, Gleason score and clinical stage. As the average life expectancy increases due to advances in treatment of cardiovascular, pulmonary and other chronic disease, it is likely that more elderly patients will be living long enough to suffer the consequences of their prostate cancer. Therefore, there is currently much interest in the role of aggressive prostate cancer treatment modalities such as with surgery or radiation in the elderly population who have localized disease. The results of one randomized controlled trial published by the Scandinavian Prostate Cancer Group 4 [117] evaluated cancer-specific mortality in patients treated with RP compared with watchful waiting. The patients receiving radical prostatectomy had a relative risk reduction of 30.7% [95% confidence interval 2.5%-50.7%], but an absolute risk reduction of 6% [95% confidence interval 0.5%-11.5%]. The number needed to treat was calculated to be 16. This means that, over the median follow up period of approximately 10 years, 16 patients with localized prostate cancer would need to receive radical prostatectomy rather than watchful waiting in order to prevent one death due to prostate cancer. Further subset analysis revealed that this benefit did not apply to all ages equally. In men younger than 65 years, patients randomized to receive radical prostatectomy actually had a 10-18% absolute risk reduction in cancer-specific mortality compared to those randomized to watchful waiting. However, in men older than 65, there was no statistically significant risk reduction even when adjusted for PSA level, Gleason score and tumor stage. Randomized, controlled trials comparing radical prostatectomy, radiation therapy, hormonal therapy and watchful waiting would provide the best evidence for how to best treat elderly patients.
If the cancer has spread beyond the prostate, treatment options significantly change, so most doctors that treat prostate cancer use a variety of nomograms to predict the probability of spread. Treatment by watchful waiting/active surveillance, external beam radiation therapy, brachytherapy, cryosurgery, HIFU, and surgery are, in general, offered to men whose cancer remains within the prostate. Hormonal therapy and chemotherapy are often reserved for disease that has spread beyond the prostate. However, there are exceptions: radiation therapy may be used for some advanced tumors, and hormonal therapy is used for some early stage tumors. Cryotherapy (the process of freezing the tumor), hormonal therapy, and chemotherapy may also be offered if initial treatment fails and the cancer progresses.
Sipuleucel-T has been found result in a benefit ( a four month increase in survival ) for men with metastatic prostate cancer.[118]
Castration-resistant
Most hormone dependent cancers become refractory after one to three years and resume growth despite hormone therapy. Previously considered "hormone-refractory prostate cancer" or "androgen-independent prostate cancer", the term castration-resistant has replaced "hormone refractory" because while they are no longer responsive to castration treatment (reduction of available androgen/testosterone/DHT by chemical or surgical means), these cancers still show reliance upon hormones for androgen receptor activation.[119] Before 2004, all treatments for castration-resistant prostate cancer (CRPC) were considered[who?] palliative and not shown to prolong survival.[citation needed] However, there are now several treatments available to treat CRPC that improve survival.The cancer chemotherapic docetaxel has been used as treatment for CRPC with a median survival benefit of 2 to 3 months.[120][121] A second-line chemotherapy treatment is cabazitaxel.[122]
Off-label use of the oral drug ketoconazole is sometimes used as a way to further manipulate hormones with a therapeutic effect in CRPC. However, many side effects are possible with this drug and abiraterone is likely to supplant usage since it has a similar mechanism of action with less toxic side effects.
A combination of bevacizumab (Avastin), docetaxel, thalidomide and prednisone appears effective in the treatment of CRPC.[123]
The immunotherapy treatment with sipuleucel-T is also effective in the treatment of CRPC with a median survival benefit of 4.1 months.[124]
The second line hormonal therapy abiraterone (Zytiga) increased overall survival increased by 4.6 months when compared to placebo. Abiraterone acetate in combination with prednisone to treat people with late-stage (metastatic) castration-resistant prostate cancer who have received prior docetaxel (chemotherapy).[125] Enzalutamide is another second line hormonal agent which has demonstrated a 5 month survival advantage over placebo. Both abiraterone and enzalutamide are currently being tested in clinical trials with CRPC patients who have not previously received chemotherapy.
Only a subset of a patient respond to androgen signaling blocking drugs and certain cells with characteristics resembling stem cells remain unaffected.[126][127] Therefore, the desire to improve outcome of CRPC patients has resulted into the claims of increasing doses further or combination therapy with synergistic androgen signaling blocking agents.[128] But even these combination will not affect stem -like cells that do not exhibit androgen signaling. It is possible that for further advances, a combination of androgen signaling blocking agent with stem-like cell directed differentiation therapy drug would prove ideal.[129]
Prognosis
Prostate cancer rates are higher and prognoses are poorer in developed countries than in the rest of the world. Many of the risk factors for prostate cancer are more prevalent in the developed world, including longer life expectancy and diets high in red meat. (People who consume larger amounts of meat and dairy also tend to consume fewer portions of fruits and vegetables. It is not currently clear whether both of these factors, or just one of them, contribute to the occurrence of prostate cancer.[130]) Also, where there is more access to screening programs, there is a higher detection rate. Prostate cancer is the ninth-most-common cancer in the world, but is the number-one non-skin cancer in men from the United States. Prostate cancer affected 18 percent of American men and caused death in three percent in 2005.[17] In Japan, death from prostate cancer was one-fifth to one-half the rates in the United States and Europe in the 1990s.[131] In India in the 1990s, half of the people with prostate cancer confined to the prostate died within ten years.[132] African-American men have 50–60 times more prostate cancer and prostate cancer deaths than men in Shanghai, China.[133] In Nigeria, two percent of men develop prostate cancer, and 64% of them are dead after two years.[134]In patients who undergo treatment, the most important clinical prognostic indicators of disease outcome are stage, pre-therapy PSA level, and Gleason score. In general, the higher the grade and the stage, the poorer the prognosis. Nomograms can be used to calculate the estimated risk of the individual patient. The predictions are based on the experience of large groups of patients suffering from cancers at various stages.[135]
In 1941, Charles Huggins reported that androgen ablation therapy causes regression of primary and metastatic androgen-dependent prostate cancer.[136] He was awarded the 1966 Nobel Prize for Physiology or Medicine for this discovery. Androgen ablation therapy causes remission in 80-90% of patients undergoing therapy, resulting in a median progression-free survival of 12 to 33 months. After remission, an androgen-independent phenotype typically emerges, wherein the median overall survival is 23–37 months from the time of initiation of androgen ablation therapy.[137] The actual mechanism contributes to the progression of prostate cancer is not clear and may vary between individual patient. A few possible mechanisms have been proposed.[138]
Classification systems
Many prostate cancers are not destined to be lethal, and most men will ultimately die from causes other than of the disease. Decisions about treatment type and timing may, therefore, be informed by an estimation of the risk that the tumor will ultimately recur after treatment and/or progress to metastases and mortality. Several tools are available to help predict outcomes, such as pathologic stage and recurrence after surgery or radiation therapy. Most combine stage, grade, and PSA level, and some also add the number or percent of biopsy cores positive, age, and/or other information.- The D'Amico classification stratifies men by low, intermediate, or high risk based on stage, grade, and PSA. It is used widely in clinical practice and research settings. The major downside to the 3-level system is that it does not account for multiple adverse parameters (e.g., high Gleason score and high PSA) in stratifying patients.
- The Partin tables predict pathologic outcomes (margin status, extraprostatic extension, and seminal vesicle invasion) based on the same three variables and are published as lookup tables.
- The Kattan nomograms predict recurrence after surgery and/or radiation therapy, based on data available either at time of diagnosis or after surgery. The nomograms can be calculated using paper graphs or software available on a website or for handheld computers. The Kattan score represents the likelihood of remaining free of disease at a given time interval following treatment.
- The UCSF Cancer of the Prostate Risk Assessment (CAPRA) score predicts both pathologic status and recurrence after surgery. It offers comparable accuracy as the Kattan preoperative nomogram, and can be calculated without paper tables or a calculator. Points are assigned based on PSA, Grade, stage, age, and percent of cores positive; the sum yields a 0–10 score, with every 2 points representing roughly a doubling of risk of recurrence. The CAPRA score was derived from community-based data in the CaPSURE database. It has been validated among over 10,000 prostatectomy patients, including patients from CaPSURE;[139] the SEARCH registry, representing data from several Veterans Administration and active military medical centers;[140] a multi-institutional cohort in Germany;[141] and the prostatectomy cohort at Johns Hopkins University.[142] More recently, it has been shown to predict metastasis and mortality following prostatectomy, radiation therapy, watchful waiting, or androgen deprivation therapy.[143]
Epidemiology
no data
less than 4
4-8
8-12
12-16
16-20
20-24
24-28
28-32
32-36
36-40
40-44
more than 44
Prostate cancer develops primarily in men over fifty. It is the most common type of cancer in men in the United States, with 186,000 new cases in 2008 and 28,600 deaths.[152] It is the second leading cause of cancer death in U.S. men after lung cancer. In the United Kingdom it is also the second most common cause of cancer death after lung cancer, where around 35,000 cases are diagnosed every year and of which around 10,000 die of it. Many factors, including genetics and diet, have been implicated in the development of prostate cancer. The Prostate Cancer Prevention Trial found that finasteride reduces the incidence of prostate cancer by 30%. There had been a controversy about this also increasing the risk of more aggressive cancers, but more recent research showed this may not be the case.[153][154]
More than 80% of men will develop prostate cancer by the age of 80.[155] However, in the majority of cases, it will be slow-growing and harmless. In such men, diagnosing prostate cancer is overdiagnosis—the needless identification of a technically aberrant condition that will never harm the patient—and treatment in such men exposes them to all of the adverse effects, with no possibility of extending their lives.[156]
History
Although the prostate was first described by Venetian anatomist Niccolò Massa in 1536, and illustrated by Flemish anatomist Andreas Vesalius in 1538, prostate cancer was not identified until 1853.[157] Prostate cancer was initially considered a rare disease, probably because of shorter life expectancies and poorer detection methods in the 19th century. The first treatments of prostate cancer were surgeries to relieve urinary obstruction.[158] Removal of the entire gland (radical perineal prostatectomy) was first performed in 1904 by Hugh H. Young at Johns Hopkins Hospital.[159] Surgical removal of the testes (orchiectomy) to treat prostate cancer was first performed in the 1890s, but with limited success. Transurethral resection of the prostate (TURP) replaced radical prostatectomy for symptomatic relief of obstruction in the middle of the 20th century because it could better preserve penile erectile function. Radical retropubic prostatectomy was developed in 1983 by Patrick Walsh.[160] This surgical approach allowed for removal of the prostate and lymph nodes with maintenance of penile function.In 1941, Charles B. Huggins published studies in which he used estrogen to oppose testosterone production in men with metastatic prostate cancer. This discovery of "chemical castration" won Huggins the 1966 Nobel Prize in Physiology or Medicine.[161] The role of the gonadotropin-releasing hormone (GnRH) in reproduction was determined by Andrzej W. Schally and Roger Guillemin, who both won the 1977 Nobel Prize in Physiology or Medicine for this work. GnRH receptor agonists, such as leuprolide and goserelin, were subsequently developed and used to treat prostate cancer.[162][163]
Radiation therapy for prostate cancer was first developed in the early 20th century and initially consisted of intraprostatic radium implants. External beam radiotherapy became more popular as stronger [X-ray] radiation sources became available in the middle of the 20th century. Brachytherapy with implanted seeds (for prostate cancer) was first described in 1983.[164]
Systemic chemotherapy for prostate cancer was first studied in the 1970s. The initial regimen of cyclophosphamide and 5-fluorouracil was quickly joined by multiple regimens using a host of other systemic chemotherapy drugs.[165]
Cell-of-origin
A series of studies published in Science involved introduced viruses known to cause cancerous mutation in prostate cells: AKT, ERG, and AR into isolated samples of basal and luminal cells and grafted the treated tissue into mice. After 16 weeks, none of the luminal samples had undergone malignant mutation, while the basal samples had mutated into prostate-like tubules which had then developed malignancy and formed cancerous tumors, which appeared identical to human samples under magnification. This led to the conclusion that the prostate basal cell may be the most likely "site of origin" of prostate cancer.[20]Society and culture
People with prostate cancer generally encounter significant disparities in awareness, funding, media coverage, and research—and therefore, inferior treatment and poorer outcomes—compared to other cancers of equal prevalence.[166] In 2001, The Guardian noted that Britain had 3,000 nurses specializing in breast cancer, compared to only one for prostate cancer. It also discovered that the waiting time between referral and diagnosis was two weeks for breast cancer but three months for prostate cancer. A 2007 report by the U.S.-based National Prostate Cancer Coalition stated that for every prostate cancer drug on the market, there were seven used to treat breast cancer. The Times also noted an "anti-male bias in cancer funding" with a four to one discrepancy in the United Kingdom by both the government and by cancer charities such as Cancer Research UK.Equality campaigners such as author Warren Farrell cite such stark spending inequalities as a clear example of governments unfairly favouring women's health over men's health.
Disparities also extend into areas such as detection, with governments failing to fund or mandate prostate cancer screening while fully supporting breast cancer programs. For example, a 2007 report found 49 U.S. states mandate insurance coverage for routine breast cancer screening, compared to 28 for prostate cancer.
Prostate cancer also experiences significantly less media coverage than other, equally prevalent cancers, with a study by Prostate Coalition showing 2.6 breast cancer stories for each one covering cancer of the prostate.
Prostate Cancer Awareness Month takes place in September in a number of countries. A light blue ribbon is used to promote the cause.
Research
A genistein derivative KBU2046 is under investigation for prostate cancer. MDV3100 is in phase III trials for HRPC (chemo-naive and post-chemo patient populations). Alpharadin completed a phase 3 trial for CRPC patients with bone metastasis. A pre-planned interim analysis showed improved survival and quality of life.The study was stopped for ethical reasons to give the placebo group the same treatment. Apharadin uses bone targeted Radium-223 isotopes to kill cancer cells by alpha radiation.
Alpharadin is an investigational agent and is not approved for marketing by the European Medicines Agency (EMA), the U.S. Food and Drug Administration (FDA), or any other health authorities.
Prostate cancer models
Scientists have established a few prostate cancer cell lines to investigate the mechanism involved in the progression of prostate cancer. LNCaP, PC-3 (PC3), and DU-145 (DU145) are commonly used prostate cancer cell lines.The LNCaP cancer cell line was established from a human lymph node metastatic lesion of prostatic adenocarcinoma. PC-3 and DU-145 cells were established from human prostatic adenocarcinoma metastatic to bone and to brain, respectively. LNCaP cells express androgen receptor (AR); however, PC-3 and DU-145 cells express very little or no AR.
AR, an androgen-activated transcription factor, belongs to the steroid nuclear receptor family. Development of the prostate is dependent on androgen signaling mediated through AR, and AR is also important during the development of prostate cancer.
The proliferation of LNCaP cells is androgen-dependent but the proliferation of PC-3 and DU-145 cells is androgen-insensitive. Elevation of AR expression is often observed in advanced prostate tumors in patients.
Some androgen-independent LNCaP sublines have been developed from the ATCC androgen-dependent LNCaP cells after androgen deprivation for study of prostate cancer progression.
These androgen-independent LNCaP cells have elevated AR expression and express prostate specific antigen upon androgen treatment. The paradox is that androgens inhibit the proliferation of these androgen-independent prostate cancer cells.
Diagnosis
At present, an active area of research and non-clinically applied investigations involve non-invasive methods of prostate tumor detection. Adenoviruses modified to transfect tumor cells with harmless yet distinct genes (such as luciferase) have proven capable of early detection. So far, however, this area of research has been tested only in animal and LNCaP cell models.- Gene
Another potential non-invasive method of early prostate tumor detection is through a molecular test that detects the presence of cell-associated PCA3 mRNA in fluid massaged from the prostate by the doctor and first-void urinated out within a limited amount of urine into the specimen container. PCA3 mRNA is expressed almost exclusively by prostate cells and has been shown to be highly over-expressed in prostate cancer cells.
The test result is currently reported as a specimen ratio of PCA3 mRNA to PSA mRNA. Although not a replacement for serum PSA level, the PCA3 test is an additional tool to help decide whether, in men suspected of having prostate cancer (especially if an initial biopsy fails to explain the elevated serum PSA), a biopsy/rebiopsy is really needed. The higher the expression of PCA3 in the sample, the greater the likelihood of a positive biopsy; i.e., the presence of cancer cells in the prostate.
- Early prostate cancer antigen
Thrombophlebitis is associated with an increased risk of prostate cancer and may be a good way for physicians to remind themselves to screen patients with thrombophlebitis for prostate cancer as well since these two are closely linked.
- Prostasomes
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