Note: Separate PDQ summaries on Prostate Cancer Screening, Prostate Cancer Treatment, and Levels of Evidence for Cancer Screening and Prevention Studies are also available.
Chemoprevention with finasteride and dutasteride reduces the incidence of prostate cancer, but the evidence is inadequate to determine whether chemoprevention with finasteride or dutasteride reduces mortality from prostate cancer.
In the dutasteride trial, using the restricted crude rate absolute risk reduction was 5.1% at 4 years, and RRR was 22.8% (95% CI, 15.2%–29.8%; P < .001). There was no difference in prostate cancer or overall mortality, although the number of deaths was small and none were due to prostate cancer. The reduction in prostate cancer incidence occurred primarily in Gleason 5 to 6 cancers.  The reduction in incidence primarily in less aggressive cancers (i.e., Gleason 5–6) and not in more aggressive cancers (i.e., Gleason 7–10) raises the question of whether this reduction in incidence would lead to any reduction in mortality. This question is presently unanswered.
Men in the finasteride group had statistically significantly more erectile dysfunction, loss of libido, and gynecomastia than men in the placebo group. Men in the finasteride group had a statistically significant incidence of high-grade (Gleason 8–10) cancers during the study.  Subsequent studies showed that diagnostic tests (PSA, prostate digital rectal exam, and prostate biopsy) had improved performance for detection of cancer and of high-grade cancer in men who received finasteride.    Long-term follow-up in the finasteride trial (PCPT) found no increased risk of prostate cancer mortality (HR, finasteride vs. placebo, 0.75; 95% CI, 0.50–1.12).
Overall, 4.3% of men in the dutasteride group compared with 2% of men in the placebo group discontinued the trial because of drug-related adverse events (P < .001). Men in the dutasteride group had a higher incidence of decreased libido, loss of libido, decreased semen volume, erectile dysfunction, and gynecomastia than men in the placebo group. 
The Oncology Drugs Advisory Committee of the FDA examined both finasteride and dutasteride in 2010. Neither agent was recommended for use for chemoprevention of prostate cancer.
The Selenium and Vitamin E Cancer Prevention Trial (SELECT [NCT00006392]) was a large randomized placebo-controlled trial of vitamin E and selenium. It showed no reduction in prostate cancer period prevalence, but an increased risk of prostate cancer with vitamin E alone. 
Carcinoma of the prostate is the most common tumor in men in the United States (other than skin cancer), with an estimated 174,650 new cases and 31,620 deaths expected in 2019.  A wide range of estimates of the impact of the disease are notable. The disease is histologically evident in as many as 34% of men in their fifth decade and in up to 70% of men aged 80 years and older.   Prostate cancer will be diagnosed in almost one-fifth of U.S. men compared with about 3% of men who will be expected to die of the disease.  The estimated reduction in life expectancy of men who die of prostate cancer is approximately 9 years. 
The extraordinarily high rate of clinically occult prostate cancer in the general population compared with the 20-fold lower likelihood of death from the disease indicates that many of these cancers have low biologic risk. Concordant with this observation are the many series of patients with lower-risk (i.e., Gleason 6 and some low-volume Gleason 7 tumors) prostate cancer managed by surveillance alone with high survival rates at 5 and 10 years of follow-up.  Data demonstrate, however, that with longer follow-up, higher-grade cancers are associated with a greater risk of prostate cancer death.  
Because of marked variability in tumor differentiation from one microscopic field to another, many pathologists will report the range of differentiation among the malignant cells that are present in a biopsy using the Gleason grading system. This grading system includes five histologic patterns distinguished by the glandular architecture of the cancer. The architectural patterns are identified and assigned a grade from 1 to 5 with 1 being the most differentiated and 5 being the least differentiated. The sum of the grades of the predominant and next most prevalent will range from 2 (well-differentiated tumors) to 10 (undifferentiated tumors).   Systematic changes to the histological interpretation of biopsy specimens by anatomical pathologists have occurred during the prostate-specific antigen (PSA) screening era (i.e., since about 1985) in the United States.  This phenomenon, sometimes called grade inflation, is the apparent increase in the distribution of high-grade tumors in the population for a period of time but in the absence of a true biological or clinical change. It is possibly the result of an increasing tendency for pathologists to read tumor grade as more aggressive, resulting in a higher preponderance to treat these cancers aggressively.  In general, these changes in interpretation have resulted in almost all prostate cancers being graded with Gleason grades of 3, 4, or 5; Gleason grades of 1 or 2 are highly unusual.
Treatment options available for prostate cancer include radical prostatectomy, external-beam radiation therapy, brachytherapy, cryotherapy, focal ablation, androgen deprivation with luteinizing hormone-releasing hormone analogs and/or antiandrogens, intermittent androgen deprivation, cytotoxic agents, and watchful waiting. Of all the means of management, only radical prostatectomy has been tested in a randomized clinical trial to assess survival benefit. In this study, prostatectomy was found to be superior to surveillance in men with localized prostate cancer, diagnosed in an era before widespread PSA screening. There were reduced rates of prostate cancer mortality (relative risk [RR], 0.56; 95% confidence interval [CI], 0.41–0.77) and overall mortality (RR, 0.71; 95% CI, 0.59–0.86).  Only 12% of the men had nonpalpable T1x tumors, suggesting that a minority of tumors were detected by PSA screening, whereas the majority were clinically detected. The relative efficacy of radical prostatectomy compared with other forms of treatment has not been adequately addressed.  Previous studies that compared radical prostatectomy with radiation therapy and brachytherapy closed because of poor patient accrual. Confounding issues in the treatment of prostate cancer include side effects of treatment, inability to predict the natural history of a given cancer, patient comorbidity that may affect an individual’s likelihood of surviving long enough to be at risk of disease morbidity and mortality, and an increasing body of evidence suggesting that, with careful PSA monitoring following treatment, a substantial fraction of patients may suffer disease recurrence. 
Because of considerable uncertainty regarding the efficacy of treatment and the difficulty with selecting patients for whom there is a known risk of disease progression, opinion in the medical community is divided regarding screening for carcinoma of the prostate. While both digital rectal examination and PSA screening have demonstrated reasonable performance characteristics (sensitivity, specificity, and positive predictive value) for the early detection of prostate cancer, conflicting outcomes of randomized trials examining the impact of screening on mortality has led some organizations to recommend for and others to recommend against screening. 
The tremendous impact of prostate cancer on the U.S. population and the financial burden of the disease for both patients and society have led to an increased interest in primary disease prevention.
The main treatment modalities for prostate cancer are surgery, radiation, hormonal, and active surveillance. For a detailed discussion, refer to the PDQ summary on Prostate Cancer Treatment for more information. The goal of prostate cancer prevention interventions is to reduce the occurrence of prostate cancer, thereby obviating the need for treatment. As the effectiveness of prevention interventions improves, it is expected that the need for treatment will diminish.
Prostate cancer incidence escalates dramatically with increasing age. Although it is a very unusual disease in men younger than 50 years, rates increase exponentially thereafter. The registration rate by age cohort in England and Wales increased from 8 per thousand population in men aged 50 to 56 years to 68 per thousand in men aged 60 to 64 years; 260 per thousand in men aged 70 to 74 years, and peaked at 406 per thousand in men aged 75 to 79 years.  In this same population, the death rate per thousand in 1992 in cohorts of men aged 50 to 54 years, 60 to 64 years, and 70 to 74 years was 4, 37, and 166, respectively.  According to the Surveillance, Epidemiology, and End Results (SEER) Program, incidence of prostate cancer in African Americans exceeds those of whites at all ages. 
Approximately 15% of men with a diagnosis of prostate cancer will be found to have a first-degree relative (e.g., brother, father) with prostate cancer, compared with approximately 8% of the U.S. population.  Approximately 9% of all prostate cancers may result from heritable susceptibility genes.  Several authors have completed segregation analyses, and though a single, rare autosomal gene has been suggested to cause cancer in some of these families, the burden of evidence suggests that the inheritance is considerably more complex.    Evidence from the Prostate Cancer Prevention Trial (PCPT) and Selenium and Vitamin E Cancer Prevention Trial suggest that physician and patient bias lead to a greater likelihood of prostate biopsy, which contributes significantly to the increased risk of prostate cancer diagnosis in men with a family history of the disease. 
The development of the prostate is dependent upon the secretion of dihydrotestosterone (DHT) by the fetal testis. Testosterone causes normal virilization of the Wolffian duct structures and internal genitalia and is acted upon by the enzyme 5-alpha-reductase (5AR) to form DHT. DHT has a 4-fold to 50-fold greater affinity for the androgen receptor than testosterone, and it is DHT that leads to normal prostatic development. Children born with abnormal 5AR (due to a change in a single base pair in exon 5 of the normal type II 5AR gene), are born with ambiguous genitalia (variously described as hypospadias with a blind-ending vagina to a small phallus) but masculinize at puberty because of the surge of testosterone production at that time. Clinical, imaging, and histologic studies of kindreds born with 5AR deficiency have demonstrated a small, pancake-appearing prostate with an undetectable prostate-specific antigen (PSA) level and no evidence of prostatic epithelium.  Long-term follow-up demonstrates that neither benign prostatic hyperplasia (BPH) nor prostate cancer develop.
Other evidence suggesting that the degree of cumulative exposure of the prostate to androgens is related to an increased risk of prostate cancer includes the following:
Ecological studies have found a correlation between serum levels of testosterone, especially DHT, and overall risk of prostate cancer among African American, white, and Japanese males.    However, evidence from prospective studies of the association between serum concentrations of sex hormones, including androgens and estrogens, does not support a direct link.  A collaborative analysis of 18 prospective studies, pooling prediagnostic measures on 3,886 men with incident prostate cancer and 6,438 control subjects, found no association between the risk of prostate cancer and serum concentrations of testosterone, calculated-free testosterone, DHT sulfate, androstenedione, androstanediol glucuronide, estradiol, or calculated-free estradiol.  A caution for interpreting the data is the unknown degree of correlation between serum levels and prostate tissue level. Androstanediol glucuronide may most closely reflect intraprostatic androgen activity, and this measure was not associated with the risk of prostate cancer. This lack of association affirms that risk stratification cannot be made on serum hormone concentrations.
The risk of developing and dying from prostate cancer is dramatically higher among blacks, is of intermediate levels among whites, and is lowest among native Japanese.   Conflicting data have been published regarding the etiology of these outcomes, but some evidence is available that access to health care may play a role in disease outcomes. 
An interesting observation is that although the incidence of latent (occult, histologically evident) prostate cancer is similar throughout the world, clinical prostate cancer varies from country to country by as much as 20-fold.  Previous ecologic studies have demonstrated a direct relationship between a country’s prostate cancer-specific mortality rate and average total calories from fat consumed by the country’s population.   Studies of immigrants from Japan have demonstrated that native Japanese have the lowest risk of clinical prostate cancer, first generation Japanese-Americans have an intermediate risk, and subsequent generations have a risk comparable to the U.S. population.   Animal models of explanted human prostate cancer have demonstrated decreased tumor growth rates in animals who are fed a low-fat diet.   Evidence from many case-control studies has shown an association between dietary fat and prostate cancer risk,    although studies have not uniformly reached this conclusion.    In a review of published studies of the relationship between dietary fat and prostate cancer risk, among descriptive studies, approximately half found an increased risk with increased dietary fat and half found no association.  Among case-control studies, about half of the studies found an increased risk with increasing dietary fat, animal fat, and saturated and monounsaturated fat intake while approximately half found no association. Only in studies of polyunsaturated fat intake were three studies reported of a significant negative association between prostate cancer and fat intake. Fat of animal origin seems to be associated with the highest risk.   In a series of 384 patients with prostate cancer, the risk of cancer progression to an advanced stage was greater in men with a high fat intake.  The announcement in 1996 that cancer mortality rates had fallen in the United States prompted the suggestion that this may be caused by decreases in dietary fat intake during the same time period.  
Two studies were conducted within the PCPT in which prospective nutritional information was collected and all participants were recommended to undergo biopsy. Findings included that, among 9,559 participants there was no association between any supplement or nutrient (including fat) and risk of prostate cancer overall but the risk of high-grade cancer was associated with high intake of polyunsaturated fats. In a subset of 1,658 cases and 1,803 controls, specific fatty acids were examined and docosahexaenoic acid was associated with risk of high-grade disease while trans-fatty acids (TFA) 18:1 and TFA 18:2 were inversely associated with risk of high-grade disease. These large scale studies suggest a complex relationship between nutrients such as fat and risk of prostate cancer.  
The explanation for this possible association between prostate cancer and dietary fat is unknown. Several hypotheses have been advanced, including the following:
A meta-analysis of ten cohort studies (eight from the United States and two from Europe), concluded that men with the highest intake of dairy products (relative risk [RR], 1.11; 95% confidence interval [CI], 1.00–1.22; P = .04) and calcium (RR, 1.39; 95% CI, 1.09–1.77; P = .18) were more likely to develop prostate cancer than men with the lowest intake. The pooled RRs of advanced prostate cancer were 1.33 (95% CI, 1.00–1.78; P = .055) for the highest versus lowest intake categories of dairy products and 1.46 (95% CI, 0.65–3.25; P > .2) for the highest versus lowest intake categories of calcium. High intake of dairy products and calcium may be associated with an increased risk of prostate cancer although the increase may be small. 
Regular multivitamin use has not been associated with the risk of early or localized prostate cancer. However, in this large (295,344 men) study, there was a statistically significantly increased risk of advanced and fatal prostate cancer among men with excessive use of multivitamins. 
The Aspirin/Folate Polyp Prevention Study, a placebo-controlled randomized trial of aspirin and folic acid supplementation for the chemoprevention of colorectal adenomas, was conducted between July 6, 1994, and December 31, 2006. In a secondary analysis, the authors addressed the effect of folic acid supplementation on the risk of prostate cancer. Participants were followed for up to 10.8 (median, 7.0; interquartile range, 6.0–7.8) years and asked periodically to report all illnesses and hospitalizations.  Supplementation with 1 mg of folic acid was associated with an increased risk of prostate cancer. However, dietary and plasma levels among nonmultivitamin users were inversely associated with risk. These findings highlight the potentially complex role of folate in prostate carcinogenesis.  
Cadmium exposure is occupationally associated with nickel-cadmium batteries and cadmium recovery plant smelters and is associated with cigarette smoke.  The earliest studies of this agent documented an apparent association with prostate cancer, but better-designed studies have failed to note an association.  
Dioxin (2,3,7,8 tetrachlorodibenzo-p-dioxin or TCDD) is a contaminant of an herbicide used in Vietnam. This agent is similar to many components of herbicides used in farming. A review of the linkage between dioxin and prostate cancer risk by the National Academy of Sciences Institute of Medicine Committee to Review the Health Effects in Vietnam Veterans of Exposure to Herbicides, found only two articles on prostate cancer with sufficient numbers of cases and follow-up to allow analysis.   The analysis of all available data suggests that the association between dioxin exposure and prostate cancer is not conclusive. 
Several case-control and cohort studies, as well as two meta-analyses, suggested a significant but modest increase in the risk of prostate cancer in men with prostatitis (RR, 1.6) and in those with a history of syphilis or gonorrhea (RR, 1.4).   However, PSA values can be elevated with prostatitis, leading to more prostate biopsies and a greater likelihood of making the diagnosis of cancer. This is an example of ascertainment bias, and this bias can be significant in prostate cancer. Any factor associated with an elevation in serum PSA would be expected to lead to more biopsies being performed, and consequently an artifactual elevation in prostate cancer diagnoses. Despite a significant body of work relating inflammation to cancer, a cause and effect relationship has not been established between prostatitis and prostate cancer.  
The Prostate Cancer Prevention Trial (PCPT), a large randomized placebo-controlled trial of finasteride (an inhibitor of alpha-reductase), was performed in 18,882 men aged 55 years or older. At 7 years, the incidence of prostate cancer was 18.4% in the finasteride group versus 24.4% in the placebo group, a relative risk reduction (RRR) of 24.8% (95% confidence interval [CI], 18.6%–30.6%; P < .001). The finasteride group had more patients with Gleason grade 7 to 10, but the clinical significance of Gleason scoring is uncertain in conditions of androgen deprivation.  High-grade cancers were noted in 6.4% of finasteride patients, compared with 5.1% of men receiving a placebo. The increase in high-grade tumors was seen within 1 year of finasteride exposure and did not increase during this time period. 
Finasteride decreases the risk of prostate cancer but may also alter the detection of disease through effects on prostate-specific antigen (PSA), prostate digital rectal examination (DRE), and decreased prostate volume (24%), creating a detection bias.  Adjustment of PSA in men taking finasteride preserves the performance characteristics for cancer detection. 
Examination of the outcomes of the PCPT found that finasteride significantly reduced the risk of high-grade prostatic intraepithelial neoplasia (HGPIN); HGPIN alone was reduced by 15% (relative risk [RR], 0.85; 95% CI, 0.73–0.99) and HGPIN with prostate cancer was reduced by 31% (RR, 0.69; 95% CI, 0.56–0.85).   The concern that finasteride may increase the risk of high-grade cancer prompted an examination of the rate of cancer development in the PCPT. While a gradual and progressive increase in the number of high-grade tumors would have been expected over the study duration of 7 years, when compared with placebo, this was not the case. The increase in high-grade tumors was seen within 1 year of finasteride exposure and did not increase during this time period.  An analysis of the PCPT data adjusted for the sources of detection bias found that finasteride reduced the incidence of Gleason 5 to 7 and Gleason 3 to 4 prostate cancer, but not Gleason 2 to 3 or Gleason 8 to 10. The reduction in the incidence of Gleason 7 (22%) was less than the reduction in the incidence of Gleason 5 (58%) and Gleason 6 (52%).  An analysis using different methodologies found an overall reduction of both low-grade (Gleason <6) and high-grade (Gleason >7) cancers. 
A follow-up analysis of the PCPT of finasteride mapped study participants with the National Death Index, allowing for an analysis of prostate cancer-specific mortality. With 296,842 person-years of follow-up and a median follow-up of 18.4 years, of the 9,423 men randomly assigned to the finasteride group, there were 3,048 deaths of which 42 were caused by prostate cancer; of the 9,457 men randomly assigned to the placebo group, there were 2,979 deaths of which 56 were caused by prostate cancer. The 25% reduction in risk of prostate cancer death with finasteride was not statistically significant (hazard ratio, finasteride vs. placebo, 0.75; 95% CI, 0.50–1.12). It was concluded that the early concern for an increased risk of high-grade prostate cancer with finasteride was not borne out. In this study, it was notable that, of the 61 prostate cancer deaths for which original Gleason grading was available, 23 (38%) of the prostate cancer deaths were seen in men whose original biopsy Gleason grade was less than or equal to 6. 
A retrospective, population-based, cohort study from the U.S. Department of Veterans Affairs health care system examined the impact of 5-alpha reductase inhibitor (5-ARI) use before prostate cancer diagnosis on prostate cancer-specific mortality.  The authors found that prediagnostic use of 5-ARIs was associated with a delayed diagnosis (median time from first elevated PSA was 3.6 years for men who received 5-ARIs versus 1.4 years for non–5-ARI users) and worsened cancer-specific outcomes (e.g., higher grade, higher clinical stage, more with positive nodes, and higher rates of metastatic disease) in men with prostate cancer. A subsequent letter to the editor pointed out the following challenges with the analysis:
When taken together, these biases call into question the conclusions, which appear to be at odds with the prostate cancer-specific mortality outcomes of the randomized PCPT.
The Reduction by Dutasteride of Prostate Cancer Events trial randomly assigned 8,231 men aged 50 to 75 years at higher risk of prostate cancer (i.e., PSA 2.5–10.0 ng/mL) with one recent negative prostate biopsy to dutasteride at 0.5 mg daily or to placebo. The primary endpoint was prostate cancer diagnosed by prostate biopsy at 2 years and 4 years after randomization. After 4 years, among the 6,729 men (82% of initial population) who had at least one prostate biopsy, 25.1% of the placebo group and 19.9% of the dutasteride group had been diagnosed with prostate cancer, a statistically significant difference (absolute risk reduction, 5.1% and RRR, 22.8% [95% CI, 15.2%–29.8%]). The RRR in years 3 to 4 was similar to the RRR in years 1 to 2. The difference between the groups was entirely due to a reduction in prostate cancers with Gleason score 5 to 7. For years 3 to 4 there was a statistically significant increase in the dutasteride group compared with the placebo group in prostate cancers with Gleason score 8 to 10 (12 cancers in the dutasteride group vs. 1 cancer in the placebo group). 
Overall, there was no statistically significant difference in high-grade tumors for Gleason 8 to 10 cancers in years 1 to 4 (29 tumors in the dutasteride group vs. 19 tumors in the placebo group, 0.9% vs. 0.6%; P = .15). However, in a retrospective analysis there was a statistically significant difference between years 3 to 4. Because this is a small retrospective subgroup, the finding of an increase in Gleason 8 to 10 cancers is of uncertain validity. However, the finding of no reduction in these cancers is more significant. 
While long-term data are unavailable for dutasteride as a cancer prevention agent, evidence is now available that finasteride does not have a significant effect on overall survival or prostate cancer-specific survival. Its effect is primarily in preventing the diagnosis of prostate cancer and the subsequent events (staging, treatment, follow-up, and management of treatment-related side effects) after diagnosis.
Agents that are used for hormonal therapy of existing prostate cancers would be unsuitable for prostate cancer chemoprevention because of the cost and wide variety of side effects including sexual dysfunction, osteoporosis, and vasomotor symptoms (hot flushes).  Newer antiandrogens may play a role as preventive agents in the future. 
A Cochrane systematic review of all published studies of clinical outcome investigations of the prostate preventive effects of 5-ARIs through 2010 that were at least one year in duration concluded that finasteride and dutasteride reduce the risk of being diagnosed with prostate cancer among men who are screened regularly for prostate cancer. The review also concluded that mortality effects could not be assessed from these studies and that persistent use of these agents increased sexual and erectile dysfunction. The review was based on MEDLINE and Cochrane Collaboration Library computerized searches through June 2010 using the Medical Subject Headings terms and text words finasteride, dutasteride, neoplasms, azasteroids, reductase inhibitors, and enzyme inhibitors to identify randomized trials. Eight studies met the inclusion criteria. Only the PCPT and the Reduction by Dutasteride of Prostate Cancer Events study were designed to assess the impact of 5-ARIs on prostate cancer period prevalence. Reviews of all eight studies concluded that compared with placebo, 5-ARIs resulted in 25% RR reduction in prostate cancers detected for cause (RR, 0.75; 95% CI, 0.67–0.83 and 1.4% absolute risk reduction [3.5% vs. 4.9%]). Six trials of 5-ARIs versus placebo assessed prostate cancers detected overall. Among these there was a 26% RR reduction favoring 5-ARIs (RR, 0.74; 95% CI, 0.55–1.00 and 2.9% absolute risk reduction [6.3% vs. 9.2%]). There were reductions across age, race, and family history. One placebo-controlled trial of men considered at greater risk for prostate cancer based on age, elevated PSA, and previous suspicion of prostate cancer leading to a prostate biopsy reported that dutasteride did not reduce prostate cancers detected for cause based on needle biopsy but did reduce risk of overall incident prostate cancer detected by biopsy by 23% (RR, 0.77; 95% CI, 0.7–0.85 and absolute risk reduction, 16.1% vs. 20.8%). There were reductions across age, family history of prostate cancer, PSA level, and prostate volume subgroups. The Cochrane review defined for cause cancers as follows:
Results from studies of the association between dietary intake of fruits and vegetables and risk of prostate cancer are not consistent. A study evaluated 1,619 prostate cancer cases and 1,618 controls in a multicenter, multiethnic population. The study found that intake of legumes and yellow-orange and cruciferous vegetables was associated with a lower risk of prostate cancer.
The European Prospective Investigation into Cancer and Nutrition examined the association between fruit and vegetable intake and subsequent prostate cancer. After an average follow-up of 4.8 years, 1,104 men developed prostate cancer among the 130,544 male participants. No statistically significant associations were observed for fruit intake, vegetable intake, cruciferous vegetable intake, or the intake of fruits and vegetables combined. 
One study of dietary intervention over a 4-year period with reduced fat and increased consumption of fruit, vegetables, and fiber had no impact on serum PSA levels.  It is unknown whether dietary modification through the use of a low-fat, plant-based diet will reduce prostate cancer risk. While this outcome is unknown, multiple additional benefits may be gleaned by such a diet, including a lower risk of hyperlipidemia, better control of blood pressure, and a lower risk of cardiovascular disease—all of which may merit adoption of such a diet.
While several agents, including alpha-tocopherol, selenium, lycopene, difluoromethylornithine,      vitamin D,    and isoflavonoids,   have shown potential in either clinical or laboratory studies for chemoprevention of prostate cancer, the correlations of cancer prevention with these agents are increasingly of concern given the statistically significant increased risk of prostate cancer with alpha-tocopherol in the Selenium and Vitamin E Cancer Prevention Trial (SELECT) and the lack of preventive effect (actually, a nonsignificant increase in prostate cancer risk) with selenium.
The SELECT (NCT00006392) was a large randomized placebo-controlled trial of vitamin E and selenium. It showed no reduction in prostate cancer period prevalence, but an increased risk of prostate cancer with vitamin E alone. 
Compared with the placebo group in which 529 men developed prostate cancer, there was a statistically significant increase in prostate cancer in the vitamin E group (620 cases), but not in the selenium plus vitamin E group (555 cases) or in the selenium group (575 cases). The magnitude of increase in prostate cancer risk with vitamin E alone was 17%. Of interest, the statistically increased risk of prostate cancer among men receiving vitamin E was seen after study supplements had been discontinued suggesting a longer-term effect of this agent. 
Evidence exists that a diet with a high intake of fruits and vegetables is associated with a lower risk of cancer. Which, if any, micronutrients may account for this reduction is unknown. One group of nutrients often postulated as having chemoprevention properties is the carotenoids. Lycopene is the predominant circulating carotenoid in Americans and has a number of potential activities, including an antioxidant effect.  It is encountered in a number of vegetables, most notably tomatoes, and is best absorbed if these products are cooked and in the presence of dietary fats or oils.
The earliest studies of the association of lycopene and prostate cancer risk were generally negative before 1995 with only one study of 180 case-control patients showing a reduced risk.     In 1995, an analysis of the Physicians’ Health Study found a one-third reduction in prostate cancer risk in the group of men with the highest consumption of tomato products when compared with the group with the lowest level of consumption, which was attributed to the lycopene content of these vegetables.  This large analysis prompted several subsequent studies, the results of which were mixed.   A review of the published data concluded that the evidence is weak that lycopene is associated with a reduced risk because previous studies were not controlled for total vegetable intake (i.e., separating the effect of tomatoes from vegetables), dietary intake instruments are poorly able to quantify lycopene intake, and other potential biases.  Specific dietary supplementation with lycopene remains to be demonstrated to reduce prostate cancer risk. In the largest prospective study to date, the PCPT, lycopene was not associated with any reduction in risk of prostate cancer among 9,559 men studied. Similarly, there was no relationship between lycopene serum concentrations and risk of prostate cancer.  
The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.
Added text to state that the main treatment modalities for prostate cancer are surgery, radiation, hormonal, and active surveillance; the goal of prostate cancer prevention interventions is to reduce the occurrence of prostate cancer, thereby obviating the need for treatment. As the effectiveness of prevention interventions improves, it is expected that the need for treatment will diminish.
Added text about a retrospective, population-based, cohort study from the U.S. Department of Veterans Affairs health care system that examined the impact of 5-alpha reductase inhibitor (5-ARI) use before prostate cancer diagnosis on prostate cancer-specific mortality (cited Sarkar et al. as reference 9); the authors found that prediagnostic use of 5-ARIs was associated with a delayed diagnosis and worsened cancer-specific outcomes in men with prostate cancer, however, a subsequent letter to the editor pointed out several challenges with the analysis.
Added text to state that when taken together, these biases call into question the conclusions, which appear to be at odds with the prostate cancer-specific mortality outcomes of the randomized Prostate Cancer Prevention Trial.
This summary is written and maintained by the PDQ Screening and Prevention Editorial Board, which is editorially independent of NCI. The summary reflects an independent review of the literature and does not represent a policy statement of NCI or NIH. More information about summary policies and the role of the PDQ Editorial Boards in maintaining the PDQ summaries can be found on the About This PDQ Summary and PDQ® - NCI's Comprehensive Cancer Database pages.
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about prostate cancer prevention. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.
This summary is reviewed regularly and updated as necessary by the PDQ Screening and Prevention Editorial Board, which is editorially independent of the National Cancer Institute (NCI). The summary reflects an independent review of the literature and does not represent a policy statement of NCI or the National Institutes of Health (NIH).
Board members review recently published articles each month to determine whether an article should:
Changes to the summaries are made through a consensus process in which Board members evaluate the strength of the evidence in the published articles and determine how the article should be included in the summary.
Any comments or questions about the summary content should be submitted to Cancer.gov through the NCI website's Email Us. Do not contact the individual Board Members with questions or comments about the summaries. Board members will not respond to individual inquiries.
Some of the reference citations in this summary are accompanied by a level-of-evidence designation. These designations are intended to help readers assess the strength of the evidence supporting the use of specific interventions or approaches. The PDQ Screening and Prevention Editorial Board uses a formal evidence ranking system in developing its level-of-evidence designations.
PDQ is a registered trademark. Although the content of PDQ documents can be used freely as text, it cannot be identified as an NCI PDQ cancer information summary unless it is presented in its entirety and is regularly updated. However, an author would be permitted to write a sentence such as “NCI’s PDQ cancer information summary about breast cancer prevention states the risks succinctly: [include excerpt from the summary].”
The preferred citation for this PDQ summary is:
PDQ® Screening and Prevention Editorial Board. PDQ Prostate Cancer Prevention. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: https://www.cancer.gov/types/prostate/hp/prostate-prevention-pdq. Accessed <MM/DD/YYYY>. [PMID: 26389405]
Images in this summary are used with permission of the author(s), artist, and/or publisher for use within the PDQ summaries only. Permission to use images outside the context of PDQ information must be obtained from the owner(s) and cannot be granted by the National Cancer Institute. Information about using the illustrations in this summary, along with many other cancer-related images, is available in Visuals Online, a collection of over 2,000 scientific images.
The information in these summaries should not be used as a basis for insurance reimbursement determinations. More information on insurance coverage is available on Cancer.gov on the Managing Cancer Care page.
More information about contacting us or receiving help with the Cancer.gov website can be found on our Contact Us for Help page. Questions can also be submitted to Cancer.gov through the website’s Email Us.