Methods to integrate other risk factors associated with prostate cancer into individualized risk prediction are needed. We included men from the placebo group of the PCPT who underwent prostate biopsy, had at least one PSA measurement and a digital rectal examination DRE performed during the year before the biopsy, and had at least two PSA measurements performed during the 3 years before the prostate biopsy.
Logistic regression was used to model the risk of prostate cancer and high-grade disease associated with age at biopsy, race, family history of prostate cancer, PSA level, PSA velocity, DRE result, and previous prostate biopsy.
The authors examined nutritional risk factors for prostate cancer among 9, participants in the Prostate Cancer Prevention Trial United States and Canada, The presence or absence of cancer was determined by prostate biopsy, which was recommended during the trial because of an elevated prostate-specific antigen level or an abnormal digital rectal examination and was offered to all men at the trial's end.
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NCI Grant Policies. Legal Requirements. The study was conducted in a well-nourished population and, thus, these results may not preclude potential benefits in less well-nourished populations. One concern is the choice of dose used. It is not feasible to test multiple doses in these large-scale trials. The doses of vitamin E and C in the PHS were chosen because they were in the range of those commonly in use, did not have known major side effects that would impact adherence and because their safety data were sound — a critical issue when conducting a trial by mail.
Gamma-tocopherol has been postulated to possibly play a more important role in prostate cancer protection. We had to balance the desire to extend treatment and follow-up as long as possible considering issues of cost and compliance; however, it remains possible that chemoprevention may require even longer durations of treatment and follow-up than is feasible in randomized trials.
Compliance remains an issue of concern in any long-term study, but levels of compliance in the PHS II remained good after a mean follow-up of 8 years. It remains possible that these agents have a role in chemoprevention only when taken in the context of other micronutrients, a hypothesis we are testing in the continuation of the multivitamin component of PHS II. In this long-term, large-scale, low-cost trial, after a mean of 8 years of treatment and follow-up in 14, men, neither vitamin E nor vitamin C supplementation reduced the risk of prostate or total cancer.
There was also no clear effect of either agent on other site-specific cancers. It is reassuring that there was not a clear signal of harm for either agent. These data provide no support for the use of these supplements in the prevention of cancer in middle-aged and older men. Financial Disclosures: Dr Gaziano reported receiving investigator-initiated research funding from the National Institutes of Health, the Veterans Administration, Veroscience and Amgen; serving as a consultant or receiving honoraria from Bayer AG and Pfizer; and serving as an expert witness for Merck.
No other authors reported financial disclosures. Dr Manson reported receiving investigator-initiated research funding from the National Institutes of Health and assistance with study pills and packaging from BASF and Cognis. Role of the Sponsors: BASF, Wyeth Pharmaceuticals, and DSM Nutritional Products Inc had no role in the study design; conduct of the study; collection, management, analysis, and interpretation of the data; or preparation, review, or approval of the manuscript.
Disclaimer: Dr Gaziano, a contributing editor for JAMA , was not involved in the editorial review of or decision to publish this article. Additional Contributions: We are indebted to the 14 physician participants for their long-standing dedication and conscientious collaboration.
National Center for Biotechnology Information , U. Author manuscript; available in PMC Jan 7. Glynn , ScD, William G. Sesso , ScD, and Julie E. Buring , ScD. Author information Copyright and License information Disclaimer. Address for correspondence: J.
Author Contributions: The co-authors had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analyses. Gaziano and Dr. Glynn contributed equally and are co—first authors of this article. Copyright notice. The publisher's final edited version of this article is available at JAMA. See other articles in PMC that cite the published article. Abstract Context Many Americans take vitamins in the hopes of preventing chronic diseases such as cancer, and vitamins E and C are among the most common individual supplements.
Objective To evaluate whether long-term vitamin E or C supplementation decreases risk of prostate and total cancer events among men. Intervention Individual supplements of IU of vitamin E every other day and mg vitamin C daily. Main Outcome Measures Prostate and total cancer.
Results During a mean follow-up of 8. Conclusions In this large long-term trial of male physicians, neither vitamin E nor C supplementation reduced the risk of prostate or total cancer. Keywords: vitamin E, vitamin C, prostate cancer, total cancer, randomized clinical trial, men. Open in a separate window. Figure 1. Study Treatment, Follow-up, and Compliance Participants were sent monthly calendar packs, containing vitamin E or placebo taken every other day , and vitamin C or placebo taken daily , every six months for the first year and annually thereafter.
Confirmation of End Points For the vitamin E component, the primary cancer endpoint was total prostate cancer; total cancer excluding non-melanoma skin cancer was the primary endpoint for the vitamin C component and a pre-specified secondary endpoint for vitamin E. Statistical Analyses All primary analyses classified subjects based upon the intention-to-treat principle, in which randomized participants were classified according to their randomized vitamin E or vitamin C treatment assignments and were followed up until the occurrence of a disease end point, death, loss to follow-up, or the end of the vitamin E and vitamin C components of PHS II on August 31, , whichever came first.
Self-reported baseline characteristics No. Abbreviations: SD, standard deviation. The numbers do not always sum to group totals due to missing information for some variables. Vitamin E and Cancer The overall rates of prostate cancer were 9. Figure 2. Vitamin E Vitamin C No. Abbreviations: CI, confidence interval; HR, hazard ratio. For the incidence of site-specific cancers, analyses were restricted to men without that site-specific cancer at baseline.
Vitamin E No. Vitamin C and Cancer The overall rates of total cancer for the active and placebo vitamin C groups were Figure 3. Adverse Effects As previously published, 20 we assessed a number of potential side effects of vitamins E and C, and there were no significant effects of either agent on minor bleeding including hematuria, easy bruising, and epistaxis or gastrointestinal tract symptoms peptic ulcer, constipation, diarrhea, gastritis, and nausea , fatigue, drowsiness, skin discoloration or rashes, and migraine.
COMMENT In this large-scale, randomized controlled trial among middle-aged and older men, neither long-term vitamin E nor vitamin C supplementation reduced the risk of prostate or total cancer. Vitamin C and Cancer In contrast to vitamin E, which is available in a limited number of foods, vitamin C is derived from many fruit and vegetable sources.
Strengths and Limitations Major strengths of this study were the high levels of adherence to the study agents over a long period of time and the high quality of reporting of health information.
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