The rationale of the trial was solid. There is evidence that anti-oxidants (such as Vitamin E) help to reduce the risk of certain cancers. Vitamin E and Selenium have both been shown in earlier studies to suggest a decrease in the risk of prostate cancer and thus were chosen to be tested in a population-based randomized trial involving over 35,000 men in the U.S. and Canada (there were 15- 20 Canadian sites). The study was terminated early because of the concern that oral supplementation with vitamin E increased the risk of prostate cancer in healthy men which was confirmed in a subsequent report of longer participant follow-up. This information from a well-designed and well-conducted study is sending out several important messages.
1. This study was based on a hypothesis. To support or refute the hypothesis is precisely the reason why clinical trials are needed and why volunteer subjects are required to carefully evaluate any indications or claims of beneficial effects from certain drugs or treatments.
2. The results of the clinical trial may or may not confirm the results of preliminary trials and as such researchers and subjects/patients need to recognize this when participating in a clinical trial.
3. Unquestioned premature adoption of a novel treatment based on unsubstantiated claims may be harmful.
4. Contrary to popular belief, vitamins and “natural substances” may be harmful and do exactly the opposite to what is expected regardless as to whether they are consumed under medical supervision or not.
5. The benefits of a substance are often dose related and may be harmful when taken at a higher dose. In the SELECT trial, the daily dose (400 IU or 267 mg) of Vitamin E supplement was several times higher than what had been suggested by previous trials to be beneficial.
Researchers are also pointing out there are many other factors which interact with and influence the effects of any given treatment on different individuals, resulting in different outcomes. For instance, the effects of vitamin E on individuals may depend on their genetic makeup and whether they smoke or not.
Many valuable lessons (see above) can be learned from the SELECT trial. The most important message from this trial is that we need to continue doing well designed, randomized, controlled clinical trials, to test and validate new ideas and discoveries in the ongoing quest for new approaches to the prevention and management of prostate cancer.
Additional Information pertaining to vitamin E and prostate cancer: In the SELECT trial, the men taking high doses of Vitamin E were at a higher risk of prostate cancer. In the group of men who took only the placebo pills, after seven years, 65 prostate cancer cases were diagnosed for every 1,000 men. For the men who took Vitamin E only, for every 1,000 men, there were 76 cases of prostate cancer diagnosed (11 additional cases of prostate cancer for every 1,000 men over seven years). In other words, if 1,000 healthy men not taking Vitamin E similar to those in the SELECT study were followed with annual physician visits, 65 of them would be expected to be diagnosed with prostate cancer over a seven year period. If these same men took 400 I.U. Vitamin E daily for 5.5 years, 76 of the 1000 would be expected to be diagnosed with prostate cancer over a seven year period (i.e., 11 additional cases over seven years). Based on the results of the SELECT trial, men taking high doses of vitamin E supplements should speak with their doctor about the risks and benefits of vitamin E intake and also initiate monitoring for possible prostate cancer. The dose used in the SELECT trial was 400 I.U. (International Units) (equivalent to 267 mg of alpha-tocopherol). The recommended dietary allowance (RDA) by the Food and Nutrition Board at the Institute of Medicine of the U.S. National Academies is only 15 mg of alpha-tocopherol. The average dietary intakes of vitamin E among healthy adults are probably higher than the RDA and thus supplementation is generally not necessary. A dose much higher than the RDA may in fact be harmful.
Dr. Joseph Chin, O.Ont., M.D., FRCSC Executive Member, Sceintific and Medical Advisory Committee Chair, Patient & Public Education Committee, Prostate Cancer Canada Dr.Chin is Professor and Chair of the Division of Surgical Oncology and Head of the Provincial Surgical Oncology Program for the Southwestern Ontario Region. His clinical practice at London Health Sciences Centre,Victoria Hospital, is concentrated in Urologic Oncology. Dr. Chin has received many research grants from international and national granting agencies. His laboratory and clinical research interests are in prostate cancer management, including minimally invasive and alternative forms of management. He has been a Canadian pioneer in such procedures as robotic assisted laparoscopic prostatectomy and cryosurgery for prostate cancer. Dr. Chin has published well over 100 research papers and book chapters, mostly in the area of uro-oncology. Dr. Chin has co-authored a book with a prostate cancer survivor entitled "PROSTATE! PROSTATE! PROSTATE" detailing information that is essential for prostate cancer patients and their family members. Dr. Chin was bestowed with the high honour of being appointed to the Order of Ontario in 2011.