Vitamin E and Selenium Do Not Prevent Prostate Cancer; Use of the Supplements Stopped in Large-Scale Study

October 29, 2008 — The SELECT (Selenium and Vitamin E Cancer Prevention Trial) prostate cancer prevention study is instructing its 35,000-plus participants to stop taking the 2 nutritional supplements because of an apparent lack of benefit and a possibility of harm.

“The Data and Safety Monitoring Committee made the decision to stop use of the supplements, not to stop the trial. We will follow participants for 3 more years to determine if there is any benefit or any harm,” said Larry Baker, MD, chairman of the Southwest Oncology Group, which coordinated the trial, and professor of medicine at University of Michigan Medical School in Ann Arbor.

The Data and Safety Monitoring Committee said that “the data could not exclude a small chance that the study supplements might have effects later in the men’s lives.” However, the antioxidants selenium and vitamin E, taken alone or together for an average of 5 years, did not prevent prostate cancer, according to the committee.

The antioxidants selenium and vitamin E, taken alone or together for an average of 5 years, did not prevent prostate cancer.

“We went back to the biologists, and they said that 8 months was sufficient exposure to see benefit,” Dr. Baker explained.

The data from SELECT also show 2 trends that were of concern but not statistically significant: in men taking only vitamin E, there were slightly more cases of prostate cancer; and, in men taking only selenium, there were slightly more cases of diabetes. Neither of these findings means an increased risk from the supplements, and they could be due to chance, according to the National Cancer Institute (NCI), which funded the trial.

The Data and Safety Monitoring Committee also determined that it was unlikely that selenium and vitamin E supplementation would ever produce a 25% reduction in prostate cancer, which was the study’s goal.

Dr. Baker said that the results to date speak for themselves, and that SELECT is a much larger trial than previous trials that suggested benefit. “This is the definitive study and anyone who argues that is ignoring the facts.”

Source:

1. Vitamin E and Selenium Do Not Prevent Prostate Cancer; Use of the Supplements Stopped in Large-Scale Study