SELECT study halted

Participants to stop taking supplements; follow-up will continue.

The National Cancer Institute announced on Monday that the multinational Selenium and Vitamin E Cancer Prevention Trial, or SELECT, would be halted after an early analysis has shown that selenium and vitamin E supplements, taken either together or alone, did not have any benefit in the treatment of prostate cancer.

An initial independent review of study data indicated two small but not statistically significant trends: an increase in the number of prostate cancer cases in men taking only vitamin E and an increase in the number of cases of adult onset diabetes in men taking only selenium.

Because the data are from an early analysis, neither of these findings proves an increased risk from the supplements and both may be due to chance, according to an NCI press release.

SELECT has enrolled over 35,000 men since it began in 2001. Men were randomly assigned to either selenium and vitamin E supplements, selenium and a vitamin E placebo, vitamin E and a selenium placebo, or two placebos. Participants in the study are receiving letters to explain the study review and instructing them to stop taking their study supplements.

Follow-up of participants will continue for about three years, which may include digital rectal exams and PSA tests to detect prostate cancer. Participants and physicians will remain blinded to supplement assignment to avoid unintentional bias and potentially false conclusions.

SELECT was undertaken to substantiate earlier findings from studies in which prostate cancer was not the primary outcome. A 1998 study of 29,133 male smokers in Finland found that men who took vitamin E to prevent lung cancer had 32% fewer prostate cancers. A 1996 study of 1,312 men and women with skin cancer who took selenium for prevention of the disease showed that men who took the supplement had 52% fewer prostate cancers than men who did not take the supplement. – by Leah Lawrence

The recent information regarding SELECT is an important and powerful reminder of the necessity for careful, well-designed clinical trials. There are many instances in the practice of medicine where there are persuasive inferential data that physicians or patients ‘should do such and such.’ Although physicians must make decisions on a daily basis as to the manner in which we incorporate these ‘truisms’ into our practices, these findings from SELECT emphasize that what ‘should be’ true isn't always true. SELECT results provide very persuasive data that supplements of vitamin E and selenium do not reduce the risk of prostate cancer. Without this well-designed trial we would never have had strong scientific data on this issue — and many would continue to recommend the use of selenium and vitamin E. These data should influence what we tell our patients and their family members: Selenium/vitamin E provide no benefit in prostate cancer-risk reduction and there is the possibility that they may do harm.

– Donald Trump, MD

HemOnc Today Editorial Board member