Oct. 28, 2008 -- The National Cancer Institute has halted its $114 million
study of whether vitamin E and selenium can prevent prostate cancer.
They can't -- at least not in the formulations and dosages used in the
study, called SELECT (SELenium and vitamin ECancer
prevention Trial). The safety
panel for the 35,000-man study called for a halt when an early look at the data
showed no benefit for the treatment.
There were slightly more prostate cancers in men taking
vitamin E alone, and slightly more diabetes in men taking only
selenium. But neither finding was statistically significant, meaning they were
likely due to chance.
"The data to date suggest, but do not prove, that vitamin E may slightly
increase the chance of getting prostate cancer, and that selenium may increase
the chance of getting diabetes mellitus," warns a letter sent to study
participants by the Southwest Oncology Group, which ran the NCI-funded
Study participants were told to stop taking the two pills they'd been taking
every day since the trial opened in 2001. The men received either vitamin E
(400 milligrams) and selenium (200 micrograms), vitamin E and placebo, selenium
and placebo, or placebos alone.
The men can now ask to be told which treatment they received. And because
the study was designed to look at more than just prostate cancer (it received
an additional $16.5 million from various NIH agencies), study participants will
continue to receive regular checkups.
"SELECT was always designed as a study that would answer more than a
single question about prostate cancer," Cleveland Clinic researcher and
study co-chair Eric Klein, MD, says in a news release. "As we continue to
monitor the health of these 35,000 men, this information may help us understand
why two nutrients that showed strong initial evidence to be able to prevent
prostate cancer did not do so."
That evidence included a 1998 Finnish study of whether vitamin E could
prevent lung cancer in some 30,000
smokers. It didn't, but men taking vitamin E had 32% fewer prostate