|Review of Prostate Cancer Prevention Study
Shows No Benefit for Use of Selenium and Vitamin E Supplements
Initial, independent review of study data from the Selenium and
Vitamin E Cancer Prevention Trial (SELECT), funded by the National
Cancer Institute (NCI) and other institutes that comprise the National
Institutes of Health shows that selenium and vitamin E supplements,
taken either alone or together, did not prevent prostate cancer.
The data also showed two concerning trends: a small but not statistically
significant increase in the number of prostate cancer cases among
the over 35,000 men age 50 and older in the trial taking only vitamin
E and a small, but not statistically significant increase in the
number of cases of adult onset diabetes in men taking only selenium.
Because this is an early analysis of the data from the study, neither
of these findings proves an increased risk from the supplements
and both may be due to chance.
The Southwest Oncology Group (SWOG), an international network of
research institutions, coordinates SELECT at more than 400 clinical
sites in the United States, Puerto Rico, and Canada.
SELECT participants are receiving letters explaining the study
review and telling them to stop taking their study supplements.
Participants will continue to have their health monitored by study
staff, which may include regular digital rectal exams and PSA (prostate-specific
antigen) tests to detect prostate cancer. Investigators intend
to follow the participants for about three years to determine the
long-term effects of having taken either supplement or placebo
and to complete a biorepository of blood samples that will be used
in extensive molecular analyses to give researchers a better understanding
of prostate cancer, other cancers, and other diseases of male aging.
This additional data collection is a vital part of the study.
Neither the men nor their physicians know which supplements or
placebos the men have been taking, a procedure known as blinding
or masking. As followup of the SELECT participants continues, the
participants will continue to be blinded. A blinded followup may
avoid unintentional bias and potentially false conclusions. However,
at the request of a participant, they will be informed which supplement,
if any, they received.
"SELECT was always designed as a study that would answer more
than a single question about prostate cancer," said Eric Klein,
M.D., a study co-chair for SELECT, and a physician at the Cleveland
Clinic. "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."
SELECT was undertaken to substantiate earlier, separate findings
from studies in which prostate cancer was not the primary outcome:
a 1998 study of 29,133 male smokers in Finland who took vitamin
E to prevent lung cancer surprisingly showed 32 percent fewer prostate
cancers in men who took the supplement, and 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 percent
fewer prostate cancers than men who did not take the supplement.
Based on these and other earlier findings, in 2001, men were recruited
to participate in SELECT. They were randomly assigned to take one
of four sets of supplements or placebos, with more than 8,000 men
in each group. One group took both selenium and vitamin E; one
took selenium and a vitamin E placebo; one took vitamin E and a
selenium placebo; and the final group received placebos of both
It should be noted that in 2003, while SELECT was recruiting men,
a different SWOG-sponsored study reported that the drug finasteride
reduced the incidence of prostate cancer by 25 percent. When this
was discovered, men on SELECT were informed and allowed to take
finasteride. Finasteride has not yet been approved by the U.S.
Food and Drug Administration for prostate cancer prevention.
Except for skin cancer, prostate cancer is the most common type
of cancer in men in the United States. In 2008, there will be an
estimated 186,320 new cases of prostate cancer and 28,660 deaths
from this disease in the United States. "Finding methods to prevent
and treat prostate cancer remains a priority for the NCI, and with
the aid of new molecular diagnostic tools and applications, we
hope to continue to make headway in reducing deaths and new cases
of this disease," said NCI director John E. Niederhuber, M.D. "The
science of cancer prevention is also leading toward individualized,
molecular prevention, in which we will calculate risk and design
preventive steps based on an individual's genome."
SELECT has been funded by NCI for $114 million, with additional
monies from the National Center for Complementary and Alternative
Medicine, and with substudies funded and conducted by the National
Heart, Lung and Blood Institute, the National Institute of Aging
and the National Eye Institute at NIH. The substudies were evaluating
the effects of selenium and vitamin E on chronic obstructive pulmonary
disease, the development of Alzheimer's disease, and the development
of macular degeneration and cataracts, and will continue without
participants taking study supplements. An NCI-funded substudy is
looking at the effects of the supplements on men who developed
"The SELECT trial owes a tremendous debt to our volunteers, the
thousands of men who offered their time and enthusiastic participation,
all in the interest of a future when prostate cancer can be prevented," said
Laurence H. Baker, D.O., chairman of the Southwest Oncology Group.
SELECT investigators are analyzing the data and will submit the
analysis for publication in a peer-reviewed medical journal.
For a Q&A on SELECT, please go to http://www.cancer.gov/newscenter/pressreleases/SELECTQandA.
The Southwest Oncology Group (www.swog.org)
is one of the largest cancer clinical trials cooperative groups
in the United States. Funded by research grants from the National
Cancer Institute, part of the National Institutes of Health, the
group conducts clinical trials to prevent and treat cancer in adults,
and to improve the quality of life for cancer survivors. The group's
network of more than 5,000 physician-researchers practice at nearly
550 institutions, including 18 NCI-designated cancer centers. Headquartered
in Ann Arbor, Mich. (734-998-7130), the group has an operations
office in San Antonio, Tex., and a statistical center in Seattle,
The National Center for Complementary and Alternative Medicine's mission is to explore complementary and alternative medical practices in the context of rigorous science, train CAM researchers, and disseminate authoritative information to the public and professionals. For additional information, call NCCAM's Clearinghouse toll free at 1-888-644-6226, or visit the NCCAM Web site at nccam.nih.gov.
NCI leads the National Cancer Program and the NIH effort to dramatically
reduce the burden of cancer and improve the lives of cancer patients
and their families, through research into prevention and cancer
biology, the development of new interventions, and the training
and mentoring of new researchers. For more information about cancer,
please visit the NCI Web site at http://www.cancer.gov or
call NCI's Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and Centers
and is a component of the U.S. Department of Health and Human Services.
It is the primary federal agency for conducting and supporting basic,
clinical and translational medical research, and it investigates
the causes, treatments, and cures for both common and rare diseases.
For more information about NIH and its programs, visit www.nih.gov.