The selenium and vitamin E cancer prevention trial (SELECT)

Largest-ever prostate cancer prevention trial opens
32,000 men sought to test vitamin E and selenium

Healthy men age 55 and older are needed for the largest-ever prostate cancer prevention study, launched today by the National Cancer Institute (NCI) and a network of researchers known as the Southwest Oncology Group (SWOG). The selenium and vitamin E cancer prevention Trial, or SELECT, will determine if these two dietary supplements can protect against prostate cancer, the most common form of cancer, after skin cancer, in men. The study will include a total of 32,400 men.

More than 400 sites in the United States, Puerto Rico, and Canada are recruiting participants for SELECT, which will take up to 12 years to complete. SELECT is the first study designed to look specifically at the effects of vitamin E and selenium, both separately and together, in preventing prostate cancer.

“We are looking for quite a few good men to join SELECT because it is an incredibly important prostate cancer prevention study,” said Charles A. Coltman, Jr., M.D., chairman of SWOG and director of the San Antonio Cancer Institute in Texas. “Previous research with vitamin E and selenium—in studies focused on other kinds of cancer—suggested that these nutrients might prevent prostate cancer. SELECT is focused on prostate cancer and, when the study is finished, we will know for sure whether these supplements can prevent the disease.”

During this year alone, prostate cancer will be diagnosed in about 198,100 Americans and more than 31,500 men are expected to die of the disease. Risk factors for the disease include being over age 55, being black, or having a father or brother with prostate cancer.

“It is crucial that men of all races and ethnic backgrounds participate in SELECT,” said Leslie Ford, M.D., associate director for clinical research in NCI’s Division of Cancer Prevention. “And since African-American men have the highest incidence of prostate cancer in the world, we especially encourage them to consider joining this trial.” The disease also strikes black men at a younger age, so they will be eligible to enroll in the study at age 50, vs. age 55 for other racial and ethnic groups. There is no upper age limit for participation in SELECT.

“The men who join SELECT not only have a chance to prevent prostate cancer for themselves, but they also may help their sons and grandsons live free from the disease,” said Ford.

Selenium and vitamin E, both naturally occurring nutrients, are antioxidants. They are capable of neutralizing toxins known as “free radicals” that might otherwise damage the genetic material of cells and possibly lead to cancer. These nutrients were chosen for study because of the results of two other large cancer prevention trials.

In a 1996 reported study of selenium to prevent nonmelanoma skin cancer in 1,000 men and women, investigators found that while the supplement did not reduce skin cancer, it did decrease the incidence of prostate cancer in men by more than 60 percent.

Another trial, published in 1998**, in which beta carotene and vitamin E were tested to prevent lung cancer in 29,000 Finnish men who smoked, those who took vitamin E had 32 percent less prostate cancer. Neither beta carotene nor vitamin E prevented lung cancer. In fact, the men who smoked and took beta carotene were more apt to get lung cancer and die from it than men who didn’t take this supplement.

“SELECT is the critical next step for pursuing the promising leads we saw for the prevention of prostate cancer,” said Ford, who is responsible for all aspects of NCI’s involvement in SELECT. “The only way to determine the real value of these supplements for prostate cancer is to do a large clinical trial focused specifically on this disease.” Study investigators hope to recruit all the study participants during the first five years of the trial, so that each man can be followed for at least seven years.

Men in the study will visit their study site once every six months. Upon enrollment, they will be assigned by chance to one of four groups. One group will take 200 micrograms of selenium daily plus an inactive capsule, or placebo, that looks like vitamin E. Another group will take 400 milligrams of vitamin E daily along with a placebo that looks like selenium. A third group will take both selenium and vitamin E. And a final group will be given two placebos.

Men who join SELECT will not need to change their diet in any way, but they must stop taking any supplements they buy themselves that contain selenium or vitamin E. If participants wish to take a multivitamin, SWOG will provide without charge, a specially formulated one that does not contain selenium or vitamin E.

Men may be able to participate in SELECT if they:

  • Are age 55 or older; age 50 or older for black men
  • Have never had prostate cancer and have not had any other cancer, except nonmelanoma skin cancer, in the last five years
  • Are generally in good health