Selenium and Vitamin E Cancer Prevention, Part 2

by National Cancer Institute

(Page 2 of 2)

8. What tests were used to determine eligibility for SELECT?

Tests included a digital rectal examination (DRE) and a prostate-specific antigen (PSA) test. During a DRE, a doctor inserts a gloved finger into the rectum and feels the prostate gland through the rectal wall to check for bumps or abnormal areas. The PSA test measures the level of PSA (a protein produced by the cells of the prostate gland) in the blood. PSA levels can rise due to cancer or benign (not cancerous) conditions. Doctors often use the PSA test and DRE as prostate cancer screening tests in men who have no symptoms of the disease.

To be eligible for the SELECT trial, participants had to have a DRE that found no signs of prostate cancer and a total PSA level less than or equal to 4.0 ng/ml.

During the trial, DREs and PSA tests are suggested, but not required, on an annual basis throughout the course of the study.

9. Who pays for these tests?

Physician, medical examination, and general clinic costs, including DREs, are charged to the participant in the same way as if he were not part of the trial. These costs may be covered by a participant's health insurance. Financial assistance may be available for some men. SELECT, however, pays for follow-up PSA tests. Men with questions about insurance coverage or reimbursement should check with their local SELECT site.

10. Who gets which supplement?

Men who participate in this study take two capsules a day. Participants were randomized (assigned by chance) to receive:

• selenium and vitamin E
• selenium and a placebo
• vitamin E and a placebo
• two placebos

Two placebos are used in the trial: one looks and tastes like a selenium capsule; the other looks and tastes like a vitamin E capsule. Each placebo contains only inactive ingredients. Neither the participants nor the researchers will know who is receiving the selenium and vitamin E, or the placebos, until the end of the study.

DSM Nutritional Products, Inc. (formerly Roche Vitamins, Inc.), Parsipanny, New Jersey, is donating bulk vitamin E and vitamin E placebo oils; Tishcon Corporation, Westbury, New York, is currently encapsulating the vitamin E and vitamin E placebo; and Sabinsa Corporation, Piscataway, New Jersey, is providing selenium and selenium placebo capsules at cost.

11. How much selenium is being used in SELECT? What risks might be involved?

The amount of selenium (provided as l-selenomethionine) is 200 ">micrograms (µg) daily. Although the initial results of the Nutritional Prevention of Cancer Trial showed an overall decrease in cancer incidence from selenium, a 2003 update reported 17 percent more new nonmelanoma skin cancers in the selenium group compared with the placebo group. It is not clear how these results would apply to men who did not already have skin cancer when they enrolled in SELECT, or to men who are not at increased risk for skin cancer.

12. How much vitamin E is being used in SELECT? What risks might be involved?

The amount of vitamin E (provided as dl-alpha-tocopherol acetate) is 400 milligrams (mg), which is equivalent to 400 International Units (IU) per day. This dose of vitamin E can thin the blood somewhat. Men with uncontrolled high blood pressure were not eligible to take part in SELECT because taking this much vitamin E might have increased their risk of stroke.

Vitamin E has been shown to increase the risk of some cardiovascular conditions. In a 2005 study, men and women with vascular disease or diabetes who took 400 IU of vitamin E daily for 7 years had a 13 percent increased risk of heart failure compared with participants taking a placebo. Heart failure is a condition in which the heart's ability to pump blood is weakened. A 2005 analysis of several studies in which people with various medical problems took vitamin E suggested a link between high doses of vitamin E (400 IU or more) and increased mortality.

13. What other requirements were there for SELECT participants?

Upon enrollment, men were asked to have toenail clippings collected to assess selenium levels in the body because selenium concentrates in fingernails and toenails. Toenails were chosen over fingernails because they take longer to grow and thus contain more history of someone's selenium intake. Blood samples were collected upon enrollment to assess levels of vitamin E.

Upon enrolling, men filled out a questionnaire on their diet and past supplement use. There is also an annual questionnaire that asks for updates of some of this information. Men do not have to change their diets during this study. Each man is offered a supply of a special daily multivitamin, manufactured by The Perrigo Company, Allegan, Michigan, that contains no selenium or vitamin E, to take if he chooses. Vitamin E, selenium, placebo capsules, and multivitamins will be provided free of charge to enrollees for the duration of the study.

Participants are asked to return to the study site every 6 months to pick up a 6-month supply of capsules.

14. What are the benefits of participating in SELECT?

Men involved in SELECT are partners in medical research that may decrease their chances of getting prostate cancer. Information learned from this study may also help future generations of men avoid this cancer.

15. What happens if a participant develops prostate cancer while involved in SELECT?

Participants diagnosed with prostate cancer during the study will be referred for treatment, will stop taking the study supplements, and will continue to be followed by the SELECT study staff, although less frequently.

Costs for diagnosis and treatment of prostate problems, prostate cancer, or other medical conditions during the study are charged to the participant in the same way as if he were not part of the trial. A participant's insurance will pay for diagnosis and treatment according to the plan's policies. If the participant has no insurance, social services may be available at the local level to cover costs for diagnosis and treatment.

16. What other clinical trials are under way for prostate cancer prevention?

In addition to SELECT, smaller trials are also being conducted with a variety of agents, including a vitamin D analog; soy isoflavones; and lycopene (a plant pigment common in tomatoes).

17. Where is more information about SELECT available?

In the United States and Puerto Rico, call the National Cancer Institute's Cancer Information Service at 1-800-4-CANCER (1-800-422-6237) for information in English or Spanish. People with TTY equipment can call 1-800-332-8615 for information in English. In Canada, call the Canadian Cancer Society's Cancer Information Service at 1-888-939-3333 for information in English or French.

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