HOPE-TOO: NCI Comment on Published Results
A report published in the March 16, 2005 issue of the Journal of the American Medical Association finds no clear evidence that men and women who had vascular disease or diabetes and who took 400 i.u. of vitamin E daily for 7 years reduced their risk of cancer compared to others with these conditions who took a placebo 1. The study was not large enough to determine if vitamin E could prevent specific cancers. The report also showed that those taking vitamin E had a 13 percent increased risk of heart failure, a condition in which the heart's ability to pump blood is weakened. The report comes from a clinical trial called the Heart Outcomes Prevention Evaluation Study Extension (HOPE-TOO). These results emphasize the need to study vitamins and other natural products prior to making public health recommendations.
The National Cancer Institute (NCI), part of the National Institutes of Health, supports the Selenium and Vitamin E Cancer Prevention Trial (SELECT) in which men are taking 400 international units (i.u.) of vitamin E daily to determine if it prevents prostate cancer. SELECT has a Data and Safety Monitoring Committee (DSMC), a group of independent scientists, an ethicist, and a patient advocate. The DSMC periodically examines information about the study and new information that might affect the study to ensure the safety of the study participants. The DSMC for SELECT reviewed data from HOPE-TOO which was released in 2003 at a medical meeting. After that review, they determined SELECT should continue as designed. The DSMC will review the updated analysis from HOPE-TOO made available in this publication on March 18, 2005.
"NCI places the highest priority on the safety of participants in our clinical trials," said Leslie Ford, M.D., associate director for clinical research in NCI's Division of Cancer Prevention. "SELECT is an incredibly important study with major potential to reduce the burden of prostate cancer. Although HOPE-TOO evaluated cancer, it cannot answer the same scientific question posed by SELECT. We would like to see SELECT successfully completed to find out if vitamin E and selenium, together or alone, prevent prostate cancer. If at any time, however, the safety of the men in SELECT is at stake, we will make necessary changes to the study design or even stop the trial if needed."
NCI is also sponsoring the Women's Health Study, in which more than 39,000 healthy women age 45 and older took 600 i.u. of vitamin E or a placebo every other day for 10 years. This study was completed in March 2004 and results are being analyzed. NCI has no other long-term cancer prevention trials using vitamin E under way. NCI has never recommended that people take vitamin E outside a clinical trial for the prevention of cancer.
Background on SELECT
SELECT is a randomized, controlled clinical trial to determine if seven to twelve years of daily supplements of selenium and/or vitamin E reduces the number of new prostate cancers in healthy men. The trial aims to confirm earlier findings suggesting these nutrients may prevent prostate cancer.
In a study of selenium to prevent nonmelanoma skin cancer in 1,000 men and women, reported in 1996 2 , investigators found that taking the supplement for almost six and a half years did not reduce skin cancer. However, it did decrease the incidence of prostate cancer in men by more than 60 percent. A final analysis of the trial, published in 2002, showed a 52 percent reduction of prostate cancer in men taking selenium daily for an average of seven and a half years.3
Another trial, published in 1998 4, in which beta carotene and vitamin E were tested to prevent lung cancer in 29,000 Finnish men who smoked, showed that those men who took vitamin E had 32 percent less prostate cancer. Neither beta carotene nor vitamin E prevented lung cancer. A recent analysis of the levels of vitamin E in the blood of participants at the start of the trial showed that men with the highest levels of vitamin E in their blood had a lower risk of prostate cancer.5
SELECT is a double-blind randomized trial that includes 35,534 men age 55 and older and is conducted at more than 400 study sites across the United States (including Puerto Rico) and Canada. (African-American men in the trial were allowed to join at age 50 due to their high risk of developing prostate cancer.) One group takes 200 micrograms of selenium daily plus an inactive capsule, or placebo, that looks like vitamin E. Another group takes 400 milligrams of vitamin E daily along with a placebo that looks like selenium. A third group takes both selenium and vitamin E. A final group takes two placebos.
SELECT is coordinated by the Southwest Oncology Group, a national network of cancer researchers with headquarters in San Antonio, Texas.
Background on HOPE and HOPE-TOO
HOPE was a clinical trial of more than 9,500 men and women age 55 and older with vascular disease or diabetes. People in HOPE took the drug ramipril (a medicine to treat high blood pressure, sold as AltaceTM); a placebo (an inactive pill that looks like ramipril) and vitamin E; or a placebo (an inactive pill that looks like vitamin E) for 4.5 years to see if their risk of heart disease could be decreased. The primary diseases being studied were heart attack, stroke, and deaths from heart-related causes. Neither the people in the trial nor their physicians knew whether they were taking the active pills or the placebo. At the end of the initial study, ramipril showed a clear benefit in reducing these heart disease outcomes and that part of the trial was completed 6,7. All the participants were told whether they had been taking ramipril or the placebo, and those not taking ramipril were offered the drug. The people in the trial were also asked to continue taking vitamin E or the vitamin E placebo for 2.5 more years.
Of the original 9,500 people in HOPE, 3,994 continued to take vitamin E or placebo. In this extension of the original trial, now called HOPE-TOO, the researchers were looking at whether long-term vitamin E (400 i.u. daily for 7 years) reduces the risk of cancer, cancer death, and major heart disease outcomes. The final analysis showed no significant differences in the number of cancers or cancer deaths between those taking vitamin E and those on placebo. There were also no differences in the prespecified major heart disease outcomes, although there was a 13 percent increase in heart failure events.References:
1 The HOPE and HOPE-TOO Trial Investigators. Effects of Long-term vitamin E supplementation on cardiovascular events and cancer: A randomized controlled trial. JAMA 293:1138-1347, 2005.
2 Clark L.C., Combs GF Jr, Turnbull B.W., et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. Nutritional Prevention of Cancer Study Group. JAMA 276:1957-1963, 1996.
3 Duffield-Lillico AJ, Reid ME, Turnull BW, et al. Baseline characteristics and the effect of selenium supplementation on cancer incidence in a randomized clinical trial: A summary report of the Nutritional Prevention of Cancer Trial. Cancer Epid Biomarkers Prev 11:630-639, 2002.
4 Heinonen OP, Albanes D, Huttunen JK, et al. Prostate cancer and supplementation with alpha-tocopherol and beta-carotene: incidence and mortality in a controlled trial. J. Natl Cancer Inst 90:440-6, 1998.
5 Weinstein SJ, Wright ME, Pietinen P, et al. Serum alpha-tocopherol and gamma-tocopherol in relation to prostate cancer risk in a prospective study. J Natl Cancer Inst 97:396-399, 2005.
6 The Heart Outcomes Prevention Evaluation Study Investigators. Effects of an angiotensin-converting-enzyme inhibitor, ramipril, on cardiovascular events in high-risk patients. N Engl J Med 342: 145-153, 2000.
7 The Heart Outcomes Prevention Evaluation Study Investigators. Vitamin E supplementation and cardiovascular events in high-risk patients. N Engl J Med 342: 154-160, 2000.