Study in Finland Suggests Vitamin E Prevents Prostate Cancer
The latest analysis from a large prevention trial conducted by the National Cancer Institute (NCI) and the National Public Health Institute of Finland, shows that long-term use of a moderate-dose vitamin E supplement substantially reduced prostate cancer incidence and deaths in male smokers. The report was published in the March 18, 1998, issue of the Journal of the National Cancer Institute and the lead author is Olli P. Heinonen, M.D., D.Sc., of the Department of Public Health, University of Helsinki, Finland.
This report from the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study (ATBC Study) showed that 50- to 69-year-old men who took 50 mg of alpha-tocopherol (a form of the anti-oxidant vitamin E) daily for five to eight years had 32 percent fewer diagnoses of prostate cancer and 41 percent fewer prostate cancer deaths compared to men who did not receive vitamin E. The dose of vitamin E is equal to about 50 international units (the measure more commonly used with supplements) and is about three times the Recommended Dietary Allowance. The 29,133 male smokers from Finland were randomly assigned to receive alpha-tocopherol, mbeta-carotene (20 mg), or a placebo (inactive pill that looked like the vitamin) daily.
"These results give hope that a simple intervention may one day help reduce a man's chances of developing and dying from prostate cancer," said Demetrius Albanes, M.D., one of NCI's lead investigators on the study. "But it is important that other studies be done to confirm the beneficial effects of vitamin E. The ATBC Study and similar trials have shown us that supplements are not necessarily magic bullets and, more importantly, that what may be a beneficial supplement for some people may be harmful to others," said Albanes, who is in the Cancer Prevention Studies Branch of NCI's Division of Clinical Sciences.
As an example, he noted that earlier results from the ATBC Study showed that men who took the beta-carotene supplement had 16 percent more cases of lung cancer and 14 percent more lung cancer deaths than those who did not take beta-carotene. Men who drank large amounts of alcohol, and who took the beta-carotene, had higher rates of lung cancer than men who drank less alcohol.
In the current analysis, men taking beta-carotene supplements had more prostate cancer as well, but this increase was not statistically significant and was limited to men who drank alcohol. Men taking both nutrients (beta-carotene and vitamin E) had fewer cases of prostate cancer compared to men on placebo.
In men taking the vitamin E there was a reduction in clinically detectable prostate cancers beginning within two years of starting the supplement - a result which suggests to Philip R. Taylor, M.D., Sc.D., chief of NCI's Cancer Prevention Studies Branch, that vitamin E may be blocking a prostate tumor's progression to a more aggressive state. Most older men have microscopic areas of cancer in their prostate, few of which will progress to life-threatening disease.
"We know that prostate cancer develops first as latent cancer that can't be detected clinically," said Taylor. "For some men, these tumors are transformed from subclinical cancer - which may never affect a man's health - into aggressive disease. We think vitamin E is working by blocking the changeover from these more benign tumors to potentially life-threatening disease."
The investigators do not think that vitamin E affected symptoms that would cause a man to have medical attention that would lead to a diagnosis of cancer. Overall, men taking vitamin E had fewer diagnoses of later stage cancers than men not taking the supplement. The number of cancers diagnosed at earlier stages, when symptoms are few, was equivalent between supplement and placebo groups.
Prostate-specific antigen (PSA) testing was not common in Finland at the time of the study, and no other screening tests for prostate cancer were done as part of the ATBC Study. Most men diagnosed with prostate cancer had visited their physician with a complaint of urinary difficulties, while others sought medical care for other reasons, but mentioned urinary problems, which then were evaluated. Blood samples were taken from the ATBC participants during the study, and using these, an analysis of the value of blood PSA levels in predicting prostate cancer is under way.
In the United States, prostate cancer is the most frequently diagnosed cancer in males, with 184,500 cases expected in 1998 along with 39,200 deaths. African-American men have the highest rates of prostate cancer in the United States.
O.P. Heinonen, D. Albanes, J. Virtamo, P.R. Taylor, et al. Prostate cancer and supplementation with alpha-tocopherol and beta-carotene: incidence and mortality in a controlled trial. Journal of the National Cancer Institute1998; 90: 440-446.
The Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study Group. The effect of vitamin E and beta-carotene on the incidence of lung cancer and other cancers in male smokers. New England Journal of Medicine 1994;330:1029-35.
D. Albanes, O.P. Heinonen, P.R. Taylor, J. Virtamo, et al. Alpha-tocopherol and beta-carotene supplements and lung cancer incidence in the alpha-tocopherol, beta-carotene Cancer Prevention Study: effects of base-line characteristics and study compliance. Journal of the National Cancer Institute 1996;88:1560-70.
For a Q&A, please go to http://www.cancer.gov/newscenter/pressreleases/ATBCfollowupQA.