The latest analysis of a large prevention trial conducted by the National Cancer Institute (NCI) and the National Public Health Institute of Finland showed 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, md, dsc, 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 daily for 5 to 8 years had 32% fewer diagnoses of prostate cancer and 41% fewer prostate cancer deaths, as compared with men who did not receive vitamin E. The dose of vitamin E is equal to about 50 international units and is about three times the recommended dietary allowance (RDA). The 29,133 male smokers from Finland were randomly assigned to receive alpha-tocopherol, beta-carotene (20 mg), or a placebo daily.
More Research Needed
These results give hope that a simple intervention may one day help reduce a mans chances of developing and dying from prostate cancer, said Demetrius Albanes, md, one of NCIs 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, continued Dr. Albanes, who is in the Cancer Prevention Studies Branch of NCIs 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% more cases of lung cancer and 14% more lung cancer deaths than those who did not take beta-carotene. Men who drank large amounts of alcohol and took 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 those who drank alcohol. Men taking both beta-carotene and vitamin E had fewer cases of prostate cancer compared to men receiving placebo.
Vitamin May Block Tumor Progression
In men taking the vitamin E supplement, there was a reduction in clinically detectable prostate cancers beginning within 2 years of starting the supplement. According to Philip R. Taylor, md, dsc, chief of NCIs Cancer Prevention Studies Branch, this result suggests that vitamin E may be blocking a prostate tumors 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 cant be detected clinically, said Dr. Taylor. For some men, these tumors are transformed from subclinical cancer which may never affect a mans health into aggressive disease. We think vitamin E is working by blocking the changeover from these more benign tumors to potentially life-threatening disease.
No Effect on Cancer Symptoms
The investigators do not think that vitamin E affected symptoms that would cause a man to seek 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 in the 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 performed 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 were then evaluated. Blood samples were taken from the ATBC participants during the study, and an analysis of PSA levels is underway.