More on Vitamin E and Prostate Cancer

ABSTRACT & COMMENTARY

Synopsis: Further analysis of the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study conducted in Finnish male smokers confirmed that a 32% decrease in the incidence of prostate cancer was seen in subjects taking alpha-tocopherol. Mortality from prostate cancer was reduced 41% in this group, but this study did not discuss overall mortality. The 1994 report of this study noted a significant increase in mortality from hemorrhagic stroke in subjects taking alpha-tocopherol. Thus, it remains unclear whether vitamin E supplementation reduces overall mortality.

Source: Heinonen OP, J Natl Cancer Inst 1998; 90:440-446.

The alpha-tocopherol, beta-carotene cancer Prevention Study (ATBC) entered 29,133 male smokers in Finland between the ages of 50 and 69 years between 1985 and 1988. Participants were randomly assigned to one of four intervention groups: alpha-tocopherol alone, beta-carotene alone, the combination of alpha-tocopheral and beta-carotene, or placebo. Supplementation was continued for a median of 6.1 years (range 5-8). The study was aimed to evaluate whether vitamin supplementation might lower the incidence of cancer-particularly lung cancer. Lung cancer deaths were not reduced in study participants. However, it appeared that persons taking alpha-tocopherol had a decreased incidence of prostate cancer. A total of 246 cases of prostate cancer have been detected in these men; 43 who received alpha-tocopherol alone, 56 in the alpha-tocopherol plus beta-carotene group, 80 in the group receiving beta-carotene alone, and 67 in the placebo group. Using the placebo group as a control, the incidence of prostate cancer was reduced 36% in the alpha-tocopherol group and 16% in the combination group. Those taking beta-carotene had a 20% increased incidence compared to placebo. Beta-carotene also led to a significant increase in lung cancers in the original study report.1

Sixty-two participants died from prostate cancer: 11 in the alpha-tocopherol group, 12 in the combination group, 21 in the beta-carotene group, and 18 in the placebo group. This difference of seven cases between placebo and alpha-tocopherol is translated to a statement that alpha-tocopherol decreases prostate cancer mortality by 41%.

COMMENTARY

It is highly disturbing to me that Heinonen and colleagues have not provided an update of overall mortality in this study. The fear of prostate cancer among American men is great, largely due to the high incidence of the disease and the risk of side effects of impotence and incontinence from its surgical treatment. It is only natural for men who fear prostate cancer to react to this selective report by running out and buying vitamin E supplements. While this report confirms a significant decrease in prostate cancer mortality, it is not at all clear that this beneficial effect is not counterbalanced by an untoward effect on other causes of mortality. In particular, the prior report of results of this study showed no evidence that vitamin E reduced overall mortality, and a significantly increased risk of hemorrhagic stroke was noted in patients who took vitamin E.1 Is it worth increasing one's risk of death from hemorrhagic stroke or some other catastrophe to lower the risk of dying from prostate cancer? Maybe it is, but people should have all the information from the study provided to them so they can make informed and reasoned choices. The final sentence of the paper is the following: "Before vitamin E can be recommended for prostate cancer prevention, further clinical trials are needed." This statement is certainly true in this instance, but the reader is never told why.

Reference

    1. The Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study Group. N Engl J Med 1994;330: 1029-1035.