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More Concern About Vitamin E Supplementation

Findings from a new randomized trial suggest that cancer patients should avoid antioxidant supplements.

With a few exceptions, results from clinical trials involving antioxidant vitamins have been disappointing (Journal Watch Mar 29 2005). This randomized, placebo-controlled Canadian trial was designed to assess whether antioxidants could reduce the incidence of second primary tumors or recurrence of first tumors among 540 patients who underwent radiation therapy for head and neck cancer. For the first 156 patients, active treatment included both daily vitamin E (400 IU) and ß-carotene (30 mg). However, midway through the trial, other studies revealed potential harm from ß-carotene; thus, active treatment included only vitamin E for the remaining 384 enrollees. Median follow-up was 52 months.

During the first 3.5 years of follow-up, while patients were taking supplements, the incidence of second primary cancers (mostly lung or trachea) or recurrence of first tumors was significantly higher in the vitamin group than in the placebo group (141 vs. 85 events per 1000 person-years). After 3.5 years, cancer incidence was lower with vitamin supplementation than with placebo, but 8-year estimated cancer-free survival still favored placebo. Notably, the early increase in cancer was seen even in the subgroup of patients who received only vitamin E.

Comment: These results are consistent with a theory that antioxidant vitamins can accelerate cancer progression, leading to earlier appearance of latent tumors. Although one should be cautious in extrapolating to other cancers, these findings suggest that cancer patients should avoid antioxidant supplements.

— Allan S. Brett, MD

Published in Journal Watch General Medicine May 3, 2005

Citation(s):

Bairati I et al. A randomized trial of antioxidant vitamins to prevent second primary cancers in head and neck cancer patients. J Natl Cancer Inst 2005 Apr 6; 97:481-8.

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