Antioxidants Vitamin C and Vitamin E for the Prevention and Treatment of Cancer
Published in: Journal of General Internal Medicine, v. 21, no. 7, July 2006, p. 735-744
Posted on RAND.org on December 31, 2005
OBJECTIVE: To evaluate the evidence of the supplements vitamin C and vitamin E for treatment and prevention of cancer. METHODS: Systematic review of trials and meta-analysis. DATA SOURCES AND MAIN RESULTS: Thirty-eight studies showed scant evidence that vitamin C or vitamin E beneficially affects survival. In the ATBC Cancer Prevention Study Group, no statistically significant effect of treatment was seen for any cancer individually, and our pooled relative risk (regardless of tumor type) for a-tocopherol alone was 0.91 (95% confidence interval [CI]: 0.74, 1.12). All cause mortality was not significant. In the Linxian General Population Trial, the relative risks for cancer death for vitamin C (combined with molybdenum) was 1.06 (95% CI: 0.92, 1.21) and for vitamin E (combined with beta-carotene and selenium) was 0.87 (95% CI: 0.76, 1.00). We identified only 3 studies that reported statistically significant beneficial results: vitamin C (in combination with BCG) was found to be beneficial in a single trial of bladder cancer and vitamin E (in combination with alpha-3 fatty acid) increased survival in patients with advanced cancer. In the ATBC trial, in analyses of 6 individual cancers, the prevention of prostate cancer in subjects treated with a-tocopherol was statistically significant (RR=0.64, 95% CI: 0.44, 0.94). CONCLUSIONS: The systematic review of the literature does not support the hypothesis that the use of supplements of vitamin C or vitamin E in the doses tested helps prevent and/or treat cancer in the populations tested. There were isolated findings of benefit, which require confirmation.