Is there evidence to limit a patient's intake of antioxidants such as vitamin C during radiation to prevent detrimental outcomes?

Many cancer patients take mega-doses of antioxidants in the hope of reducing treatment related side effects, improving the odds of cure and/or preventing second primary cancer. Unfortunately, high quality trials addressing these issues are lacking and available data are largely limited to pre-clinical animal models. Although there are some reports of improved acute toxicities with the use of antioxidants during radiation therapy, there are at least a handful of studies showing a detriment.

The largest study was conducted in Canada by Bairati et al. 540 pts with stage I and II H&N squamous cell carcinoma were randomized to supplementation with 400 IU vitamin E and beta-carotene 30 mg daily vs. placebo, starting with radiation and continued fo...