During radiation and chemotherapy, cancer patients including prostate cancer patients, should avoid the routine use of antioxidant supplements unless approved by their doctor. Supplements may reduce the anticancer benefits of therapy, researchers concluded in a commentary published online in the Journal of the National Cancer Institute.

Radiation and Taxotere used for advanced prostate cancer therapy kill cells by inducing free radicals that then damage tumor DNA and proteins. It is a possibility that when we continue to take our antioxidant supplements may actually interfere with the therapies and reduce their anticancer activity. However, some investigators argue that taking antioxidant supplements protect healthy tissues and reduce the side effects of treatment. Despite two decades of research into this question, no clear answer has appeared.

Brian D. Lawenda, M.D., of the Naval Medical Center San Diego, evaluated the potential harms or benefits of antioxidant supplementation when udergoing radiotherapy or chemotherapy. He reviewed all of the randomized trials he could identify that tested the effect of antioxidant supplements on radiation therapy or chemotherapy.

In the case of radiotherapy, nine studies were identified that addressed the question, including two meta-analyses. Only three of these studies were randomized controlled trials designed to look at the clinical effect of antioxidant therapy on radiation. In the largest of the randomized trials, antioxidant supplementation was associated with a reduction in overall survival.

On the other hand, one antioxidant agent, amifostine, which is approved by the U.S. Food and Drug Administration to increase radiotherapy resistance in healthy salivary gland tissues, may protect normal tissues without increasing tumor radioresistance.

Lawenda also identified 16 randomized controlled trials that examined the impact of antioxidant supplementation on chemotherapy. Six of the trials were placebo-controlled.
Of the studies that included information on response rates, none reported a decrease in response in the antioxidant arm of the trial compared with the control arm. However, Lawenda cautions that none of the trials was large enough to reliably detect such differences.

Lawenda concluded that “Despite some intriguing studies that have suggested the benefit of adjunctive antioxidant treatments in cancer patients, the totality of the available evidence is equivocal at best and leaves us with serious concerns about the potential for harm.”


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