Antioxidants May Compromise Cancer Therapy

NEW YORK (Reuters Health) May 27 - 

A review of randomized trial data suggests that cancer patients should avoid the routine use of antioxidant supplements as they may diminish the efficacy of chemotherapy and radiation.

Still, findings from different studies are conflicting and, therefore, further research is warranted to determine whether antioxidants can be safely given during cancer therapy and whether any benefit is seen.

Although research looking at antioxidant use during cancer therapy has been on-going on for nearly two decades, it remains a controversial topic, lead author Dr. Brian D. Lawenda, from the Navel Medical Center in San Diego, California, and colleagues point out in the May 27th online issue of the Journal of the National Cancer Institute.

In investigating the impact of antioxidant use on radiotherapy, the researchers identified nine relevant studies, including two meta-analyses. Only three of the studies, however, were randomized controlled trials that specifically addressed the topic.

Results from the largest of the three trials suggested that antioxidant therapy reduced overall survival. However, there is evidence indicating that one antioxidant agent, amifostine, can protect certain healthy tissues from radiologic damage without increasing resistance in cancerous tissue.

Sixteen trials, including six that were placebo-controlled, were identified that looked at the effects of antioxidant supplementation on chemotherapy. There was no evidence that antioxidant use reduced treatment response rates, although the authors warn that none of the studies were really large enough to address this properly.

"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," Dr. Lawenda's team concludes.

J Natl Cancer Inst 2008;100:1-11.