Antioxidants may undermine cancer therapy

NEW YORK (Reuters Health) - Cancer patients should perhaps avoid taking antioxidant supplements, a review of clinical trial data suggests, because they may diminish the effectiveness of chemotherapy and radiation treatment.

Still, findings from different studies are conflicting, so further research is warranted to determine whether antioxidants can be safely taken during cancer therapy and whether they have any benefit.

Although research looking at antioxidant use during cancer treatment has been on-going on for nearly two decades, it remains a controversial topic, note Dr. Brian D. Lawenda, from the Navel Medical Center in San Diego, California, and colleagues in their article in the Journal of the National Cancer Institute.

In researching the impact of antioxidant use on radiation therapy, the team identified three clinical studies that specifically addressed the topic.

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

Sixteen trials were identified that looked at the effects of antioxidant supplements on chemotherapy. There was no evidence that antioxidants 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," Lawenda's team concludes.

SOURCE: Journal of the National Cancer Institute, online May 27, 2008.