• 9/20/2005
  • New York, NY
  • staff
  • Cancerpage.com

Antioxidant vitamins may reduce the severity of adverse effects of radiation therapy but may increase the risk of recurrence of the underlying tumor, according to a report by Canadian researchers.

Although many patients take vitamin and mineral supplements in the hope of improving cancer treatment outcomes, the authors point out, few studies have examined the efficacy and safety of adjuvant antioxidant vitamin supplementation in this setting.

Dr. Isabelle Bairati from Laval University Cancer Research Center, Quebec City and colleagues examined whether daily supplementation with alpha-tocopherol and beta-carotene could reduce the rate and severity of acute adverse effects of radiation therapy in 540 patients with head and neck cancer.

Severe acute adverse effects during radiation therapy occurred in fewer patients in the supplement group (19.2%) than in the control group (24.8%), the authors report in the August 20th issue of the Journal of Clinical Oncology.

There was a tendency for less severe adverse effects during radiation therapy at any site and overall among those receiving antioxidants, the results indicate. Combined treatment with alpha-tocopherol and beta-carotene was associated with a significant 62% reduction in adverse effects overall and a similar reduction among patients with cancer of the larynx.

However, local recurrence of tumor was 37% more likely among patients in the supplementation group, the investigators report, and was somewhat higher among patients treated with both antioxidants.

In light of these findings, the researchers observe that “randomized controlled trials should be conducted to provide clear scientific evidence regarding the efficacy and safety of antioxidant use as adjuvant therapies for cancer.”

In an accompanying editorial, Dr. Kevin Camphausen and associates from the National Cancer Institute, Bethesda, Maryland agree, pointing out that “the issue of patient self-supplementation with antioxidants during radiotherapy must also be addressed in more detail given the results of this study.”

“Without any definitive data on this issue,” they conclude, ” a reasonable approach would be to avoid unnecessary supplementation during and after radiotherapy.”

Source:
J Clin Oncol 2005;23:5805-5813,5455-5457