Written by Marcia Egles, MD. In a review of 19 studies with 1554 patients checking on the effects of antioxidant nutrients on chemotherapy found no evidence of interference with chemotherapy. Some trials showed better survival in the antioxidant group.
Is it helpful for chemotherapy patients to take antioxidant supplements? Antioxidant supplements, which include vitamins C, A, E and others, are taken by many people in the hope of preventing damage from free radicals.
Many of the drugs used in chemotherapy could be classified as “oxidants”, generating free radicals for the deliberate purpose of causing cell damage. The intended target for this damage is cancer cells, of course. There is therefore medical concern that the effectiveness of some types of chemotherapy could be hampered if antioxidants were taken at the same time. (1) A recent literature-search study found evidence supporting the use of antioxidant supplements during chemotherapy treatments.
The study involved five different electronic databases including MEDLINE, using search terms related to cancer treatments and antioxidants. Databases were searched from their inception up until the end of December, 2006. Foreign medical studies were included. The searches were duplicated independently by two researchers. Only randomized, controlled clinical trials which reported survival data or tumor response were included. Studies which used whole herbs and mixtures were excluded because of potential non-antioxidant properties. Of 845 references screened, 19 studies with a combined total of 1554 patients met the criteria for inclusion in the final review summary.
The 19 studies represented over 15 different cancers in various stages, 17 chemotherapeutic drugs and several antioxidants including glutathione, melatonin, vitamins A, C,and E, and ellagic acid.
For the specific cancers, agents, supplements and dosages, the reader is referred to the article’s “results” section and its extensive reference list.
The systematic review found no evidence that the effectiveness of chemotherapy was lessened by antioxidant supplication. Some trials reported better survival among the antioxidant groups. (2) Many of the studies reported decreases in toxicities among patients receiving antioxidants; decreased neurotoxicity with glutathione supplements (3, 4) was noted. The researchers caution the interpretation of these results, however, especially since most of the studies had very small sample sizes and were conducted in patients with advanced and or relapsed cancers. They emphasize the need for a large, well designed study of antioxidants used with chemotherapy.
Source: Block, Keith I., et al. “Impact of antioxidant supplementation on chemotherapeutic toxicity: a systematic review of the evidence from randomized controlled trials.” International Journal of Cancer 123.6 (2008): 1227-1239.
© 2008 Wiley-Liss, Inc
Posted July 23, 2008.
References:
- G.M. D’Andrea, Use of antioxidants during chemotherapy and radiotherapy should be avoided, CA Cancer J Clin 55(2005), p. 319-321.
- P. Lissoni, Five years survival in metastatic non-small cell lung cancer patients treated with chemotherapy alone or chemotherapy and melatonin: a randomized trial, J Pineal Res 35(2003),p.12-15.
- S.Cascinu etal. Neuroprotective effect of reduced glutathione on oxaliplatin-based chemotherapy in advanced colorectal cancer: a randomized, double-blind, placebo-controlled trial, J Clin Oncol 20 (2002) p.3478-3483.
- S. Cascunu et al. Neuroprotective effect of reduced glutathione on cisplatin-based chemotherapy in advanced gastric cancer: a randomized double-blind, placebo-controlled trial, J Clin Oncol 13 (1995), p. 26-32.
