livingmed.com Blog

ANTIOXIDANTS AND CANCER TREATMENT

February 4th, 2008

An important paper on the interaction of antioxidants and radiation therapy was recently published in the International Journal of Cancer. Interestingly, despite the significance of its findings, this study has received virtually zero attention from the scientific community or the media.
As background, in April 2005, Isabelle Bairati, MD, PhD, and her colleagues at the Hôtel-Dieu de Québec Research Centre and the  Université Laval completed a ten-year study on the interaction of antioxidants and radiation therapy. This was hailed as the first placebo-controlled, double-blind, randomized trial assessing the effect of supplementation with antioxidant vitamins during radiation therapy. The study concluded that supplements of synthetic beta-carotene (30 mg per day) or alpha tocopherol (400 IU per day) had a harmful effect on cancer patients. In particular, the authors claimed that the cancer recurrence rate was 40 percent higher among patients who had been randomly assigned to the supplementation arm of the trial. They therefore called on patients and physicians to exert caution in using antioxidants until new evidence could be provided by future trials.
Kedar Prasad, PhD, and other proponents of the concurrent use of antioxidants during cancer treatment criticized the Bairati paper. They were disappointed that Bairati and colleagues had used ordinary alpha tocopherol as their choice of vitamin E when Prasad’s previous work had shown that it was not just alpha tocopherol but alpha tocopherol succinate that had the anticancer efficacy. They also felt that natural forms of the vitamin were more effective than synthetic, drug store-type vitamins. But, by and large, the medical world accepted the Bairati trial as definitive proof that antioxidants interfered with radiation therapy. Word spread like wildfire in oncology circles, confirming a long-held belief that antioxidants interfered with standard cancer treatments such as radiation and chemotherapy. The take away message, as stated in a Université Laval press release, was that “Supplements May Speed Up Development of Cancer.” Advocates of complem! entary and alternative medicine (CAM) were confounded by this large and impressive study.
But now the other shoe has dropped.
In December 2007, Dr. Bairati and her Québec colleagues published a major modification of their previous conclusions. Further analysis revealed, they said, that the danger of synthetic antioxidants was limited to one particular sub-population: cigarette smokers – specifically, those who continued to smoke during radiation treatment. The authors analyzed the outcome in 540 patients who had been given radiation for head and neck cancers. During the follow-up period, 119 patients had a recurrence of their disease and 179 died. Smokers were the group with the worst prognosis. However, astonishingly, smoking in the period leading up to or following radiation therapy did not modify the effects of the two supplements. It was only smoking during the course of radiation therapy that led to a statistically significant increase in the risk of a recurrence. It was a large enough increase to skew the statistics for the group as a whole, leading to the erroneous conclus! ion that antioxidants interfered with radiotherapy in the general patient population.
Statistically, increased risk is generally expressed as a “hazard ratio” (abbreviated HR). In this study, current smokers had an HR of 2.41 for recurrence, in other words more than double the chance of a recurrence compared to the rest of the patient population. The HR for death from any cause was a similar 2.26. But the hazard ratio for dying of their initial head and neck cancer was a whopping 3.38 in patients who got radiation, smoked and also received a single synthetic antioxidant.
“These results could best be explained by the hypothesis that the combined exposures reduced the efficacy of radiation therapy,” Bairati and her colleagues now say. “Particular attention should be devoted to prevent patients from both smoking and taking antioxidant supplements during radiation therapy” (Meyer 2007).
According to the National Cancer Institute, 85 percent of head and neck cancers are linked to tobacco use. (Alcohol use further exacerbates this trend.) This has been widely known for years, and so it is shocking that there are still people so hopelessly addicted to tobacco that they not only continue to smoke after they’ve been diagnosed with head and neck cancer but continue to smoke right through their radiation therapy. It was in this subset of particularly unhealthy individuals that antioxidants were associated with an increased risk of disease progression. As Bairati and colleagues suggest, such individuals should definitely not compound their problems by then taking a synthetic antioxidant.
But the more important lesson for patients and practitioners is that antioxidants do NOT generally interfere with the effects of radiation therapy, as was previously suggested. They do NOT increase the risk of a recurrence, of death from head and neck cancer, or of overall mortality in the average patient. In this updated study, the harmful effect of synthetic antioxidants was entirely limited to those relatively few tobacco-addicted patients who continued to smoke during their radiation therapy. Thus, the major premise underpinning oncologists’ condemnation of antioxidants during radiation therapy has crumbled, although few seem to have noticed so far.

References:
Bairati I, Meyer F, Jobin E, et al. Antioxidant vitamins supplementation and mortality: a randomized trial in head and neck cancer patients. Int J Cancer. 2006;119:2221-4.

Bairati I, Meyer F, Gélinas M, et al. Randomized trial of antioxidant vitamins to prevent acute adverse effects of radiation therapy in head and neck cancer patients. J Clin Oncol. 2005;23:5805-5813.

Bairati I, Meyer F, Gélinas M, et al. A randomized trial of antioxidant vitamins to prevent second primary cancers in head and neck cancer patients. J Natl Cancer Inst. 2005;97:481-488.

Meyer F, Bairati I, Fortin A, et al. Interaction between antioxidant vitamin supplementation and cigarette smoking during radiation therapy in relation to long-term effects on recurrence and mortality: A randomized trial among head and neck cancer patients. Int J Cancer. 2007 Dec 4;122(7):1679-168.

Entry Filed under: Uncategorized