More on Antioxidants and Cancer Treatment

No issue better exemplifies the differences between conventional medical practice and that of complementary/integrative medicine than their recommendations about the use of herbs, vitamins, and nutraceuticals involving antioxidants (AO) in the treatment of cancer. Oncologists who practice conventional medicine typically recommend against supplements, based on their belief that they may interfere with the treatment benefits of radiation and chemotherapy (4).
Physicians who practice complementary medicine typically recommend in their favour, although often with caveats, because supplements can ameliorate the side effects of conventional treatment, and may also increase the effectiveness of conventional oncology protocols. Given that a high percentage of cancer patients use supplements, evaluating these opposing views is of considerable importance.
There have been numerous previous reviews of the evidence on this issue and many are conflicting (1-3), some recommending in favour of supplements and some against. In part this reflects the complexity of the issue, as there are many different kinds of supplements, each of which may have multiple properties. Moreover, radiation and chemotherapy may themselves be affected differently by supplements, as may different chemotherapy agents.
For any given cancer patient, whether to use or not use supplements is a complex decision. The greatest mistake is to adhere to a “one size fits all” approach. If conventional treatment for the patient’s malignancy has a high rate of success, prudence would suggest that a conservative approach is in order, although for some situations, such as radiation for head-and neck cancer, the side effects, while temporary, can be extremely debilitating. But for the great majority of cancer patients, conventional treatment is not effective, so that any detrimental effect of supplements, assuming that there were such an effect, is unlikely to change the treatment outcome. Moreover, given that some supplements have clear clinical evidence of providing benefit (melatonin, Vitamin D, PSK, and fish oil), while others have impressive support from animal models (curcumin, silibinin, lycopene, genistein, green tea, and ellagic acid), the possible benefits greatly outweigh the hypothetical harm. The most difficult part of the issue is the status of the most common AOs, vitamin A, beta-carotene, Vitamin C, and Vitamin E. While various combinations of these have been shown to reduce toxicity of conventional treatments, and there is no persuasive evidence that they interfere with conventional treatment outcomes, there is also no solid clinical evidence that they improve outcomes either. If they are to be used, it seems prudent to follow the advice of Prasad (1) and others to use them in combination at high doses. Experimental data and limited human studies suggest that use of these nutritional approaches may improve oncologic outcomes and decrease toxicity.

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