Antioxidants And Chemotherapy

Comments are being made that suggest vitamin supplementation is not a good idea. This is an example where it would be useful to scrutinise the source sponsorship. This does not imply anything sinister, simply the examination of more detail is desirable.

There is a paradoxical connection: antioxidants like vitamin E and beta-carotene interfere with the chemotherapy treatment of cancers where such treatments rely on free radicals attacking a tumour, yet antioxidants mop up free radicals. Radiation treatment kills tumours by inducing the creation of free radicals specifically to damage and destroy DNA and proteins. This is not a precise science and attempts to target cancerous tissue (tumour) will inevitably cause damage to healthy tissue. If chemotherapy is a treatment of last resort, the potential benefits far outweigh the risks. The commentary suggests a hypothesis, yet no evidence has been found that supports the hypothesis.

Plausible explanations why no evidence has been found (studies too small to observe significant differences) implies that the search for the required evidence will continue, even if no evidence is found. It implies that eventually the hypothesis will be proven even if no observation supports the possibility of a real theory being demonstrated. In a review of three (randomly selected) trials, one showed antioxidant supplementation was associated with lower survival rates. This is not surprising since antioxidants would destroy the free radicals before they can be of benefit when used to attack tumours. Antioxidant use while undergoing radiation (chemotherapy) treatment is contra-indicated. After the tumour has started to grow antioxidants could theoretically interfere with potential treatment, but neither is this supportive evidence or otherwise that antioxidants could prevent or slow down further tumour growth. Just interfere with chemotherapy.

Chemotherapy is chemical therapy (drugs). The observations could suggest that the therapy regimen is ineffective. It is even hypothetically possible that the drugs are dangerous and the reduced survival rates are linked to potentially lethal chemicals. No chemotherapy trials reported lower survival rates for patients on antioxidants, but the researchers said none of the studies was sufficiently large to spot such differences. The scientists declared in a written report (Journal of the National Cancer Institute):

"Despite some intriguing studies that have suggested the benefit of adjunctive antioxidant treatments in cancer patients the totality of the evidence is equivocal at best and leaves us with serious concerns about the potential for harm."