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THE USE OF ANTIOXIDANTS IN CANCER THERAPY

Antioxidants wear the mantle of nutritional "superhero", as a result of their well proven preventative health benefits ranging from immune enhancement, to prevention of premature aging, cardiovascular disease and cancer. Hundreds of thousands of New Zealanders swallow antioxidant tablets every day, to super boost their dietary intake of antioxidant rich foods such as berries, green tea, garlic, turmeric and a range of fresh fruits and vegetables. There is however one area in which the merit of antioxidant supplementation is highly controversial. Do antioxidants help or hinder cancer patients undergoing conventional therapy with radiation or chemotherapy? Are they a panacea to minimise disturbing side effects, or even accentuate the efficacy of cancer treatments... or do they in fact detract from the effectiveness of such treatment?

One in nine New Zealanders will one day face a diagnosis of cancer and may well want an answer to these questions. The majority of New Zealand oncologists issue a blanket prohibition against the use of antioxidants concurrently with either chemotherapy or radiation therapy. In truth, this recommendation is based on theory, in vitro (test tube) and animal studies, with very little in the way of human data to back up their position. A close examination of these studies reveals a significant body of research providing evidence that antioxidant therapy can significantly reduce side effects from chemotherapy and radiation treatment. Some forms of antioxidant therapy have even been shown to increase the efficacy of these cancer therapies. So why the routine prohibition against antioxidant supplements during cancer treatment? Predominantly it seems to come down to the unstable molecules called "free radicals". Some of the cancer fighting properties of Radiation therapy and (less so) chemotherapy, result from the ability to produce huge amounts of free radicals which destroy the cell membranes and DNA of cancer cells, and unfortunately also destroy healthy cells. Antioxidants work to mop up and destroy free radicals, thus potentially reducing the efficacy of chemotherapy and radiation therapy. In truth, both radiation and chemotherapy kill cancer cells through numerous other mechanisms besides such free radical generation. Proponents of antioxidant therapy present a well substantiated argument that such therapeutic use of carefully chosen antioxidants along with chemotherapy or radiation treatment effectively reduces annoying and serious side effects, and even potentiates the effectiveness of the orthodox cancer therapy.

If you are the patient who has just been diagnosed with cancer and you're trying to make an informed decision on whether or not to use antioxidants as you undergo your cancer therapy, you have unwittingly stepped into a nutritional mine field. While arguments are equally strident on both sides of the debate, what is evident, according to renowned cancer researcher and medical writer Ralph Moss, is that we need more randomised controlled trial evidence to definitively claim that antioxidants are either a help or a hindrance in the treatment of cancer. To date the vast majority of such trials have been animal or test tube based studies. Moss strongly advises that cancer patients underging radiotherapy or chemotherapy, should not self medicate with antioxidants. However, he believes that when used wisely under the supervision of a trained practitioner, antioxidants have much to offer these patients. Moss also stresses that not all antioxidants are likely to be beneficial in their mode of action or effect, and that some may be ineffective or in fact may interfere with the therapeutic effects of both radiation and chemotherapy.

Kedar Prasad PhD from the University of Colorado, and formerly at the Centre for Vitamin and Cancer Research, is the author of 45 peer reviewed papers on this subject. Based on years of study, he believes that high dose antioxidant therapy can be harmless when added to chemotherapeutic or radiation therapy. Says Prasad, "experimental data and limited human studies suggest the use of nutrition approaches may increase oncologic outcomes and decrease toxicity". Prasad emphasises that we need to differentiate between the effects of what he calls "dietary antioxidants" which are nutrients commonly found in food; and those antioxidants produced in the body such as SOD and glutathione. These "endogenous" antioxidants may in fact protect cancer cells from destruction by radiation or chemotherapy if used during such therapy.

Prasad has another warning which is especially pertinent given standard advice from many oncologists. He has produced evidence that low dose antioxidants administered once shortly before chemotherapy or radiation therapy may actually be harmful by protecting both healthy and diseased cells. Ironically this directly contradicts the advice of many oncologists who caution their cancer patients to stay away from high dose antioxidants and instead use only vitamin and mineral complexes containing small amounts of antioxidants. Instead, says Prasad, if antioxidants are to be used in conjunction with radiation cancer therapy, they should be in high doses and administered before, during and after radiation or chemotherapy. Prasad's studies have also shown that a mixture of high dose dietary antioxidants is more effective in reducing the growth of cancer cells than individual antioxidants used in isolation.

A number of studies show that high dose antioxidant therapy enhances the effectiveness of radiation in the destruction of cancer cells, while simultaneously protecting normal healthy cells against injury. In particular, Prasad has demonstrated this effect with high doses of vitamins A, C, E and carotinoids. Conversely, there are no published studies anywhere which show that high doses of these antioxidants can protect cancer cells against radiation damage. Ironically, oncologists recommend that if such antioxidants are to be used during cancer therapy, their dosage should be limited to RDA (recommended daily allowance) levels. This despite the fact that animal studies show that when antioxidants such as vitamin E are given in a single low dose before radiotherapy, the efficacy of the cancer treatment is reduced.

When the antioxidants in question are the "endogenous" compounds produced within our body, such as cysteamine and glutathione, they have their own story. When these substances are given as antioxidant supplements before radiotherapy they protect both cancerous and healthy cells from the damaging effect of radiation. For this reason many experts recommend against the use of glutathione, lipoic acid or selenium in doses greater than the recommended daily allowance during radiation therapy.

Antioxidants also have much to offer in helping cancer patients recover from the rigors of radiation or chemotherapy treatment. Frequently, they are left malnourished or emaciated from the combined effect of their disease and their treatment. The intrinsic production of the body's own antioxidants often stays very low for a long period of time following such treatment, and many clinicians believe that it is important to increase antioxidant levels to normal as quickly as possible after therapy. Almost every vitamin from A to K has been found to be lacking in some cancer patients in the aftermath of chemotherapy. While an antioxidant rich diet helps in the process, many patients are unable to eat properly or digest or absorb food because of gastrointestinal damage from their cancer treatment. In these instances oral or IV antioxidant therapy can help to quickly restore healthy antioxidant levels to cells.

*Phytonutrients such as green tea, curcumin and genistein have been shown to enhance radiation induced death of cancer cells in addition to restraining tumour growth, in animal studies.

*High dose vitamin A, E and C therapy reduces weight loss and myelosuppression from chemotherapy.

*Supplementing with CoQ10 during chemotherapy with adriamycin reduces the commonly occurring congestive heart failure induced by the drugs, without in any way inhibiting the anti cancer effect.

*Selenium supplements enhanced the therapeutic effect of chemotherapeutic drugs such as Taxol and Andriamycin in animal studies.

*Maitake-d-fraction (medicinal mushroom) activates the immune system to kill cancer cells while leaving healthy cells unharmed. Administered along with chemotherapy or radiation it enhances therapy while reducing side effects.

*Shiitake Mushrooms have been shown to shrink tumours and prevent the spread of cancer. The effect has been shown to be synergistic with chemotherapy, as well as reducing the recurrence of breast cancer after surgery.

*DIM (extract of broccoli) inhibits the growth of both estrogen positive and negative breast cancer cells. DIM is synergistic with chemotherapeutic drugs such as tamoxifen.

*Columbia University Pediatric Oncology study found that children with a higher than average concentration of plasma antioxidants needed fewer dose reductions of chemotherapy; suffered fewer infections and had an increased quality of life; reduced chemotherapy toxicity and fewer days in hospital.

*Some chemotherapeutic drugs induce nerve damage. In a vitamin E trial, 73% of patients receiving chemo alone experienced neuropathy, while only 25% of the vitamin E supplemented group had this side effect.

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