Clinical Drug Experience Knowledgebase

Effect of Ascorbic Acid Oral Supplementation in Assessing the Severity of Oral Mucositis in Chemo-radiation Therapy of Head and Neck Cancers.

Oral mucositis is a predictable and unavoidable representation during the course of radiotherapy employed for treatment of head and neck cancers. The term oral mucositis is used to describe inflammation of the oral mucosa, a separate entity distinct from oral lesions with other pathogenic background generally summarized as stomatitis. The cells that line the gastrointestinal tract from the mouth to the rectum are especially vulnerable to such changes. The incidence and severity of oral mucositis is influenced by the type of antineoplastic treatment administered and patient related factors. The pathogenesis of radiation mucositis though not completely understood, is usually either by direct DNA damage or via an indirect mechanism of releasing free radicals upon radiolysis of water effecting the oral epithelium.It is associated with significant morbidity, pain, odynophagia, malnutrition thereby affecting the overall quality of life in these patients and carrying a more important risk of systemic infections particularly in impaired host defense setup.In addition to acute damage wide range of GI mucosal involvement occurs during radiotherapy.

Various radiation modifying agents have been used which can either selectively protect normal cells but not tumor cells against therapeutic damage or can selectively enhance the effect of radiation on tumor cells but not on normal cells thereby improving efficacy of radiation therapy. In spite of extensive research most of them are found to be toxic.

Antioxidants represent most selective radiation modifying agents that are non toxic to humans. However, because of many conflicting hypothesis on their usage affecting tumor response and also decreasing the radiation induced toxicity on normal cells, recommendations have followed for their non usage during chemo-radiotherapy. In spite of such reservations on behalf of oncologists over 70% of patients are on antioxidant supplements such as those containing vitamin A, vitamin C and polar carotenoids with or without the knowledge of oncologists.

Antioxidants can neutralize those free radicals generated during radio-chemo therapy enhancing body's antioxidant stores in order to prevent mucositis and to maintain healthy oral tissues. Literature survey provides exhaustive list of such antioxidants successfully implicated in controlling oral mucositis to some extent. Antioxidants such as beta carotene, vitamin E and vitamin C in combination, glutamine, glutathione have been studied.

Vitamin C is a water soluble nutrient that has wide antioxidant and wound healing properties. It has been widely in scurvy patients but its effect on conventional cancer therapy by radiation and chemotherapy were little known. Limited preclinical data suggested that this vitamin at high concentrations increased the toxicity of certain chemotherapeutic drugs in animals.

Recommended daily allowance (RDA) for vitamin C is 90mgper day for men and 75mg per day for women, upper limit being 2000mg per day. Evidence points out that the intake to achieve therapeutic tissue concentration in normal people should be several times higher than RDA. Conversely a recent study implicated dangers of consuming high doses of vitamin C which may turn from antioxidant to pro oxidant interfering radiotherapy. However it should be noted that the conditions used in the above study prevailed were invitro in nature, which cannot reflect an identical situation invivo. Few other studies believed that it can enhance immune function by increasing natural killer cells and lymphocyte activity.

With such controversial background and paucity of data in human intervention, this study is undertaken to evaluate the effect of vitamin c in assessing the severity of oral mucositis in patients undergoing cancer chemo and radiotherapy concurrently