Oxidative stress, a consequence of an imbalance between the formation and inactivation of reactive oxygen species, may be involved in the pathogenesis of many diseases including cancer. To evaluate the magnitude of oxidative stress, a study on the plasma levels of superoxide dismutase, total thiols, ascorbic acid and malondialdehyde (MDA) has been done in head and neck squamous cell carcinoma patients before the start of any oncological treatment and compared with healthy controls. The specific activity of superoxide dismutase in cancer patients is decreased significantly when compared to the control (p < 0.05). The total thiol and ascorbic acid levels are significantly reduced (p < 0.005) whereas MDA levels are significantly increased in the patients (p < 0.00005). Our findings show that the oxidative stress is elevated in cancer patients as evidenced by elevated levels of lipid peroxidation products and depletion of enzymatic and non-enzymatic antioxidants.

Human cell normally functions in a reduced state and a disturbance in the redox system precedes many pathophysiological conditions, including cancer. Radiation therapy exerts its own cytotoxic actions via production of free radicals in the body, which in turn, trigger many signaling pathways leading to apoptotic death of malignant cells but a systemic oxidative stress may intensify the condition of the disease. Ascorbic acid and thiols are the main plasma antioxidants which help fight these free radicals, and may correlate to the clinical response in head and neck cancer patients. The results of the present study indicate that thiols do not correlate but ascorbic acid correlates well to the clinical response.