RESUMO
Reactive oxygen species (ROS) produced as a part of cellular metabolism can interact with biological macromolecules such as DNA, proteins and lipids and interfere with their normal functions, leading to the loss of cellular viability. ROS have been implicated in many pathophysiological conditions including cancer. In the present study, the damage caused by ROS and the effect of radiation in head and neck squamous cell carcinoma (HNSCC) patients were assessed in the erythrocytes by analyzing the superoxide dismutase (SOD) and catalase (CAT) activities, and levels of total thiols (T-SH) and malondialdehyde (MDA, a marker for lipid peroxidation). Blood samples were collected before the start of treatment and after the completion of radiotherapy. Both SOD and CAT activities were decreased in untreated patients, but elevated in patients after treatment. The T-SH levels were also depleted in untreated HNSCC patients, but elevated non-significantly after radiation therapy (p>0.05). The levels of MDA showed a significant increase in both untreated patients and after radiation therapy when compared with normal subjects (p<0.05). Thus, the present study indicated that the free radical-mediated damage was aggravated in untreated HNSCC patients, but the levels of antioxidants returned to baseline or nearly so after the treatment with radiation therapy.