Early side effects of radiation therapy seem to be a major limiting factor in treatment intensification for head and neck cancers. Correlations between the activity of Cu,Zn-superoxide dismutase (SOD), gluthatione peroxidase (GPX), gluthatione transferase (GST); the concentration of malonyldialdehyde (MDA), 7-ketocholesterol, and the severity of early mucosal radiation damage were studied in 90 patients treated with radical radiotherapy. Mucosal reactions were scored according to the Dische scale. Enzymatic activities were studied in erythrocytes, and concentrations of lipid oxidation were measured in blood plasma. The mean Cu,Zn-SOD activity before treatment was 947 U/g Hb, mean GPX activity 21 U/g Hb, MDA concentration in plasma 4.2 µg/l, MDA concentration in erythrocytes 0.19 µg/g Hb, and 7-ketocholesterol concentration 228 µg/l. Only gluthatione peroxidase (r=0.54) and gluthatione peroxidase/superoxide dismutase activity ratio (r=0.52) correlated with the severity of clinically observed early radiation damage. As a wide spectrum of the enzymatic activities was observed for the same level of normal tissue injury, it is not possible to predict the clinical radiosensitivity of individual patients from the estimation of the free radical enzymatic scavenging activity.

Keywords: radiation injury, Radiotherapy, gluthatione peroxidase, oxygen free radicals, Dose Fractionation