[Possibilities for optimizing radiotherapy of cancers of the ENT area by measuring oncoradiogenic enzyme peaks of glucose-6-phosphate isomerase].

Blood samples were taken from 39 patients with head and neck carcinomas after the initial irradiation, and the activity of the glycolytic enzyme glucose-6-phosphate isomerase (GPI) was measured. All patients showed GPI peaks at reproducible times. The height of the enzyme peak occurring 15.5-19.5 h after irradiation, was significantly correlated with tumour size and histological tumour differentiation. A late enzyme peak was associated with regional lymph node metastases. Possible sources of the enzyme peaks are discussed from a radiobiological point of view, and the value of such enzyme peaks for the optimization of radiation therapy is pointed out.