[Optimizing radiotherapy for carcinomas of the tongue and floor of the mouth. Measurement of oncoradiogenic enzyme peaks of GPI].

After a first irradiation with 2 and 5 Gy blood samples were collected at 30 minutes' intervals for 24 hours in 19 tongue cancer patients to assess the activity of the glycosis enzyme glucose-6-phosphate isomerase (GPI) and the creatine kinase (CK). In all patients the GPI activity exhibited peaks at reproducible points in time. Observed for the very first time, this GPI peak had a height at 15 to 18 hours following radiation that correlated with the tumor volume and the irradiation dose. We refer to it as the oncoradiogenic enzyme peak. The frequency of the appearance of a late enzyme peak is significantly related to the presence of regional lymph node metastases. The radiobiological considerations regarding the potential causes for such post-irradiation increases in enzyme activity are discussed. The impact of demonstrating oncoradiogenic GPI peaks for optimizing radiotherapy is outlined.