Possibilities for optimization of radiotherapy of esophageal carcinoma through measurement of the oncoradiogenic enzyme peak of glucosephosphate isomerase

: In 20 patients with oesophageal carcinoma blood samples were taken after the first irradiation and the activity of the glycolytic enzyme glucose-6-phosphate isomerase was measured. In all patients there occur GPI peaks at reproducible times. The height of the enzyme peak occurring 15.5 to 19.5 hours p.irr. expresses a significant dependence on tumour size and irradiation dose. The frequency of a late occurring enzyme peak depends on the appearance of regional lymph node metastases. Possible sources of the enzyme peaks are discussed from a radiobiological point of view and the meaning of such enzyme peaks for the optimization of radiation therapy is pointed out.