Biological basis for the use of hyperthermia in tumour therapy

Hyperthermia in the temperature range 400 to 450C effectively kills cells. During continuous or after fractionated heating thermotolerance develops which correlates with the synthesis of heat shock proteins. Hyperthermia causes physiological and metabolic changes which modify thermosensitivity. Frequently radioresistant cells are thermosensitive and vice versa. Hyperthermia acts as a potent radiosensitizer when applied briefly before or after radiation exposure. The development of thermotolerance is strongly reduced under these conditions. For clinical use hyperthermia as a radiosensitizer appears to be a potent modality for radioresistant tumour cells lines. It should be used directly after radiation exposure. An individual selection of patients appears necessary. (orig.)