Eugene Robertson Special Lecture. Hyperthermia from the clinic to the laboratory: a hypothesis.

Recently reported thermal isoeffective dose-response relationships in human tumours confirm the existence of an effect of hyperthermia in combination with radiotherapy. The prognostically important thermal doses are based upon the lowest temperatures achieved within tumours, and these thermal doses are well below those used in most laboratory studies that have provided the rational for hyperthermia treatment. Direct thermal cytotoxicity and thermal radiosensitization are insignificant at these low thermal doses. Other explanations for the mechanism of hyperthermia effect appear warranted. We hypothesize that hyperthermia at low thermal doses causes reoxygenation and hence direct radiosensitization in vivo.