Thermal tolerance

Interest in the use of hyperthermia for tumour therapy has increased significantly during the past few years. There are a number of aspects of thermal killing at the cellular level which may be important in this regard. One has come to be known as thermal tolerance or induced thermal resistance. This may be manifested as a “resistant tail” on cell survival curves for heating times longer than about two to four hours. Thermal tolerance has been reported on numerous occasions and for Chinese hamster cells is especially dramatic for temperatures ranging between 40° and 42.5°C. At these temperatures the longest continuous heating times usually reported are in the range of 14 hours or less (Dewey et al., 1977; Harisiadis et al., 1977; Sapareto et al., 1978; Henle et al., 1978; Raaphorst et al., 1979).