Interaction of hyperthermia and radiation: radiation quality.

Cell-survival data were collected to determine the survival response of asynchronous CHO cells subjects to radiation and hyperthermia. The irradiation was at room temperature 100 minutes before exposure to hyperthermia at 42 degrees C. The survival response to the combination of these two agents is expressed by means of a survival surface, a three-dimensional concept relating cell survival to heat dose and radiation dose. The survival surface could be approximately described by a survival model comprising three components of cell killing: the unperturbed radiation component, the unperturbed hyperthermia component, and the interaction component. The dependence of the radiation component and the interaction component on radiation quality were investigated by irradiating with either 60Co gamma rays, 250 kV X rays or 14.7 MeV neutrons. An analysis suggests that the interaction component and the radiation component exhibit similar dependencies on radiation quality both for the deposition of damage and the repair or accumulation of that damage.