The effects of heat and radiation on cancers implanted on the feet of mice.

Abstract

Heating of S91 melanoma in DBA/1 mice or S-180 in SWR mice to 44 deg C for from 30 to 40 minutes destroyed a high proportion of the tumors without damage to the feet on which the tumors were implanted. Heat and radiation were synergistic or at least additive in their effects on tumors when treatments with heat and radiation were given within a few hours of each other regardiess of which agent was administered first. Moderate exposures to heat and radiation when given close together cured some radioresistant tumors that could not be cured by larger doses of radiation without destroying the mice's feet. Small tumors were more radiosensitive than large ones, and large ones were more heat- sensitive than small ones. After exposure to one-third of a lethal dose of heat, tumors and normal tissues became heat-resistant and were not damaged by exposures that normally destroy them. Tumors were transplantable immediately after exposures to heat that are lethal to them when they are left in situ. Injection of serotonin into tumors enormously increased their susceptibility to heat. Repeated injections of serotonin without heating resulted in inhibition of growth rate of S-91 melanomas. The chemical changes of the inflammatorymore » reaction that follows heating should be studied in the hope of developing cancerocidal compounds whose injection might reproduce the destructive effects of heat on cancer. (auth)« less