Implication of blood flow in sequencing hyperthermia and radiotherapy

The factors which determine the effectiveness of the combined use of heat and radiation in the treatment of malignant tumors are studied. The combined effect markedly varied depending on the order and time interval between the two modalities. An application of heat prior to irradiation caused greater skin damage as compared with that after irradiation. Probably the oxygenation of skin was improved due to an increase in blood flow by heat applied before irradiation. By contrast, an application of heat prior to irradiation was less effective than that after irradiation for tumor control. It appeared that tumors become hypoxic as a result of vascular damage by the heat applied prior to irradiation. It was concluded that heat should be applied after irradiation for maximum control with minimal normal tissue damage. (author). 14 refs, 3 figs, 1 tab