Vascular and cellular damage in a murine tumour during fractionated treatment with radiation and hyperthermia.

Tissue reactions and vascular damage in rat tumours (rhabdomyosarcoma R1H) were studied with morphological methods during fractionated treatments with 60Co-gamma-irradiation of 75 Gy alone and in combination with ten fractions of microwave hyperthermia at 43 degrees C, 60 min for five weeks. The nature and time course of tissue and vascular damage change individually with the treatment applied. During radiation-heat treatment congestion, dilation and rupture of tumour blood vessels were observed. The cellular and vascular damage, especially in the central parts of the tumours, occurred earlier and were generally more intense during the combined treatment than found after irradiation alone. The enhanced tissue damage can be related to the local temperatures in the R1H tumours during the microwave heat treatments.