[Histopathologic changes and tumor cell kinetics after hyperthermia and/or radiation therapy in a rat glioma model:...

Single and combined treatment of interstitial microwave hyperthermia (HT) and radiation therapy (RT) were delivered to rat glioma models. The animal model tumors were induced by intracerebral inoculation of a small piece of G-XII glioma tissue to 6-8 week-old rats. Heating to about 44 degrees C at the surface of the inserting antenna using a 2450 MHz microwave was carried on for 30 minutes. A single dose of 800 r to the whole head was delivered by deep X-ray apparatus. In combined treatment, heating immediately preceded irradiation. Following treatment, animals were sacrificed at 1, 3, 6, 12, 24, 48, 72 and 96 hours. BUdR was administered intraperitoneally 1 hour before sacrifice. Microscopically, in HT, tumor cells became eosinophilic and separated from each other. Some of them were necrotic. Macrophage infiltration in tumor tissue was recognized after 72 hours. BUdR labelling indices were less than 1% till 24 hours had passed, then became 25% at 48 hours, nearly equal to that of the control animals. In RT, ballooning of the tumor cells was prominent, and some of the tumors became necrotic. Lymphocyte infiltration of the tumor tissue was occasionally seen. BUdR labeling indices decreased slowly; less than 10% in 24 hours, but continued until 96 hours had passed. Combined treatment of HT and RT showed addictive effect of histological changes and suppression of tumor cell growth.