[Effect of moderate local hyperthermia in combination with chemotherapy with cyclophosphamide or N-nitroso- 1,3-bis(2-chloroethyl)urea(BCNU) on Yoshida sarcoma implanted in the descending colon of rats. 1. Repeated hyperthermia within 8 days and combination of chemotherapy followed by hyperthermia 24 h later].

The application of hyperthermia in cytostatic therapy has been discussed for a long time. Recently the question arose whether the chances of therapy might be improved by combining chemotherapy with hyperthermia. We used an inoculated gastrointestinal tumor to verify this hypothesis experimentally. 2 X 10(6) Yoshida sarcoma ascites cells were implanted in the descending colon of 101 Sprague-Dawley rats. A preternatural anus with two lumina was established concomitantly. Chemotherapy started on day 6 after surgery. 24 h later local hyperthermia was applied by means of a silicone tube inserted in the immobilized descending colon. The temperature in the tumor was raised to 43 +/- 0.5 degrees C. No acute toxic effects of hyperthermia were noted. The body temperature was kept from rising above normal by cooling. The differences in survival time between the chemotherapeutically treated groups and the control group were statistically validated. Additional hyperthermia did not result in additive effects. No advantage of hyperthermia alone was noted over the control. The results support scepticism about the therapeutic efficacy of hyperthermia and underline the necessity of further investigations in clinically adapted animal experiments.