Morphologic and morphometric studies on tumor necrosis produced by radiotherapy, and hyperthermia singly and in...

The purpose of the present study was to evaluate the therapeutic effects of hyperthermia associated with radiotherapy on neoplasia. Two transplanted experimental tumors (undifferentiated carcinoma of mouse breast and sarcoma 37) were used. A protocol was followed that included, for both models, four groups of animals: 1) control group; 2) radiotherapy group; 3) hyperthermia group; 4) radiotherapy associated with hyperthermia group. The animals were sacrificed after therapy according to a different schedule for each type of tumor. The morphology of the neoplasia in every group of treated tumors was compared with that of the control group. For quantitative evaluation of the necrosis, we studied the ratio of the tumor necrotic areas (N) to a tumor standard area (T). From the results obtained, the following conclusions were made: 1) Necrosis produced by combined treatment was significantly greater than that obtained by using one only; 2) necrosis appeared early after treatment and remained relatively unchanged; 3) The damaging effect of the hyperthermia occurred earlier than that produced by radiotherapy when these methods were used separately, thus suggesting distinct mechanisms of tumor necrosis.