Effect of elevated temperature on experimental swarm rat chondrosarcoma.

The effect of hyperthermia on Swarm rat chondrosarcoma viability was investigated in Sprague-Dawley rats. The tumor blocks (0.33 g per block) were heated to 40 degrees C, 50 degrees C, 60 degrees C, 70 degrees C, and 80 degrees C, respectively. Blocks that were not heat treated served as controls. Three heating sessions (10, 20, and 30 minutes) were performed for each heating group. The tumor blocks were transplanted into 4-week-old Sprague-Dawley rats to observe tumor growth. The tumor cells of the control, 40 degrees C (3 time sessions), and 50 degrees C (10 minutes) groups showed little difference from each other microscopically before and 5 weeks after transplantation. Microscopic evidence of cell destruction was observed immediately after hyperthermia in the groups treated at 50 degrees C (20 minutes) and higher. No tumor growth was found in these groups 35 weeks after implantation. Type II collagen, the specific collagen produced by the tumor, was analyzed with the Northern blot hybridization method. The mRNA could not be identified in the groups treated at > 50 degrees C (20 minutes) at 5 weeks after implantation. This study indicates that the growth of Swarm rat chondrosarcoma was retarded at temperatures > 50 degrees C (20 minutes). The Swarm rat chondrosarcoma is a useful model for studying the effects of hyperthermia on malignant tumor growth.