Intraperitoneal hyperthermic treatment of implanted peritoneal cancer in rats

The feasibility and efficacy of treating peritoneal cancer implants by applying heat to the peritoneal surfaces were studied in inbred Buffalo A rats given i.p. injections of Morris hepatoma 5123TC tumor cells. Heat was delivered to the peritoneum by contact with a heated physiological salt solution (Normosol-R) in the peritoneal cavity. A treatment temperature of 43.3 +/- 0.3 degrees was maintained for 30 min by an immersed stainless steel coil through which hot liquid circulated. Rats implanted with 0.5 to 1.0 x 10(8) tumor cells were treated at 1 to 4 hr (Group I), 4 to 5 days (Group II), and 22 to 24 days (Group III) after tumor implantation to simulate treatment for the clinical conditions of surgically spilled cancer cells, established microscopic cancer implants, and macroscopic cancer implants, respectively. A statistically significant improvement in survival was observed in Groups I and II compared with sham-treated control animals; 58% of the heat-treated animals were cured. Only a slight but statistically insignificant improvement was noted in Group III. These observations indicate that i.p. surface heat treatment of peritoneal implanted cancer is feasible and effective.