Local hyperthermia in treatment of experimental liver tumors

An experimental model for local microwave hyperthermia treatment of liver tumors is presented. Fifty-four Wistar rats were inoculated with a transplantable adenocarcinoma (NGW) in the central liver lobe. Ten to 16 days later 28 of the rats were exposed to local hyperthermia. A master thermistor placed in the liver parenchyma adjacent to the tumor controlled the hyperthermia, and the tumor-bearing liver lobe was maintained at 42.0 degrees C for 1 hour. At laparotomy 7 days after treatment, the tumor volume was measured. Four weeks after tumor inoculation, autopsy was performed. The tumor and the surrounding parenchyma was excised for histopathologic examination. A statistically significant reduction in tumor growth was found after exposure to local hyperthermia, the effect of hyperthermia being most pronounced in moderate-sized tumors (300-500 mm3 or 0.5-0.75 g). In larger tumors (greater than 900 mm3 or greater than 1.1 g) extensive necrosis developed after hyperthermia treatment. This indicates good tumoricidal effect even in large tumors, although this is not obvious if reduction in tumor growth is used as the only parameter to evaluate the effect of hyperthermia.