Stimulation of resistance to tumor growth of athymic nude mice pretreated by combined local hyperthermia and X-irradiation.

Host resistance to tumor growth was studied in athymic nude mice of C57BL background. Animals were pretreated in the left hind leg by local hyperthermia, local X-irradiation, or combined local hyperthermia and X-irradiation. Twenty-four hr posttreatment, the animals were inoculated with the metastatic Lewis lung carcinoma tumor. Half of the animals in each group were inoculated in the pretreated leg and animals of the other half of the group were inoculated in the contralateral untreated leg. An increase of 30 to 45% in life span was achieved in normal and nude mice pretreated by combined local hyperthermia and irradiation. The increase in life span was similar in animals inoculated in the pretreated leg or in the untreated contralateral leg. These results indicate that T-lymphocytes are not involved in the protection against tumor growth.