Effect of whole-body hyperthermia on cell survival, metastasis frequency, and host immunity in moderately and weakly immunogenic murine tumors.

The effects of whole-body hyperthermia (WBH) on animal tumors and on metastasis frequency were studied. The tumors were a chemically-induced fibrosarcoma, FSa-I, which is moderately immunogenic and a spontaneously arisen fibrosarcoma, FSa-II, which is very weakly immunogenic. The WBH was given at 42.5 degrees in an incubator which had an auxiliary heater for accurate temperature control. Animal core temperature reached 41.5 degrees in 30 min. The lung colony assay revealed that the WBH for 60 min given at 24 hr after i.v. injection of single cells gave no lethal damage to either FSa-I or -II tumor cells. A significant inhibition of tumor growth was found when large tumors were given three daily WBH treatments. The frequency of lung metastasis was enhanced when large weakly immunogenic FSa-II tumors were treated by WBH, although no increase in the frequency was observed for FSa-I tumors of any size. Local hyperthermia did not significantly increase the metastasis rate of both tumors. These results suggest that the WBH might be useful for a treatment of large immunogenic tumors. However, the WBH is not a choice of treatment for possible micro-metastases.