Antitumor effects of local hyperthermia on a mouse fibrosarcoma

Local hyperthermia at 41-43 degrees C for 40 min prior to transplantation of a fibrosarcoma reduced its growth on the heated as well as the unheated contralateral legs of mice. The growth retardation was most pronounced in the unheated leg at 16 days interval between hyperthermia and tumor cell inoculation and was noticeable even at 22 days while in the heated leg it disappeared by the time. Inhibition of tumor growth was also independent of temperature and of the heating time at 43 degrees C. These results thus indicate that local hyperthermia induces both direct and abscopal antitumor effects which may probably be the result of a systemic effect of hyperthermia in the host animal.