Local hyperthermia at 41-43-degrees-C for 40 min prior to transplantat
ion of a fibrosarcoma reduced its growth on the heated as well as the
unheated contralateral legs of mice. The growth retardation was most p
ronounced in the unheated leg at 16 days interval between hyperthermia
and tumor cell inoculaton 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-deg
rees-C. These results thus indicate that local hyperthermia induces bo
th direct and abscopal antitumor effects which may probably be the res
ult of a systemic effect of hyperthermia in the host animal.