Single and fractionated whole body hyperthermia in murine fibrosarcoma

The effects of single and multiple fractionated whole body hyperthermia (WBH) 41.5 degrees C on benzo(a) pyrene induced fibrosarcoma of mice were evaluated in terms of tumour response and systemic alterations of the host. While single exposure of WBH(S) 2 hrs, caused moderate inhibition of tumours and increase in the median survival time, multiple fractionated exposures [WBH(M)] caused significant enhancement of tumours with decrease in mean survival time. Tumoricidal effects associated with increased acid phosphatase and beta-glucuronidase activity were observed in both the regimes of WBH. In WBH(M) the development of thermotolerance was indicated by decreased activity of these enzymes in subsequent treatments. Elevation of plasma corticosterone and significant lymphocytopenia occurred in both the regimes. The alterations were transient in WBH(S) but persisted for more than two weeks in WBH(M), indicating that tumour enhancement is possibly influenced by corticosterone-mediated immunosuppression. In the WBH(M), the tumoricidal effects were counteracted and surpassed by the growth stimulatory physiological alterations of the host. Therefore the mode of application of WBH and the systemic responses of the host are critical factors that should be considered in designing therapeutic regimes with WBH.