HYPERTHERMIA IN CANCER-TREATMENT .1.

In recent years there have been. numerous randomized and nonrandomized studies conducted to assess the efficacy of hyperthermia combined wit h either radiation therapy or chemotherapy especially in the treatment of superficially seated malignant tumors. The major impact of hyperth ermia is currently on loco-regional control of tumor. Heat mag be dire ctly cytotoxic to tumor cells or inhibit repair of both sublethal and potentially lethal damage after radiation. These effects are augmented by the physiological conditions in tumor which lead to states of acid osis and hypoxia. Blood flow is often impaired in tumor relative to no rmal tissue, and hyperthermia mag lead to a further decrease in blood now and augment heat-sensitivity. Three major areas of clinical invest igation have borne the greatest fruit for hyperthermia as adjunctive t herapy to radiation therapy. These include recurrent and primary breas t lesions, melanoma, and head and neck neoplasms. Thermal enhancement ratio was increased in all cases and is estimated to be 1.4 for neck n odes, 1.5 for breast and 2 for malignant melanoma. In general, the mos t important prognostic factors for complete response are radiation dos e, tumor size and minimal thermal parameters (minimal thermal dose (t( 43min)), mean minimal temperature (T-min) or T-90, i.e., temperature-e xceeded by 90% of thermal sensors). The number of heat fractions admin istered per week appear to have no bearing on the overall response, wh ich may be indicative of the effects of thermotolerance. The total num ber of heat fractions delivered also appears irrelevant provided adequ ate heat is delivered in one or two sessions. The major prognostic fac tors for the duration of local control are tumor histology, concurrent radiation therapy dose, tumor depth T-min.