THERMORADIOTHERAPY IN THE MANAGEMENT OF SUPERFICIAL MALIGNANT-TUMORS

In recent years there have been numerous randomized and nonrandomized studies conducted to assess the efficacy of hyperthermia combined with either radiation therapy or chemotherapy, especially in the treatment of superficially seated malignant tumors, The major impact of hyperth ermia is currently on locoregional control of tumor. Heat may be direc tly cytotoxic to tumor cells or inhibit repair of both sublethal and p otentially lethal damage after radiation, These effects are augmented by the physiological conditions in tumors which lead to states of acid osis and hypoxia, Blood flow is often impaired in tumor relative to no rmal tissue, and hyperthermia may lead to a further decrease in blood flow and augment heat sensitivity, Three major areas of clinical inves tigation have borne the greatest fruit for hyperthermia as adjunctive therapy to radiation therapy, These include recurrent and primary brea st lesions, melanoma, and head and neck neoplasms, The thermal enhance ment ratio was increased in all cases and is estimated to be 1.4 for n eck nodes, 1.5 for breast, and 2 for malignant melanoma, In general, t he most important prognostic factors for complete response are radiati on dose, tumor size, and minimal thermal parameters (minimum thermal d ose, mean minimum temperature or temperature exceeded by 90% of therma l sensors), The number of heat fractions administered per week appears to have no bearing on the overall response, which may be indicative o f the effects of thermotolerance. The total number of heat fractions d elivered also appears to be irrelevant provided adequate heat is deliv ered in one or two sessions, The major prognostic factors for the dura tion of local control are tumor histology, concurrent radiation therap y dose, tumor depth, and mean minimum temperature.