Hyperthermia in combination with definitive radiation therapy: results of a Phase I/II RTOG Study

Between August 1981 and April 1986, 133 patients with superficial malignant tumors not previously treated with radiotherapy were entered on a Phase I/II RTOG study evaluating hyperthermia plus definitive radiotherapy. Eligible patients included those with superficial epithelial or mesenchymal tumors less than 4 cm in depth. Protocol radiotherapy specified a tumor dose of 60 Gy delivered in 1.8-2.0 Gy fractions 5 times/week with a boost of 5-10 Gy through reduced portals to residual tumor. Protocol hyperthermia, delivered twice weekly, was to start within 15 minutes following irradiation and to consist of 60 minutes of heat to a tumor temperature of 43 degrees C. Sixteen patients were excluded. Of the 117 eligible patients, the treated lesions had site/histologies which were 35% head & neck/squamous, 46% breast/adenocarcinoma, and 19% other site/histologies. Lesions were 3 cm or larger for 77% of patients. Of the 41 patients with head & neck/squamous lesions, skin or subcutaneous necrosis occurred within 6 months for 2% of the patients; 12% experienced thermal blisters. Fourteen patients were followed for 6 months or more following start of treatment; none of these experienced late toxicities more severe than telangiectasis. Complete responses were observed in 51% of these patients. Of the 54 patients with breast/adenocarcinoma lesions, skin or subcutaneous necrosis occurred within 6 months for 13% of the patients; 17% experienced thermal blisters. Thirty-seven patients were followed for 6 months or more following start of treatment; complications observed during this period included 13% with ulceration and one case of skin necrosis. Complete responses were observed in 85% of these patients. Local control was maintained at nearly this level for at least 2 years. Logistic regression analyses showed site/histology, greatest tumor diameter and average tumor temperature to be significantly related to response. Based on these promising findings, the RTOG has instituted a randomized Phase III study evaluating radiation therapy with or without hyperthermia in this patient population.