Clinical results of irradiation combined with local hyperthermia

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Abstract
This report updates a previous publication describing the experience at the Mallinckrodt Institute of Radiology with irradiation and hyperthermia in the treatment of superficial metastatic and recurrent malignant tumors. In a dose-seeking Phase I-II clinical study, a total of 101 lesions have been treated. Twenty-two tumors were treated with doses of irradiation ranging from 1000 to 3000 rad and the rest with doses between 3000 and 4000 rad. Irradiation was delivered twice weekly (every 72 hours) in tumor doses of 400 rad, usually with electrons (9–16 MeV). Hyperthermia was initiated within 30 minutes following irradiation, most of the patients being treated with 915 MHz microwaves, 41–43°C, for 60–90 minutes every 72 hours. Adequate temperatures were reached in most lesions measuring less than 2 cm in thickness, 70% of those 2–4 cm and only in 30% of those thicker than 4 cm. Of 36 measurable lesions in the head and neck, 20 had a complete response and 12 a partial response. In 16 of the 20 patients (80%) showing a complete response the tumor was controlled from three to 36 months. Of 30 adenocarcinoma of the breast lesions, recurrent in the chest wall, 16 showed a complete response and 9 a partial regression. Twelve of the 16 lesions that regressed completely (71.4%) showed long-lasting tumor control. Of 22 metastatic or recurrent melanoma lesions, 16 had a complete regression and six a partial response. Of the 16 patients with complete response, 13 (81%) had no evidence of recurrence lasting from three to 36 months. Three sarcoma lesions responded well to the combination of irradiation and heat and did not recur after treatment. Patients treated with doses larger than 3000 rad in the head and neck or in the chest wall (epidermoid carcinoma or adenocarcinoma, respectively) showed better tumor response than those treated with lower doses. However, in melanoma satisfactory results (80% or higher response) were observed with doses as low as 2000 rad. This combined therapy has been well tolerated by the normal tissues. In 6% of the patients there was evidence of tumor necrosis with ulceration and in 5% thermal burns which healed after 2 to 3 months, with conservative management. Subcutaneous fibrosis and some skin atrophy developed in about one third of the patients, probably due to the additional doses of irradiation delivered after previous definitive radiotherapy. These preliminary observations suggest enhanced tumor response and control after moderate doses of irradiation and hyperthermia. Efforts must be intensified to develop adequate equipment to satisfactorily produce heat and to measure temperatures in clinical settings, thus paving the way for appropriately designed clinical trials to test the efficacy of hyperthermia in patients with deep seated lesions and advanced primary tumors.

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