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Treatment of superficial human neoplasms by local hyperthermia induced by ultrasound

This study was designed to test the safety and efficacy of local heating of superficial tumors by ultrasound. Twenty‐five patients were treated who had recurrent or metastatic tumor in superficial locations refractory to conventional treatment modalities. Heating was done with high intensity ultrasound fields produced by a 2 cm or 4 cm piezoelectric transducer at frequencies of 1‐3 MHz. Tumors were held at 43, 44, or 45 C center temperature for 30 minutes each treatment. Analysis of response was done after 6 treatments. Ultrasound and thermal fields were carefully mapped. Some nonuniformity of tumor heating was noted despite relatively uniform output of ultrasound energy by the transducer. Twenty‐one of the 25 patients were evaluable after 26 courses of local hyperthermia. Fourteen of 26 courses of treatment resulted in objective tumor response (54%) However, most responses were partial and median follow‐up time was short (5 weeks) because many patients had systemic disease and died or were put on chemotherapy after treatment. Eight of 12 lesions in patients with squamous cell carcinoma of the head and neck regressed. Response rate did not correlate with central tumor temperature. Treatment was, in general, well tolerated although 10/26 courses of treatment caused significant local pain. Pain always subsided after treatment. Five of 26 courses of treatment resulted in small (0.5 cm) cutaneous burns. Previous irradiation did not limit heating. We conclude that superficial tumors can be safely and effectively heated by ultrasound. Objective tumor responses were seen with hyperthermia alone, although we stress that, because of the short follow‐up time and, because most responses were partial, it is likely that the effects noted were transitory.