Hyperthermia by magnetic induction: II. Clinical experience with concentric electrodes.

Thirty-one patients with visceral or extensive superficial malignant tumors of various histologies and sites have been evaluated for our hyperthermia protocols employing magnetic induction at 13.56 MHz with concentric electrodes associated with a commercially available device. Response data in patients completing combined hyperthermia and radiation treatment was difficult to analyze because of the short survival of these patients with advanced disease. Acute toxicity, however, was limited to 2/31 patients with minor skin blistering from excessive superficial heating. In this report we focus on clinical thermometric results. In 6/31 (19%) of patients, portions of the tumor achieved greater than or equal to 42.5 degrees C. In 3/31 (10%), nearly all the tumor achieved greater than or equal to 42.5 degrees C. Those tumors successfully heated to greater than or equal to 42.5 degrees C throughout were relatively superficial. In 22/31 (71%), temperature greater than or equal to 42.5 degrees C were not achieved at any measured site. Maximum applied power levels were limited by development of painful superficial hot spots in 21/31 (68%), by diffuse discomfort or systemic intolerance in 9/31 (29%), by maximum power output from the generator in 1/31, or by other factors in 2/31 patients. Some patients had both local and systemic discomfort that limited power levels. Based upon analysis of the thermometric results, we discuss the anatomic sites and tumor depths for which this technique is most applicable.