Local hyperthermia in combination with definitive radiotherapy: increased tumor clearance, reduced recurrence rate in extended follow-up.

Fifty-nine patients with superficial malignancies appropriate for treatment with definitive radiotherapy and technically suitable for application of local microwave hyperthermia were available for at least 6 months follow-up. Thirty-one of these patients presented with two lesions, only one of which was heated, the other serving as internal control. The responses of the lesions which were heated were compared with those receiving only radiation. The heated lesions responded more quickly, reconfirming observations previously made. However, at subsequent 6 months, 1 year, 18 months and 2 years follow-ups, tumor clearance was shown to be significantly more complete as compared with the internal controls. At 6 months follow-up complete response with combined therapy was observed in 27 of 31 lesions (87%) in contrast to complete response in 12 of 31 (39%) lesions treated with radiotherapy alone. At one year combined modality treatment produced complete response in 19 of 19 lesions (100%) while radiotherapy alone yielded complete response in 10 of 19 lesions (53%). At 18 months, 8 of 9 lesions (89%) treated with combined therapy remained controlled, 1 having recurred. Seven of 9 (78%) treated by radiotherapy alone were controlled, 2 having recurred. At 2 years, 6 patients were available for follow-up and 6 of 6 (100%) of lesions treated with combined modality remained controlled. Among those treated by radiotherapy alone, 5 of 6 (83%) remained controlled, while 1 recurred. The rate of tumor recurrence among the heated lesions was significantly lower than was found among the controls. The recurrence rate among the controls was similar to that expected in a similar group of patients treated with definitive radiotherapy. Therefore, in addition to its established capability to shrink tumors, hyperthermia in combination with radiotherapy has been shown to increase the rate of overall tumor clearance and reduce recurrences compared with that obtained from radiotherapy alone.