Microwave-induced hyperthermia and radiotherapy in human superficial tumours: clinical results with a comparative study of combined treatment versus radiotherapy alone.

Eighty-five evaluable superficial recurrent malignant tumours, mainly adenocarcinomas (78 per cent), in 38 patients were treated with either combined local hyperthermia (41-45 degrees C for four sessions) and low dose radiotherapy (30.0 Gy) or the same low dose radiotherapy alone. The treatment was given for two weeks. Hyperthermia was induced externally with 2450 MHz or 915 MHz microwaves. Totally 57 tumours were given combined treatment with a complete and partial response rate of 46 and 30 per cent, respectively (duration 1-38 months). In 18 patients with 2-10 superficial tumours each, 56 tumours were used in a comparative study, comparing the effect of combined hyperthermia and low dose radiotherapy versus the same low dose radiotherapy alone, the patients acting as their own controls. The total response rates were 89 and 50 per cent, respectively, in the two treatment modality groups. The difference in response rates is significant (p = 0.0039) in favour of the combined treatment, and this is also found when comparing complete remissions only (p = 0.0027). Local pain and normal tissue reactions presented problems during and after 2450 MHz microwave-induced hyperthermia treatment, performed without a coupling water bag system. Introduction of 915 MHz microwave-induced hyperthermia with a coupling deionized water bag system and refinement of microwave applicators, as well as the temperature control system considerably reduced these problems.