Clinically derived dose effect relationship for hyperthermia given in combination with low dose radiotherapy

Abstract

A group of 36 patients, treated on 44 fields with fractionated treatments of local high-frequency induced hyperthermia and radiotherapy to the low total dose of 14–25 Gy, was retrospectively evaluated for differences between responders (i.e., complete and partial responders) and non-responders. A response rate of 86% was achieved, comprising 14% (6/44) complete and 73% (32/44) partial response. There was an indication that the probability of complete response is greater in smaller tumours. The tumour temperatures achieved were higher in the responders than in the non-responders. Logistic analysis was performed on the mean temperature achieved. This temperature parameter yielded a significant positive doseeffect relationship with regard to therapeutic effect, from which a 50% effective dose of 38.8°C was calculated. The data indicate that to obtain the maximum therapeutic effect, i.e., >95% response rate, tumour temperatures above 42.5°C need to be achieved.