THERMORADIOTHERAPY OF SUPERFICIAL AND SUBSURFACE TUMORS - ANALYSIS OFTHERMAL PARAMETERS AND TUMOR RESPONSE

Between 1988 and 1993, 57 superficial and subsurface tumours of variou s tumour type were treated with a 430-MHz microwave heating device. Me an (range) tumour depth of the 57 tumours was 3.0 (0.5-6.5) cm. Fifty- four tumours were treated with thermoradiotherapy. Total radiation dos e ranged from 20 to 70 Gy with a mean of 53 Gy. For the remaining thre e tumours, thermochemotherapy was performed. Hyperthermia was given on ce a week, and a total of 207 heat sessions was administered. Our goal of hyperthermia treatment was to elevate all monitored tumour points > 41 degrees C for > 30 min. The mean (range) number of intratumoral t hermometry points was 3.7 (2-6). The goal of hyperthermia treatment wa s achieved in 49% of the sessions. At the time of maximum tumour regre ssion, complete response was noted in 53% of the tumours treated with thermoradiotherapy. Univariate analysis demonstrated that parameters i ncluding tumour type (breast cancer versus others), tumour depth, mini mum tumour temperature, average tumour temperature, minimum equivalent time at 43 degrees C, and number of heat sessions achieving the treat ment goal significantly affected the tumour response of the combined t reatment, while total radiation dose and number of heat sessions were not significant factors for tumour response. Multivariate logistic ana lysis revealed that only tumour depth ( < 3 versus greater than or equ al to 3 cm) was a significant prognostic factor for tumour response (p = 0.029). Tumour type (breast cancer versus others) and a number of h eat sessions achieving the treatment goal (0-1 versus 2-5) were found to be of borderline significance in the multivariate analysis (p = 0.0 75 and 0.097 respectively). The number of heat sessions achieving a mi nimum tumour temperature of > 41 degrees C for > 30 min seems a practi cal thermal parameter that influences tumour response. The present stu dy indicates the importance of quality and quantity of heat session on the treatment outcome of thermoradiotherapy.