CUMULATIVE MINUTES WITH T(90) GREATER THAN TEMPINDEX IS PREDICTIVE OFRESPONSE OF SUPERFICIAL MALIGNANCIES TO HYPERTHERMIA AND RADIATION

Purpose: To better define thermal parameters related to tumor response in superficial malignancies treated with combined hyperthermia and ra diation therapy.Methods and materials: Patients were randomized to rec eive one or two hyperthermia treatments per week with hyperthermia giv en during each week of irradiation. Hyperthermia was given for 60 min with treatments begun within 1 hr following irradiation. Power was inc reased to patient tolerance or normal tissue temperature of 43.0-degre es-C. Irradiation was generally given 5 times per week with doses pres cribed to normal tissue tolerance (generally 24-70 Gy at 1.8-2.5 Gy pe r fraction). Multipoint thermometry was used with temperatures obtaine d every 5 min. Results: One hundred eleven individual treatment fields containing 1 or more tumor nodules were completely evaluable. The com plete and overall response rates were 46% and 80%, respectively. Forty -one percent of all treatment fields (51% of responding lesions) remai ned controlled at 2 years. Multivariate analysis revealed that the cum ulative minutes that the temperature achieved by 90% of the measured t umor sites (T90) was greater-than-or-equal-to 40.0-degrees-C, tumor hi stology, tumor volume, and radiation dose were significantly associate d with complete tumor response. The complete response rate was not sig nificantly affected by the number of hyperthermia treatments given per week. The incidence of clinically significant complications was low. Conclusions: These results support the usefulness of the cumulative mi nute system in describing time-temperature relationships. The signific ance of thermal variables with regard to tumor response strongly suppo rts the contention that hyperthermia can be a useful adjunct to irradi ation for the local control of cancer.