Interstitial thermoradiotherapy: A technical and clinical study of 29 implantations performed at the Institut Gustave-Roussy

In 1981, a protocol was developed at the Institut Gustave-Roussy, combining interstitial hyperthermia and brachytherapy. Twenty-nine implantations were performed in 23 patients. All the lesions except three were located in previously irradiated areas. The protocol consisted of interstitial hyperthermia, 44 degrees C for 45 min, immediately followed by iridium-192 brachytherapy, delivering a dose of 30 Gy in the first 17 implantations, and a dose of 40 Gy in the next 12 (the dose was increased because of two local relapses in the first 17 cases). Special 'metal-plastic' tubes have been designed to heat the tumour specifically and to spare the surrounding healthy tissues. Among the 25 implantations for which a complete thermal mapping was available, a minimum temperature of 44 degrees C was reached in 16 cases, 43 degrees C in 5 cases and 42 degrees C in 4. The temperature inhomogeneity within the treated volume was less than 1 degrees C in 16 cases, and up to 4 degrees C in only one instance. Short-term clinical results (at two months) are available for 23 implantations: a 100 per cent response rate and a 83 per cent complete regression rate was observed. Follow-up is still short for most patients and long-term local control cannot be evaluated. Treatment has been generally well tolerated despite prior irradiation. Thus, technically satisfactory hyperthermia could be obtained in most cases, short-term clinical results are encouraging, and the technique merits further study.