SURFACE APPLICATORS FOR HIGH-DOSE-RATE BRACHYTHERAPY IN AIDS-RELATED KAPOSIS-SARCOMA

Purpose: The development of commercially available surface applicators using high dose rate remote afterloading devices has enabled radiothe rapy centers to treat selected superficial lesions using a remote afte rloading brachytherapy unit, The dosimetric parameters of these applic ators, the clinical implementation of this technique, and a review of the initial patient treatment regimes are presented, Methods and Mater ials: A set of six fixed-diameter (1, 2, and 3 cm), tungsten/steel sur face applicators is available for use with a single stepping-source (I r-192, 370 GBq) high dose rate afterloader. The source can be position ed either in a parallel or perpendicular orientation to the treatment plane at the center of a conical aperture that sits at an SSD of appro ximately 15 mm and is used with a l-mm thick removable plastic cap, Th e surface dose rates, percent depth dose, and off-axis ratios were mea sured, A custom-built, ceiling-mounted immobilization device secures t he applicator on the surface of the patient's lesion during treatment, Results: Between November 1994, and September 1996, 16 AIDS-related K aposi's sarcoma patients having a total of 120 lesions have been treat ed with palliative intent, Treatment sites were distributed between th e head and neck, extremity, and torso, Doses ranged from 8 to 20 Gy, w ith a median dose of 10 Gy delivered in a single fraction, Treatments were well tolerated with minimal skin reaction, except for patients wi th lesions treated to 20 Gy who developed moderate/severe desquamation , Conclusion: Radiotherapy centers equipped with a high dose rate remo te afterloading unit may treat small selected surface lesions with com mercially available surface applicators, These surface applicators mus t be used with a protective cap to eliminate electron contamination, T he optimal surface dose appears to be either 10 or 15 Gy depending upo n the height of the lesion. (C) 1997 Elsevier Science Inc.