REPRODUCIBLE RAT MODEL FOR COMPARING LATE RECTAL TOXICITY FROM DIFFERENT BRACHYTHERAPY TECHNIQUES

Purpose: Newer brachytherapy techniques, such as pulse-simulated low d ose rate (PDR) and high dose rate (HDR) offer clinical and technical a dvantages over the conventional continuous low dose rate (CLDR) irradi ation, The impact of these techniques on late normal tissue toxicity h as remained largely undefined, with mathematical modeling and limited clinical experience providing some guidelines. We sought to develop a reproducible rat model for quantifying and comparing late rectal toxic ity from different brachytherapy techniques. Methods and Materials: An intrarectal applicator has been designed and techniques have been dev eloped to deliver clinically relevant doses of CLDR to allow compariso n to PDR and HDR, Female Wistar rats are utilized. The endpoints asses sed are rectal obstruction and a histological grading of late rectal i njury. Results: Analysis of 65 rats given either sham or single acute pulse irradiation has demonstrated the model to be reproducible and re liable in evaluating late rectal toxicity. Conclusions: The use of thi s rat model to compare late rectal injury from various doses, dose rat es, and fractionation parameters utilized by CLDR, PDR, and HDR will p rovide another tool for safely implementing these techniques into the clinical setting. (C) 1997 Elsevier Science Inc.