INCREASED CHRONIC BOWEL COMPLICATIONS WITH SPLIT-COURSE PELVIC IRRADIATION

Purpose: To assess the possible impact of various treatment factors in cluding split-course versus continuous course treatment on the inciden ce of chronic bowel complications in patients receiving adjuvant pelvi c radiotherapy. Methods and Materials: A retrospective review was perf ormed of records of 153 patients treated with adjuvant external beam p elvic radiation therapy without brachytherapy for endometrial and colo rectal carcinomas. Continuous course radiotherapy was administered in 91 patients (59%) and 62 patients (41%) received split course treatmen t with a planned 2 week mid-treatment break. Mean pelvic dose and dail y fraction size were 51.4 and 1.71 Gray, respectively. Multiple patien t and treatment variables were assessed for their possible relationshi p to chronic bowel complications. Univariate and multivariate statisti cal analyses were carried out. Results: Twenty-seven patients (18%) de veloped chronic bowel complications at a median interval of 12 months after radiotherapy. Of all factors analyzed, only the use of split cou rse technique was associated with a significantly higher rate of chron ic bowel injury and decreased complication-free survival (p = 0.009). Conclusion: This study supports earlier suggestions that the use of sp lit course rather than continuous course pelvic radiotherapy can incre ase late intestinal complication rates. Possible pathophysiologic mech anisms are discussed.