Clinical and dosimetric predictors of late rectal syndrome after 3D-CRT for localized prostate cancer: Preliminary results of a multicenter prospective study

Purpose: To assess the predictors of late rectal toxicity in a prospectively investigated group of patients treated at 70 - 80 Gy for prostate cancer (1.8 - 2 Gy fractions) with three-dimensional conformal radiotherapy. Methods and Materials: A total of 1,132 patients were entered into the study between 2002 and 2004. Three types of rectal toxicity, evaluated by a self-administered questionnaire, mainly based on the subjective objective management, analytic late effects of normal tissue system, were considered: stool frequency/tenesmus/pain, fecal incontinence, and bleeding. The data from 506 patients with a follow-up of 24 months were analyzed. The correlation between a number of clinical and dosimetric parameters and Grade 2 or greater toxicity was investigated by univariate and multivariate (MVA) logistic analyses. Results: Of the 1,132 patients, 21, 15, and 30 developed stool frequency/tenesmus/pain, fecal incontinence, and bleeding, respectively. Stool frequency/tenesmus/pain correlated with previous abdominal/pelvic surgery (MVA, p=0.05, odds ratio [OR], 3.3). With regard to incontinence, MVA showed the volume receiving >= 40 Gy (V-40) (p=0.035, OR, 1.037) and surgery (p=0.02, OR, 4.4) to be the strongest predictors. V-40 to V-70 were highly predictive of bleeding; V-70 showed the strongest impact on MVA (p=0.03), together with surgery (p=0.06, OR, 2.5), which was also the main predictor of Grade 3 bleeding (p=0.02, OR, 4.2). Conclusions: The predictive value of the dose-volume histogram was confirmed for bleeding, consistent with previously suggested constraints (V-50 < 55%, V-60 < 40%, V-70 < 25%, and V-75 < 5%). A dose - volume histogram constraint for incontinence can be suggested (V-40 < 65 - 70%). Previous abdominal/pelvic surgery correlated with all toxicity types; thus, a modified constraint for bleeding (V-70 < 15%) can be suggested for patients with a history of abdominal/pelvis surgery, although further validation on a larger population with longer follow-up is needed. (c) 2008 Elsevier Inc.