• Claudio Fiorino, Gianni Fellin, Tiziana Rancati, Vittorio Vavassori, Carla Bianchi, BorcaValeria CasanovaVC, Giuseppe Girelli, Marco Mapelli, Loris Menegotti, Simona Nava, and Riccardo Valdagni.
• Department of Medical Physics, Ospedale San Raffaele, Milan, Italy. fiorino.claudio@hsr.it
• Int. J. Radiat. Oncol. Biol. Phys. 2008 Mar 15; 70 (4): 1130-7.

PurposeTo 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 MaterialsA 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.ResultsOf 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>or=40 Gy (V40) (p=0.035, OR, 1.037) and surgery (p=0.02, OR, 4.4) to be the strongest predictors. V40 to V70 were highly predictive of bleeding; V70 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).ConclusionsThe predictive value of the dose-volume histogram was confirmed for bleeding, consistent with previously suggested constraints (V50<55%, V60<40%, V70<25%, and V75<5%). A dose-volume histogram constraint for incontinence can be suggested (V40<65-70%). Previous abdominal/pelvic surgery correlated with all toxicity types; thus, a modified constraint for bleeding (V70<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.

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