• Tiziana Rancati, Claudio Fiorino, Gianni Fellin, Vittorio Vavassori, Emanuela Cagna, Valeria Casanova Borca, Giuseppe Girelli, Loris Menegotti, Angelo Filippo Monti, Francesca Tortoreto, Stefania Delle Canne, and Riccardo Valdagni.
• Prostate Program, Fondazione IRCCS Istituto Nazionale dei Tumori, Milano, Italy.
• Radiother Oncol. 2011 Jul 1; 100 (1): 124-30.

Background And PurposeTo fit an NTCP model including clinical risk factors to late rectal toxicities after radiotherapy for prostate cancer.Methods And MaterialsData of 669 patients were considered. The probability of late toxicity within 36months (bleeding and incontinence) was fitted with the original and a modified Logit-EUD model, including clinical factors by fitting a subset specific TD(50)s: the ratio of TD(50)s with and without including the clinical variable was the dose-modifying factor (D(mod)).ResultsAbdominal surgery (surg) was a risk factor for G2-G3 bleeding, reflecting in a TD(50)=82.7Gy and 88.4Gy for patients with and without surg (D(mod)=0.94; 0.90 for G3 bleeding); acute toxicity was also an important risk factor for G2-G3 bleeding (D(mod)=0.93). Concerning incontinence, surg and previous diseases of the colon were the clinical co-factors. D(mod)(surg) and D(mod)(colon) were 0.50 and 0.42, respectively for chronic incontinence and 0.73 and 0.64, respectively for mean incontinence score ⩾1. Best-fit n values were 0.03-0.05 and 1 for bleeding and incontinence, respectively. The inclusion of clinical factors always improved the predictive value of the models.ConclusionsThe inclusion of predisposing clinical factors improves NTCP estimation; the assessment of other clinical and genetic factors will be useful to reduce parameter uncertainties.Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

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