• Juan D Ospina, Jian Zhu, Ciprian Chira, Alberto Bossi, Jean B Delobel, Véronique Beckendorf, Bernard Dubray, Jean-Léon Lagrange, Juan C Correa, Antoine Simon, Oscar Acosta, and Renaud de Crevoisier.
• LTSI, Université de Rennes 1, Rennes, France; INSERM, U1099, Rennes, France; Escuela de Estadística, Universidad Nacional de Colombia Sede Medellín, Medellín, Colombia.
• Int. J. Radiat. Oncol. Biol. Phys. 2014 Aug 1; 89 (5): 1024-1031.

PurposeTo propose a random forest normal tissue complication probability (RF-NTCP) model to predict late rectal toxicity following prostate cancer radiation therapy, and to compare its performance to that of classic NTCP models.Methods And MaterialsClinical data and dose-volume histograms (DVH) were collected from 261 patients who received 3-dimensional conformal radiation therapy for prostate cancer with at least 5 years of follow-up. The series was split 1000 times into training and validation cohorts. A RF was trained to predict the risk of 5-year overall rectal toxicity and bleeding. Parameters of the Lyman-Kutcher-Burman (LKB) model were identified and a logistic regression model was fit. The performance of all the models was assessed by computing the area under the receiving operating characteristic curve (AUC).ResultsThe 5-year grade ≥2 overall rectal toxicity and grade ≥1 and grade ≥2 rectal bleeding rates were 16%, 25%, and 10%, respectively. Predictive capabilities were obtained using the RF-NTCP model for all 3 toxicity endpoints, including both the training and validation cohorts. The age and use of anticoagulants were found to be predictors of rectal bleeding. The AUC for RF-NTCP ranged from 0.66 to 0.76, depending on the toxicity endpoint. The AUC values for the LKB-NTCP were statistically significantly inferior, ranging from 0.62 to 0.69.ConclusionsThe RF-NTCP model may be a useful new tool in predicting late rectal toxicity, including variables other than DVH, and thus appears as a strong competitor to classic NTCP models.Copyright © 2014 Elsevier Inc. All rights reserved.

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