Inclusion of clinical risk factors into NTCP modelling of late rectal toxicity after high dose radiotherapy for prostate cancer

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, Riccardo Valdagni

Research output: Contribution to journalArticlepeer-review


Background and purpose: To fit an NTCP model including clinical risk factors to late rectal toxicities after radiotherapy for prostate cancer. Methods and materials: Data of 669 patients were considered. The probability of late toxicity within 36 months (bleeding and incontinence) was fitted with the original and a modified Logit-EUD model, including clinical factors by fitting a subset specific TD 50s: the ratio of TD 50s with and without including the clinical variable was the dose-modifying factor (D mod). Results: Abdominal surgery (surg) was a risk factor for G2-G3 bleeding, reflecting in a TD 50 = 82.7 Gy and 88.4 Gy 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. Conclusions: The inclusion of predisposing clinical factors improves NTCP estimation; the assessment of other clinical and genetic factors will be useful to reduce parameter uncertainties.

Original languageEnglish
Pages (from-to)124-130
Number of pages7
JournalRadiotherapy and Oncology
Issue number1
Publication statusPublished - Jul 2011


  • Dose-volume effects
  • NTCP models
  • Prostate radiotherapy
  • Rectal toxicity

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Hematology


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