Identification of a rectal subregion highly predictive of rectal bleeding in prostate cancer IMRT.

To identify rectal subregions at risks (SRR) highly predictive of 3-year rectal bleeding (RB) in prostate cancer IMRT.

Overall, 173 prostate cancer patients treated with IMRT/IGRT were prospectively analyzed, divided into "training" (n=118) and "validation" cohorts (n=53). Dose-volume histograms (DVHs) were calculated in three types of rectal subregions: "geometric", intuitively defined (hemi-rectum,…); "personalized", obtained by non-rigid registration followed by voxel-wise statistical analysis (SRRp); "generic", mapped from SRRps, located within 8×8 rectal subsections (SRRg). DVHs from patients with and without RB were compared and used for toxicity prediction.

Training cohort SRRps were primarily within the inferior anterior hemi-rectum and upper anal canal, with 3.8Gy mean dose increase for Grade⩾1 RB patients. The SRRg, representing 15% of the absolute rectal volume, was located in 10 inferior-anterior rectal subsections. V18-V70 for SRRps and V58-V65 for SRRg were significantly higher for RB patients than non-RB. Maximum areas under the curve (AUCs) for SRRp and SRRg RB prediction were 71% and 64%, respectively. The validation cohort confirmed the predictive value of SRRg for Grade⩾1 RB. The total cohort confirmed the predictive value of SRRg for Grade⩾2 RB. Geometrical subregions were not RB predictors.

The inferior-anterior hemi anorectum was highly predictive of RB.

Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology. 2016 May 09 [Epub ahead of print]

Gaël Dréan, Oscar Acosta, Juan D Ospina, Auréline Fargeas, Caroline Lafond, Gwenaelle Corrégé, Jean-L Lagrange, Gilles Créhange, Antoine Simon, Pascal Haigron, Renaud de Crevoisier

INSERM 1099, Rennes, France; LTSI, Université de Rennes 1, Rennes, France., INSERM 1099, Rennes, France; LTSI, Université de Rennes 1, Rennes, France., INSERM 1099, Rennes, France; LTSI, Université de Rennes 1, Rennes, France., INSERM 1099, Rennes, France; LTSI, Université de Rennes 1, Rennes, France., INSERM 1099, Rennes, France; LTSI, Université de Rennes 1, Rennes, France; Département de radiothérapie, Centre Eugène Marquis, Rennes, France., Département de radiothérapie, Centre Eugène Marquis, Rennes, France., Hôpital Henri Mondor, France; UPEC, Université Paris Est Créteil, France., Centre Georges François Leclerc, Dijon, France., INSERM 1099, Rennes, France; LTSI, Université de Rennes 1, Rennes, France., INSERM 1099, Rennes, France; LTSI, Université de Rennes 1, Rennes, France., INSERM 1099, Rennes, France; LTSI, Université de Rennes 1, Rennes, France; Département de radiothérapie, Centre Eugène Marquis, Rennes, France. Electronic address: .