title: Rectal toxicity after intensity modulated radiotherapy for prostate cancer: which rectal dose volume constraints should we use?
abstract: BACKGROUND
  To define rectal dose volume constraints (DVC) to prevent ⩾grade2 late rectal toxicity (LRT) after intensity modulated radiotherapy (IMRT) for prostate cancer (PC).
  
  
  METHODS
  Six hundred thirty-seven PC patients were treated with primary (prostate median dose: 78Gy) or postoperative (prostatic bed median dose: 74Gy (adjuvant)-76Gy (salvage)) IMRTwhile restricting the rectal dose to 76Gy, 72Gy and 74Gy respectively. The impact of patient characteristics and rectal volume parameters on ⩾grade2 LRT was determined. DVC were defined to estimate the 5% and 10% risk of developing ⩾grade2 LRT.
  
  
  RESULTS
  The 5-year probability of being free from ⩾grade2 LRT, non-rectal blood loss and persisting symptoms is 88.8% (95% CI: 85.8-91.1%), 93.4% (95% CI: 91.0-95.1%) and 94.3% (95% CI: 92.0-95.9%) respectively. There was no correlation with patient characteristics. All volume parameters, except rectal volume receiving ⩾70Gy (R70), were significantly correlated with ⩾grade2 LRT. To avoid 10% and 5% risk of ⩾grade2 LRT following DVC were derived: R40, R50, R60 and R65 <64-35%, 52-22%, 38-14% and 5% respectively.
  
  
  CONCLUSIONS
  Applying existing rectal volume constraints resulted in a 5-year estimated risk of developing late ⩾grade2 LRT of 11.2%. New rectal DVC for primary and postoperative IMRT planning of PC patients are proposed. A prospective evaluation is needed.
authors.affiliation: Ghent University Hospital, Department of Radiation Oncology and Experimental Cancer Research, Belgium. Electronic address: Valerie.fonteyne@uzgent.be.
authors.forename: Valérie
authors.initials: V
authors.lastname: Fonteyne
authors.affiliation: Ghent University Hospital, Department of Radiation Oncology and Experimental Cancer Research, Belgium.
authors.forename: Piet
authors.initials: P
authors.lastname: Ost
authors.affiliation: Ghent University Hospital, Department of Radiation Oncology and Experimental Cancer Research, Belgium.
authors.forename: Frank
authors.initials: F
authors.lastname: Vanpachtenbeke
authors.affiliation: Ghent University, Biostatistics Unit, Department of Public Health, Faculty of Medicine and Health Sciences, Belgium.
authors.forename: Roos
authors.initials: R
authors.lastname: Colman
authors.affiliation: Ghent University Hospital, Department of Radiation Oncology and Experimental Cancer Research, Belgium.
authors.forename: Simin
authors.initials: S
authors.lastname: Sadeghi
authors.affiliation: Ghent University Hospital, Department of Radiology, Belgium.
authors.forename: Geert
authors.initials: G
authors.lastname: Villeirs
authors.affiliation: Ghent University Hospital, Department of Urology, Belgium.
authors.forename: Karel
authors.initials: K
authors.lastname: Decaestecker
authors.affiliation: Ghent University Hospital, Department of Radiation Oncology and Experimental Cancer Research, Belgium.
authors.forename: Gert
authors.initials: G
authors.lastname: De Meerleer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000209:etiology*; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects* / Q000379:methods; D012007:Rectum / Q000473:pathology* / Q000528:radiation effects*
keywords: Prostatic neoplasms/radiotherapy; Radiotherapy/intensity modulated/adverse effects; Rectum/radiation effects