title: Predictive Parameters of Symptomatic Hematochezia Following 5-Fraction Gantry-Based SABR in Prostate Cancer.
abstract: OBJECTIVE
  This study identified predictors of high-grade late hematochezia (HH) following 5-fraction gantry-based stereotactic ablative radiation therapy (SABR).
  
  
  METHODS
  Hematochezia data for 258 patients who received 35 to 40 Gy SABR in 5-fractions as part of sequential phase 2 prospective trials was retrieved. Grade 2 or higher late rectal bleeding was labeled HH. Hematochezia needing steroid suppositories, 4% formalin, or 1 to 2 sessions of argon plasma coagulation (APC) was labeled grade 2. More than 2 sessions of APC, blood transfusion, or a course of hyperbaric oxygen was grade 3 and development of visceral fistula, grade 4. Various dosimetric and clinical factors were analyzed using univariate and multivariate analyses. Receiver operating characteristic (ROC) curve analysis and recursive partitioning analysis were used to determine clinically valid cut-off points and identify risk groups, respectively.
  
  
  RESULTS
  HH was observed in 19.4%, grade ≥3 toxicity in 3.1%. Median follow-up was 29.7 months (interquartile range [IQR]: 20.6-61.7) Median time to develop HH was 11.7 months (IQR: 9.0-15.2) from the start of radiation. At 2 years, cumulative HH was 4.9%, 27.2%, and 42.1% in patients who received 35 Gy to prostate (4-mm planning target volume [PTV] margin), 40 Gy to prostate (5-mm PTV margin), and 40 Gy to prostate/seminal vesicles (5-mm PTV margin), respectively (P<.0001). In the ROC analysis, volume of rectum receiving radiation dose of 38 Gy (V38) was a strong predictor of HH with an area under the curve of 0.65. In multivariate analysis, rectal V38 (≥2.0 cm(3); odds ratio [OR]: 4.7); use of anticoagulants in the follow-up period (OR: 6.5) and presence of hemorrhoids (OR: 2.7) were the strongest predictors. Recursive partitioning analysis showed rectal V38 < 2.0 cm(3), and use of anticoagulants or rectal V38 ≥ 2.0 cm(3) plus 1 other risk factor resulted in an HH risk of >30%.
  
  
  CONCLUSIONS
  Rectal V38 and 2 clinical factors were strong predictors of HH following 5-fraction SABR. Planning constraints should keep rectal V38 below 2.0 cm(3).
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Hima Bindu
authors.initials: HB
authors.lastname: Musunuru
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Department of Medical Physics, Odette Cancer Centre, Toronto, Ontario, Canada.
authors.forename: Melanie
authors.initials: M
authors.lastname: Davidson
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Patrick
authors.initials: P
authors.lastname: Cheung
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Danny
authors.initials: D
authors.lastname: Vesprini
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Stanley
authors.initials: S
authors.lastname: Liu
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Hans
authors.initials: H
authors.lastname: Chung
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: William
authors.initials: W
authors.lastname: Chu
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Mamedov
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Department of Medical Physics, Odette Cancer Centre, Toronto, Ontario, Canada.
authors.forename: Ananth
authors.initials: A
authors.lastname: Ravi
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: D'Alimonte
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Kristina
authors.initials: K
authors.lastname: Commisso
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Joelle
authors.initials: J
authors.lastname: Helou
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Andrea
authors.initials: A
authors.lastname: Deabreu
authors.affiliation: MacroStat, Inc, Toronto, Ontario, Canada.
authors.forename: Liying
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada; Department of Health Policy, Measurement and Evaluation, University of Toronto, Toronto, Ontario, Canada. Electronic address: andrew.loblaw@sunnybrook.ca.
authors.forename: Andrew
authors.initials: A
authors.lastname: Loblaw
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D057908:Argon Plasma Coagulation; D001803:Blood Transfusion; D019583:Dose Fractionation, Radiation; D057918:Fiducial Markers; D006471:Gastrointestinal Hemorrhage / Q000145:classification / Q000209:etiology* / Q000628:therapy; D006484:Hemorrhoids / Q000150:complications; D006801:Humans; D006931:Hyperbaric Oxygenation; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000601:surgery*; D012372:ROC Curve; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods; D012002:Rectal Diseases / Q000145:classification / Q000209:etiology* / Q000628:therapy; D012003:Rectal Fistula / Q000209:etiology; D012007:Rectum / Q000528:radiation effects; D012044:Regression Analysis; D012669:Seminal Vesicles