title: Avoidance of late rectal toxicity after high-dose-rate brachytherapy boost treatment for prostate cancer.
abstract: To elucidate potential risk factors important for the appearance of late rectal toxicity (LRT) after high-dose-rate boost treatment (HDRBT) of prostate cancer and to validate the predictive value of the minimal dose to the most exposed 2 cc of rectum received with HDRBT (D2ccrect).
  
  
  
  The study of LRT, defined as relative deterioration of defecation problems (RDDP) (stool frequency, pain, rectal bleeding, fecal urgency, and incontinence) during follow-up period, was carried out on 88 patients, consecutively treated from October 2006 through April 2011 with HDRBT of 3 × 6-7 Gy to 50-50.4 Gy of EBRT. The impact of patients and treatment characteristics on third year prevalence of RDDP was analyzed by using binary logistic regression method.
  
  
  
  At third year of follow-up, RDDP was evidenced in 30 of 77 (39.0%) patients. More important as D2ccrect(OR, 1.15; 95% CI, 0.99-1.34; p = .059) was minimal dose to the most exposed 1 cc of the rectum (D1ccrect; OR, 1.15; 95% CI, 1.01-1.31; p = .032), whereas the sum of D1ccrectand EBRT mean rectal dose (EDmeanrect) was the only significant parameter in multivariate analysis (OR, 1.12; 95% CI, 1.04-1.22; p = .004). Based on a multivariate model, the safe compound 2 Gy equivalent dose was estimated at 44.4 Gy with the average ratio of D1ccrect:EDmeanrect= 1:3.1 (95% CI ± 1.8) and negative predictive value of 0.828.
  
  
  
  The study confirms the value of composite dose parameter and the importance of rectal high-dose and low-dose regions for LRT. Taking account of suggested dose constraints and CT/MRI-based HDRBT, the incidence of LRT can be reduced by a half.
authors.affiliation: Department of Brachytherapy, Institute of Oncology Ljubljana, Ljubljana, Slovenia. Electronic address: bkragelj@onko-i.si.
authors.forename: Borut
authors.initials: B
authors.lastname: Kragelj
authors.affiliation: Department of Brachytherapy, Institute of Oncology Ljubljana, Ljubljana, Slovenia.
authors.forename: Jernej
authors.initials: J
authors.lastname: Zlatic
authors.affiliation: University of Ljubljana, Faculty of Medicine, Department of Public Health, Ljubljana, Slovenia.
authors.forename: Lijana
authors.initials: L
authors.lastname: Zaletel-Kragelj
mesh_terms: D000368:Aged; D001918:Brachytherapy / Q000009:adverse effects*; D005242:Fecal Incontinence / Q000453:epidemiology* / Q000209:etiology; D006471:Gastrointestinal Hemorrhage / Q000453:epidemiology* / Q000209:etiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D058958:Organs at Risk / Q000000981:diagnostic imaging; D010146:Pain / Q000453:epidemiology* / Q000209:etiology; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000453:epidemiology* / Q000209:etiology; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000009:adverse effects*; D012007:Rectum / Q000000981:diagnostic imaging; D012307:Risk Factors; D014057:Tomography, X-Ray Computed
keywords: High-dose-rate brachytherapy; Late rectal toxicity; Prostate cancer D1cc; Prostate cancer D2cc