title: High dose-rate brachytherapy boost for intermediate risk prostate cancer: Long-term outcomes of two different treatment schedules and early biochemical predictors of success.
abstract: OBJECTIVE
  To report long-term cancer control rates following high dose-rate (HDR) brachytherapy boost for intermediate risk prostate cancer and explore early biochemical predictors of success.
  
  
  METHODS
  Results of two sequential phase II trials are updated and compared: (1) Single 15 Gy HDR-boost followed by external beam radiotherapy (EBRT) 37.5 Gy/15fractions, (2) Two HDR fractions of 10 Gy followed by EBRT 45 Gy/25fractions. Patients were followed prospectively for clinical and biochemical outcomes. Nadir PSA (nPSA) and PSA at 3-years were analyzed as continuous variables, and ROC analysis was used to identify the optimal cutoff values. Kaplan-Meier bDFS curves were generated and the log-rank test used to compare different groups
  
  
  RESULTS
  183 patients were accrued; 123 to the single fraction trial and 60 to the standard fractionation trial, with a median follow-up of 74 months and 99 months, respectively. The 5-year biochemical relapse-free survival was 97.4% and 92.7%, respectively (p=0.995). Median nPSA was 0.08 ng/ml. Failure to achieve a nPSA <0.4 ng/ml was associated with a significantly higher rate of biochemical relapse (5-year bDFS: 100% vs. 72%; p<0.0001).
  
  
  CONCLUSIONS
  HDR boost with single fraction 15 Gy provides durable long-term biochemical disease-free survival. PSA nadir <0.4 ng/ml is associated with very low risk of biochemical failure.
authors.affiliation: Sunnybrook Odette Cancer Centre, Canada; University of Toronto, Canada.
authors.forename: Joelle
authors.initials: J
authors.lastname: Helou
authors.affiliation: Sunnybrook Odette Cancer Centre, Canada; University of Toronto, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: D'Alimonte
authors.affiliation: Sunnybrook Odette Cancer Centre, Canada; University of Toronto, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Loblaw
authors.affiliation: Sunnybrook Odette Cancer Centre, Canada; University of Toronto, Canada.
authors.forename: Hans
authors.initials: H
authors.lastname: Chung
authors.affiliation: Sunnybrook Odette Cancer Centre, Canada; University of Toronto, Canada.
authors.forename: Patrick
authors.initials: P
authors.lastname: Cheung
authors.affiliation: Sunnybrook Odette Cancer Centre, Canada; University of Toronto, Canada.
authors.forename: Ewa
authors.initials: E
authors.lastname: Szumacher
authors.affiliation: Sunnybrook Odette Cancer Centre, Canada; University of Toronto, Canada.
authors.forename: Cyril
authors.initials: C
authors.lastname: Danjoux
authors.affiliation: Sunnybrook Odette Cancer Centre, Canada; University of Toronto, Canada.
authors.forename: Ananth
authors.initials: A
authors.lastname: Ravi
authors.affiliation: Sunnybrook Odette Cancer Centre, Canada.
authors.forename: Andrea
authors.initials: A
authors.lastname: Deabreu
authors.affiliation: Sunnybrook Odette Cancer Centre, Canada.
authors.forename: Liying
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Sunnybrook Odette Cancer Centre, Canada; University of Toronto, Canada. Electronic address: gerard.morton@sunnybrook.ca.
authors.forename: Gerard
authors.initials: G
authors.lastname: Morton
mesh_terms: D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D018572:Disease-Free Survival; D019583:Dose Fractionation, Radiation; D006801:Humans; D008297:Male; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000532:radiotherapy*; D012372:ROC Curve; D011829:Radiation Dosage; D012307:Risk Factors; D016896:Treatment Outcome
chemical_list: D017430:Prostate-Specific Antigen
keywords: Brachytherapy; HDR; PSA nadir; Prostate cancer; Single fraction