title: Is single fraction 15 Gy the preferred high dose-rate brachytherapy boost dose for prostate cancer?
abstract: OBJECTIVE
  High dose-rate (HDR) brachytherapy is most commonly administered as a boost in two or more fractions combined with external beam radiotherapy (EBRT). Our purpose is to compare outcomes with a single fraction HDR boost to that with a standard fractionated boost in intermediate risk prostate cancer.
  
  
  METHODS
  Results of two sequential phase II clinical trials are compared. The Single Fraction protocol consists of 15 Gy HDR in one fraction followed by 37.5 Gy EBRT in 15 fractions over 3 weeks; the Standard Fractionation protocol consisted of two HDR fractions each of 10 Gy, 1 week apart, followed by 45 Gy EBRT in 25 fractions. Patients had intermediate risk disease, and were well balanced for prognostic factors. Patients were followed prospectively for efficacy, toxicity and health-related quality of life (Expanded Prostate Index Composite). Efficacy was assessed biochemically using the Phoenix definition, and by biopsy at 2 years.
  
  
  RESULTS
  The Single Fraction protocol accrued 123 patients and the Standard Fractionation protocol, 60. With a median follow-up of 45 and 72 months, respectively, the biochemical disease-free survival was 95.1% and 97.9% in the Single and Standard Fractionation trials (p=0.3528). Two-year prostate biopsy was positive in only 4% and 8%, respectively. There was no difference in late urinary or rectal toxicity rates, or in health-related quality of life between the two protocols.
  
  
  CONCLUSIONS
  The Single Fraction HDR protocol results in high disease control rate and low toxicity similar to our previous protocol using two HDR insertions, with significant savings in resources. While mature results with longer follow-up are awaited, a single 15 Gy may be considered as a standard fractionation regimen in combination with EBRT for men with intermediate risk disease.
authors.affiliation: Sunnybrook Odette Cancer Centre, Toronto, Canada. gerard.morton@sunnybrook.ca
authors.forename: Gerard
authors.initials: G
authors.lastname: Morton
authors.forename: Andrew
authors.initials: A
authors.lastname: Loblaw
authors.forename: Patrick
authors.initials: P
authors.lastname: Cheung
authors.forename: Ewa
authors.initials: E
authors.lastname: Szumacher
authors.forename: Manraj
authors.initials: M
authors.lastname: Chahal
authors.forename: Cyril
authors.initials: C
authors.lastname: Danjoux
authors.forename: Hans T
authors.initials: HT
authors.lastname: Chung
authors.forename: Andrea
authors.initials: A
authors.lastname: Deabreu
authors.forename: Alexandre
authors.initials: A
authors.lastname: Mamedov
authors.forename: Liying
authors.initials: L
authors.lastname: Zhang
authors.forename: Raxa
authors.initials: R
authors.lastname: Sankreacha
authors.forename: Eric
authors.initials: E
authors.lastname: Vigneault
authors.forename: Colvin
authors.initials: C
authors.lastname: Springer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods*; D018572:Disease-Free Survival; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D023381:Endpoint Determination; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011788:Quality of Life; D011879:Radiotherapy Dosage; D012044:Regression Analysis; D016896:Treatment Outcome