title: Utility of 5-alpha-reductase inhibitors in active surveillance for favourable risk prostate cancer.
abstract: BACKGROUND
  This retrospective review compares prostate-specific antigen (PSA) doubling time (DT) prior to the initiation of a 5-alpha-reductase inhibitor (pre-5-ARI) to after the PSA nadir (post-nadir) has been reached for patients on active surveillance for favourable-risk prostate cancer.
  
  
  METHODS
  Between 1996 and 2010, a total of 100 men with a history of 5-ARI use were captured from our active surveillance database. Twenty-nine patients had a sufficient number of PSA values to determine both pre-5-ARI and post-nadir DTs. PSADT was calculated using the general linear mixed-model method.
  
  
  RESULTS
  The median follow-up was 69.5 months. The median pre-5-ARI PSADT was 55.8 (range: 6-556.8) months, while the post-nadir value was 25.2 (range: 6-231) months (p = 0.0081). Six patients were reclassified after an average of 67.7 (range: 59-95) months, due to progression in PSADT (n = 2) or Gleason score (n = 4). The median pre-5-ARI and post-nadir DTs for this group were 42.3 (range: 32.4-91.1) and 21.1 (range: 6-44.3) months, respectively.
  
  
  CONCLUSIONS
  5-ARIs significantly decreased PSADT compared to prior to their initiation. This effect may be due to preferential suppression of benign tissue following PSA nadir. The resulting PSADT would then represent a more accurate depiction of the true cancer-related DT. If validated with a larger cohort, 5-ARIs may enhance the utility of PSADT as a biomarker of disease progression in active surveillance.
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON;
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Chiang
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON;
authors.forename: D Andrew
authors.initials: DA
authors.lastname: Loblaw
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON;
authors.forename: Vibhuti
authors.initials: V
authors.lastname: Jethava
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON;
authors.forename: Perakaa
authors.initials: P
authors.lastname: Sethukavalan
authors.affiliation: Department of Biostatistics, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON;
authors.forename: Liying
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON;
authors.forename: Danny
authors.initials: D
authors.lastname: Vesprini
authors.affiliation: Department of Clinical Trials and Epidemiology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON;
authors.forename: Alexandre
authors.initials: A
authors.lastname: Mamedov
authors.affiliation: Division of Urology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON.
authors.forename: Robert
authors.initials: R
authors.lastname: Nam
authors.affiliation: Division of Urology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON.
authors.forename: Laurence
authors.initials: L
authors.lastname: Klotz