title: Conditional probability of reclassification in an active surveillance program for prostate cancer.
abstract: OBJECTIVE
  We evaluated the risk of prostate cancer reclassification by time on active surveillance.
  
  
  METHODS
  From 1995 to 2014 we evaluated 557 and 251 men at very low and at low risk, respectively, who were on active surveillance and compliant with prostate biopsies. Our primary study outcome was reclassification to higher risk disease by grade or extent. Freedom from reclassification was estimated using the Kaplan-Meier approach with adjustment for covariates using the Cox proportional hazards model.
  
  
  RESULTS
  Within the first 2 years of surveillance patient survival free of reclassification by grade (p = 0.20) and by any biopsy criteria (p = 0.25) was similar in men with very low and low risk disease. After 2 years men with low risk disease were 2.4 times more likely to be diagnosed with a Gleason score of greater than 6 than men with very low risk disease (p = 0.002, HR 2.4, 95% CI 1.9-3.5). Additionally, beyond 2 years on surveillance the risk of lifetime reclassification by grade and by any criteria decreased by 30% and 35% (each p <0.0001, HR 0.70, 95% CI 0.60-0.76 and HR 0.65, 95% CI 0.57-0.72, respectively) with each biopsy that showed no reclassification.
  
  
  CONCLUSIONS
  The reclassification rate during surveillance is not equally distributed across time or risk groups. Due to misclassification at diagnosis the reclassification rate in very low and low risk groups is similar in the first 2 years but differs significantly beyond 2 years. The risk of reclassification decreases with time for each nonreclassifying biopsy beyond 2 years.
authors.affiliation: The James Buchanan Brady Urological Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Ridwan
authors.initials: R
authors.lastname: Alam
authors.affiliation: The James Buchanan Brady Urological Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: H Ballentine
authors.initials: HB
authors.lastname: Carter
authors.affiliation: The James Buchanan Brady Urological Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Patricia
authors.initials: P
authors.lastname: Landis
authors.affiliation: The James Buchanan Brady Urological Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Jonathan I
authors.initials: JI
authors.lastname: Epstein
authors.affiliation: The James Buchanan Brady Urological Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland. Electronic address: mmamawa1@jhmi.edu.
authors.forename: Mufaddal
authors.initials: M
authors.lastname: Mamawala
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000628:therapy*; D018570:Risk Assessment; D057832:Watchful Waiting / Q000145:classification*
keywords: classification; diagnosis; prostate-specific antigen; prostatic neoplasms; risk