title: The role of serial free/total prostate-specific antigen ratios in a watchful observation protocol for men with localized prostate cancer.
abstract: OBJECTIVE
  To examine the change in the free/total prostate specific antigen ratio (f/tPSA) with time and to assess the potential value of serial measurements of f/tPSA as a determinant of disease progression in untreated, low-to-intermediate grade prostate cancer (T1b-T2b N0M0, Gleason score < or = 7 and PSA < or = 15 ng/mL).
  
  
  METHODS
  In a prospective single-arm cohort study from November 1995, patients were conservatively managed with watchful observation alone unless they met arbitrarily defined criteria (clinical, histological and biochemical) of disease progression. Patients were followed regularly and underwent blood tests including PSA and f/tPSA. The initial and mean f/tPSA and the rate of change of f/tPSA with time were evaluated against the rate constant for the PSA doubling time (PSATd). Correlation analyses were used to evaluate any association between baseline clinical variables and either the rate of change of f/tPSA or initial f/tPSA.
  
  
  RESULTS
  As of December 2000, 161 of a total of 206 accrued patients had three or more f/tPSA measurements and formed the basis of the study (median age 70 years; median follow-up 2.7 years). The median initial f/tPSA was 0.16; there was a significant negative correlation between this value and the initial total PSA. The mean f/tPSA and rate of change of f/tPSA with time were significantly negatively correlated with the rate constant for PSATd. Also, the rate of change of f/tPSA correlated negatively with clinical T stage, but not with other baseline variables, including initial PSA, age and Gleason score.
  
  
  CONCLUSIONS
  The f/tPSA in men with untreated, clinically localized prostate cancer varied widely. The negative correlation between the rate of change of f/tPSA with time and rate constant for PSATd suggests that both might provide valuable information to allow clinicians to develop a strategy for optimizing the timing of therapeutic intervention for those patients choosing watchful observation alone.
authors.affiliation: Dept. of Radiation Oncology, Toronto-Sunnybrook Regional Cancer Centre, University of Toronto, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada.
authors.forename: V
authors.initials: V
authors.lastname: Do
authors.forename: R
authors.initials: R
authors.lastname: Choo
authors.forename: G
authors.initials: G
authors.lastname: De Boer
authors.forename: L
authors.initials: L
authors.lastname: Klotz
authors.forename: C
authors.initials: C
authors.lastname: Danjoux
authors.forename: G
authors.initials: G
authors.lastname: Morton
authors.forename: E
authors.initials: E
authors.lastname: Szumacher
authors.forename: N
authors.initials: N
authors.lastname: Fleshner
authors.forename: P
authors.initials: P
authors.lastname: Bunting
mesh_terms: D000230:Adenocarcinoma / Q000097:blood*; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D018572:Disease-Free Survival; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood*; D012044:Regression Analysis
chemical_list: D017430:Prostate-Specific Antigen