title: Prostate-specific antigen as a predictor of radiotherapy response and patterns of failure in localized prostate cancer.
abstract: OBJECTIVE
  A study of preradiation and postradiation, serial serum prostate-specific antigen (PSA) levels was performed in patients who had clinically localized prostate cancer. The prognostic value of the PSA in pretreatment evaluation and posttreatment follow-up was assessed.
  
  
  METHODS
  Sixty-three patients who presented with clinically localized prostate cancer and who were treated with external-beam radiation therapy were followed-up for a median of 25 months. A serum PSA and physical examination were performed at 3-month intervals, and a bone scan was done yearly. An increase in PSA triggered an additional metastatic workup. Prostate rebiopsy was performed for new, palpable nodules or for a serial increase in PSA in the context of a negative metastatic workup.
  
  
  RESULTS
  Forty-one patients remained recurrence-free and 22 recurred clinically, 15 distantly and seven locally. The PSA was the strongest, independent, pretreatment prognostic indicator (P = .019) among pretreatment PSA, stage, and grade, but lost significance when the serum prostatic acid phosphatase (PAP) status was included. The initial rate of the PSA decrease after radiation (median half-life, 2.6 months) failed to predict outcome. Recurrence-free patients reached postradiation PSA levels that were equivalent to those reported in disease-free male populations; failure of the PSA to reach such normal levels was a multivariate predictor of subsequent failure (P less than .037). All clinicopathologic documentations of failure were preceded by an increase in PSA levels during follow-up. Delayed versus early PSA increase was associated with clinically localized versus metastatic first recurrence.
  
  
  CONCLUSIONS
  The serum PSA is an independent pretreatment and posttreatment predictor of outcome. Additionally, for a median follow-up of 25 months, delayed PSA failure is associated with clinically localized rather than metastatic recurrence, a relationship that may help in selection for local salvage therapy.
authors.affiliation: Department of Human Oncology, University of Wisconsin Medical School, Madison.
authors.forename: M A
authors.initials: MA
authors.lastname: Ritter
authors.forename: E M
authors.initials: EM
authors.lastname: Messing
authors.forename: T G
authors.initials: TG
authors.lastname: Shanahan
authors.forename: S
authors.initials: S
authors.lastname: Potts
authors.forename: R J
authors.initials: RJ
authors.lastname: Chappell
authors.forename: T J
authors.initials: TJ
authors.lastname: Kinsella
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000951:Antigens, Neoplasm / Q000097:blood*; D014408:Biomarkers, Tumor / Q000097:blood*; D006801:Humans; D016018:Least-Squares Analysis; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D017430:Prostate-Specific Antigen; D011471:Prostatic Neoplasms / Q000276:immunology / Q000473:pathology / Q000532:radiotherapy*; D012008:Recurrence; D016896:Treatment Outcome
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D017430:Prostate-Specific Antigen