title: Nadir prostate-specific antigen within 12 months after radiotherapy predicts biochemical and distant failure.
abstract: OBJECTIVE
  To determine whether nadir prostate-specific antigen (PSA) levels within 12 months (nadir PSA12) after completion of radiotherapy (RT) can be used as an early marker of recurrence risk.
  
  
  METHODS
  A total of 4839 patients were treated with RT and without hormonal therapy from 1986 to 1995 for Stage T1-T2 prostate cancer at nine institutions. Of these 4839 patients, 4833, with a median follow-up of 6.3 years, met the criteria for analysis. The study endpoints included freedom from PSA failure, initiation of androgen deprivation, or documented local or distant failure (PSA-DFS); freedom from clinically apparent distant metastasis (DMFS); and overall survival (OS).
  
  
  RESULTS
  Patients with a nadir PSA12 of 2.0 ng/mL or less had an 8-year PSA-DFS, DMFS, and OS rate of 55%, 95%, and 73%, respectively, compared with 40%, 88%, and 69%, respectively, for patients with a nadir PSA12 of more than 2.0 ng/mL. Multivariate analysis confirmed that a nadir PSA12 of greater than 2 ng/mL was an independent predictor of PSA-DFS, DMFS, and OS. Classification and regression tree analysis identified the nadir PSA12 levels after RT associated with PSA-DFS, DMFS, and OS. Nadir PSA12, combined with the pretreatment PSA level, identified patients at particularly high risk of distant metastasis.
  
  
  CONCLUSIONS
  The results of this large, multi-institutional study have demonstrated that nadir PSA12 is predictive of clinical outcomes for patients with localized prostate cancer after RT. A high pretreatment PSA level and high nadir PSA12 will identify patients at particularly high risk who might benefit from early adjuvant therapy.
authors.affiliation: Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0010, USA. mray@umich.edu
authors.forename: Michael E
authors.initials: ME
authors.lastname: Ray
authors.forename: Larry B
authors.initials: LB
authors.lastname: Levy
authors.forename: Eric M
authors.initials: EM
authors.lastname: Horwitz
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Kupelian
authors.forename: Alvaro A
authors.initials: AA
authors.lastname: Martinez
authors.forename: Jeff M
authors.initials: JM
authors.lastname: Michalski
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Pisansky
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zelefsky
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Zietman
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Kuban
mesh_terms: D000230:Adenocarcinoma / Q000097:blood* / Q000473:pathology / Q000532:radiotherapy*; D014408:Biomarkers, Tumor / Q000097:blood*; D001706:Biopsy; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000097:blood* / Q000473:pathology; D009367:Neoplasm Staging; D011379:Prognosis; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000473:pathology / Q000532:radiotherapy*; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D017211:Treatment Failure
chemical_list: D014408:Biomarkers, Tumor; D017430:Prostate-Specific Antigen