title: Postradiotherapy 2-year prostate-specific antigen nadir as a predictor of long-term prostate cancer mortality.
abstract: OBJECTIVE
  To report the influence of posttreatment prostate-specific antigen (PSA) nadir response at 2 years after external beam radiotherapy (RT) on distant metastases (DM) and cause-specific mortality (CSM).
  
  
  METHODS
  Eight hundred forty-four patients with localized prostate cancer were treated with conformal RT. The median duration of follow-up was 9.1 years. A fixed landmark time point at 2 years was used to assess the influence of nadir PSA value as a time-dependent variable on long-term outcomes.
  
  
  RESULTS
  Multivariate analysis demonstrated that nadir PSA <or=1.5 ng/mL at the landmark was an independent predictor of progression-free survival after adjusting for T stage, Gleason score, pre-RT PSA value, and RT dose (p = 0.03). The 5- and 10-year cumulative incidences of DM were 2.4% and 7.9%, respectively, in those with nadir PSA levels <or=1.5 ng/mL at the 2-year landmark, and were 10.3% and 17.5%, respectively, in patients with higher nadir values. Multivariate analysis showed that the higher nadir PSA value at the 2-year landmark (p = 0.002), higher Gleason scores (p < 0.001), and increasing T stage (p = 0.03) were predictors of DM after adjusting for pre-RT PSA values and RT dose. Multivariate analysis also showed that higher Gleason scores (p = 0.002), and higher nadir PSA values at the 2-year landmark (p = 0.03) were risk factors associated with CSM after adjusting for T stage and pre-RT PSA value.
  
  
  CONCLUSIONS
  Nadir PSA values of <or=1.5 ng/mL at 2 years after RT for prostate cancer predict for long-term DM and CSM outcomes. Patients with higher absolute nadir levels at 2 years after treatment should be evaluated for the presence of nonresponding disease, and earlier salvage treatment interventions should be considered.
authors.affiliation: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA. zelefskm@mskcc.org
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zelefsky
authors.forename: Weiji
authors.initials: W
authors.lastname: Shi
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Yamada
authors.forename: Marisa A
authors.initials: MA
authors.lastname: Kollmeier
authors.forename: Brett
authors.initials: B
authors.lastname: Cox
authors.forename: Jessica
authors.initials: J
authors.lastname: Park
authors.forename: Venkatraman E
authors.initials: VE
authors.lastname: Seshan
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002423:Cause of Death; D018572:Disease-Free Survival; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000401:mortality* / Q000473:pathology / Q000532:radiotherapy; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal; D050397:Radiotherapy, Intensity-Modulated; D012307:Risk Factors; D013997:Time Factors
chemical_list: D017430:Prostate-Specific Antigen