title: What does postradiotherapy PSA nadir tell us about freedom from PSA failure and progression-free survival in patients with low and intermediate-risk localized prostate cancer?
abstract: OBJECTIVE
  To determine whether the post-external beam radiotherapy (RT) prostate-specific antigen nadir (nPSA) improves our ability to predict freedom from PSA failure, progression-free survival (PFS), and overall survival. Controversy regarding the importance of nPSA after external beam RT as a prognostic indicator for patients with localized prostate cancer has continued.
  
  
  METHODS
  This analysis was based on the data from 748 patients with low and intermediate-risk localized prostate cancer treated with external beam RT alone. Patients were categorized by nPSA quartile groups with cutpoints of less than 0.3, 0.3 to less than 0.6, 0.6 to less than 1.2, and 1.2 ng/mL or greater. Both univariate and multivariate analyses were used to determine the significance of nPSA on PSA failure (American Society for Therapeutic Radiology Oncology consensus definition), PFS (death after PSA failure), and overall survival (death from any cause).
  
  
  RESULTS
  Freedom from PSA failure was strongly associated with nadir quartile groups (P <0.0001). PFS was also significantly different statistically among nadir quartile groups (P = 0.02). No statistically significant difference was found in overall survival associated with nPSA at this point.
  
  
  CONCLUSIONS
  nPSA is a strong independent predictor of freedom from PSA failure and PFS in patients with low and intermediate-risk localized prostate cancer treated with RT alone. Longer follow-up and larger patient numbers are required to confirm these observations.
authors.affiliation: Department of Radiation Oncology, University of California, San Francisco, School of Medicine, 94143-1708, USA.
authors.forename: K D
authors.initials: KD
authors.lastname: DeWitt
authors.forename: H M
authors.initials: HM
authors.lastname: Sandler
authors.forename: V
authors.initials: V
authors.lastname: Weinberg
authors.forename: P W
authors.initials: PW
authors.lastname: McLaughlin
authors.forename: M
authors.initials: M
authors.lastname: Roach
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis* / Q000401:mortality / Q000532:radiotherapy*; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D018572:Disease-Free Survival; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009367:Neoplasm Staging; D017430:Prostate-Specific Antigen / Q000032:analysis*; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000401:mortality / Q000532:radiotherapy*; D018570:Risk Assessment; D015996:Survival Rate; D017211:Treatment Failure
chemical_list: D014408:Biomarkers, Tumor; D017430:Prostate-Specific Antigen