title: The importance of an exponential prostate-specific antigen decline after external beam radiotherapy for intermediate risk prostate cancer.
abstract: BACKGROUND
  To study the influence of an exponential prostate-specific antigen (PSA) decline on biochemical failure after external-beam radiotherapy (EBRT).
  
  
  METHODS
  We analyzed 114 patients with intermediate risk prostate cancer (Gleason≤6 and PSA 10-20 or Gleason 7 and PSA <10). Patients were randomized between EBRT doses of either 70.2 Gy or 79.2 Gy (1.8 Gy per day). All patients had a follow up of at least six PSA measurements post-EBRT. Exponential decline and PSA half life were included in a Cox regression analysis for factors associated with biochemical failure.
  
  
  RESULTS
  A total of 80/114 (70.2%) patterns were classified as having an exponential PSA decline. Both exponential decline (HR 0.115, 95%CI 0.03-0.44, p=0.0016) and PSA half life ratio were statistically significant predictors (HR 1.03 (95% CI 1.01-1.06)) of biochemical failure. In the model predicting for exponential decline, none of the factors were significant.
  
  
  CONCLUSIONS
  Patients with an exponential PSA decline show a better biochemical outcome in the long term.
authors.affiliation: Department of Radiation Oncology, Centre hospitalier de l'Université de Montréal, Québec, Canada.
authors.forename: Guila
authors.initials: G
authors.lastname: Delouya
authors.forename: Gabriel
authors.initials: G
authors.lastname: Kaufman
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Sylvestre
authors.forename: Thu-Van
authors.initials: TV
authors.lastname: Nguyen
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Bahary
authors.forename: Daniel
authors.initials: D
authors.lastname: Taussky
authors.forename: Philippe
authors.initials: P
authors.lastname: Després
mesh_terms: D000368:Aged; D006801:Humans; D008297:Male; D060787:Neoplasm Grading; D009364:Neoplasm Recurrence, Local / Q000097:blood; D016016:Proportional Hazards Models; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000532:radiotherapy*; D011879:Radiotherapy Dosage
chemical_list: D017430:Prostate-Specific Antigen