title: Percent positive biopsy cores as a prognostic factor for prostate cancer treated with external beam radiation.
abstract: OBJECTIVE
  To examine the prognostic value of percent positive cores (PPC) in prostate cancer patients treated with external beam radiotherapy (RT).
  
  
  METHODS
  An institutional review board-approved, retrospective analysis was conducted on 814 patients treated with RT with or without hormonal therapy between 1984 and 2002. Percent positive cores (number of positive cores divided by total number of cores) was calculable for 591 patients with a median follow-up of 65 months. Univariate and multivariable analyses were performed using Kaplan-Meier and Cox proportional hazard methods relating PPC to other risk factors, biochemical/clinical disease-free survival (PSA-DFS), prostate cancer-specific survival (DSS), and overall survival (OS).
  
  
  RESULTS
  Percent positive cores was associated with stage, Gleason score (GS), pretreatment serum prostate-specific antigen (PSA) level, and use of adjunctive androgen suppression therapy. The 5-year PSA-DFS, DSS, and OS rates were 80%, 99%, and 91%, respectively, for patients with PPC less than 50%, compared with 56%, 94%, and 87% for patients with PPC 50% or greater (P <0.0001, <0.004, and <0.04, respectively). Multivariable analysis revealed that PPC, stage, GS, PSA, and androgen suppression therapy were all significantly associated with PSA-DFS, whereas only GS was associated with DSS and OS. For high, intermediate, and low-risk patients, 5-year PSA-DFS was 62% versus 39%, 80% versus 59%, and 90% versus 82% for PPC less than 50% versus PPC 50% or greater, respectively.
  
  
  CONCLUSIONS
  Percent positive cores predicts outcome of prostate cancer patients treated with RT, independently of other known prognostic factors. Percent positive cores may have particular use for further risk stratification within established clinical risk categories.
authors.affiliation: Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA. spalda@med.umich.edu
authors.forename: Aaron C
authors.initials: AC
authors.lastname: Spalding
authors.forename: Stephanie
authors.initials: S
authors.lastname: Daignault
authors.forename: Howard M
authors.initials: HM
authors.lastname: Sandler
authors.forename: Rajal B
authors.initials: RB
authors.lastname: Shah
authors.forename: Charlie C
authors.initials: CC
authors.lastname: Pan
authors.forename: Michael E
authors.initials: ME
authors.lastname: Ray
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001707:Biopsy, Needle / Q000379:methods*; D001918:Brachytherapy; D019583:Dose Fractionation, Radiation; D006801:Humans; D008297:Male; D008875:Middle Aged; D011336:Probability; D011379:Prognosis; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000401:mortality / Q000473:pathology* / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D018570:Risk Assessment; D016019:Survival Analysis; D016896:Treatment Outcome
chemical_list: D017430:Prostate-Specific Antigen