title: Increasing external beam dose for T1-T2 prostate cancer: effect on risk groups.
abstract: OBJECTIVE
  The aim of this study was to investigate effect of increasing dose on risk groups for clinical failure (CF: local failure or distant failure or hormone ablation or PSA>or=25 ng/ml) in patients with T1-T2 prostate cancer treated with external beam radiotherapy.
  
  
  METHODS
  Patients (n=4,537) were partitioned into nonoverlapping dose ranges, each narrow enough that dose was not a predictor of CF, and risk groups for CF were determined using recursive partitioning analysis (RPA). The same technique was applied to the highest of these dose ranges (70-76 Gy, 1,136 patients) to compare risk groups for CF in this dose range with the conventional risk-group classification.
  
  
  RESULTS
  Cutpoints defining low-risk groups in each dose range shifted to higher initial PSA levels and Gleason scores with increasing dose. Risk groups for CF in the dose range 70-76 Gy were not consistent with conventional risk groups.
  
  
  CONCLUSIONS
  The conventional classification of risk groups was derived in the early PSA era, when total doses<70 Gy were common, and it is inconsistent with risk groups for patients treated to doses>70 Gy. Risk-group classifications must be continuously re-examined whenever the trend is toward increasing total dose.
authors.affiliation: Department of Biostatistics and Applied Mathematics, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, and Department of Radiation Oncology, William Beaumont Hospital, Deroit, MI, USA. hdt@odin.mdacc.tmc.edu
authors.forename: Howard D
authors.initials: HD
authors.lastname: Thames
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Kuban
authors.forename: Michelle L
authors.initials: ML
authors.lastname: DeSilvio
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: Howard M
authors.initials: HM
authors.lastname: Sandler
authors.forename: William U
authors.initials: WU
authors.lastname: Shipley
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zelefsky
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Zietman
mesh_terms: D006801:Humans; D008297:Male; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D012306:Risk; D017211:Treatment Failure
chemical_list: D017430:Prostate-Specific Antigen