title: Salvage radiotherapy for rising prostate-specific antigen levels after radical prostatectomy for prostate cancer: dose-response analysis.
abstract: OBJECTIVE
  To investigate the association between external beam radiotherapy (EBRT) dose and biochemical failure (BcF) of prostate cancer in patients who received salvage prostate bed EBRT for a rising prostate-specific antigen (PSA) level after radical prostatectomy.
  
  
  METHODS
  We evaluated patients with a rising PSA level after prostatectomy who received salvage EBRT between July 1987 and October 2007. Patients receiving pre-EBRT androgen suppression were excluded. Cox proportional hazards models were used to investigate the association between EBRT dose and BcF. Dose was considered as a numeric variable and as a categoric variable (low, <64.8 Gy; moderate, 64.8-66.6 Gy; high, >66.6 Gy).
  
  
  RESULTS
  A total of 364 men met study selection criteria and were followed up for a median of 6.0 years (range, 0.1-19.3 years). Median pre-EBRT PSA level was 0.6 ng/mL. The estimated cumulative rate of BcF at 5 years after EBRT was 50% overall and 57%, 46%, and 39% for the low-, moderate-, and high-dose groups, respectively. In multivariable analysis adjusting for potentially confounding variables, there was evidence of a linear trend between dose and BcF, with risk of BcF decreasing as dose increased (relative risk [RR], 0.77 [5.0-Gy increase]; p = 0.05). Compared with the low-dose group, there was evidence of a decreased risk of BcF for the high-dose group (RR, 0.60; p = 0.04), but no difference for the moderate-dose group (RR, 0.85; p = 0.41).
  
  
  CONCLUSIONS
  Our results suggest a dose response for salvage EBRT. Doses higher than 66.6 Gy result in decreased risk of BcF.
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Jacksonville, FL 32224, USA.
authors.forename: Johnny Ray
authors.initials: JR
authors.lastname: Bernard
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Buskirk
authors.forename: Michael G
authors.initials: MG
authors.lastname: Heckman
authors.forename: Nancy N
authors.initials: NN
authors.lastname: Diehl
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Ko
authors.forename: Orlan K
authors.initials: OK
authors.lastname: Macdonald
authors.forename: Steven E
authors.initials: SE
authors.lastname: Schild
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Pisansky
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004307:Dose-Response Relationship, Radiation; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016016:Proportional Hazards Models; D017430:Prostate-Specific Antigen / Q000097:blood*; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000097:blood* / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D016879:Salvage Therapy / Q000379:methods*; D013997:Time Factors
chemical_list: D017430:Prostate-Specific Antigen