title: Interval to biochemical failure highly prognostic for distant metastasis and prostate cancer-specific mortality after radiotherapy.
abstract: OBJECTIVE
  Few biochemical parameters have been related to mortality. The present study examined the clinical utility of the interval to biochemical failure (IBF) as a prognostic factor for distant metastasis (DM) and prostate cancer-specific mortality (PCSM) after radiotherapy.
  
  
  METHODS
  The study group consisted of 211 T1c-T3Nx-N0M0 patients who had experienced BF among 1,174 men treated with three-dimensional conformal radiotherapy alone. Biochemical failure was defined as a post-treatment prostate-specific antigen (PSA) level of at, or greater than, the PSA nadir plus 2 ng/mL. Cox proportional hazards modeling was used to identify independent predictors of DM and PCSM on multivariate analysis.
  
  
  RESULTS
  An IBF of <18 months was independently predictive for DM (p = 0.008), as was a Gleason score of 7-10 (p = 0.0005), PSA nadir >or=2 ng/mL (p = 0.04), and decreasing radiation dose (p = 0.02) on multivariate analysis, including increasing pretreatment PSA level, PSA nadir >or=2.5 ng/mL, PSA doubling time of <3 months, and Stage T3 disease. An IBF of <18 months was the only predictor of PCSM (p = 0.0003) in the same model. The actuarial 5-year DM rate for an IBF of <18 vs. >or=18 months was 52% vs. 20% (p < 0.0001), and the actuarial PCSM rate was 36% vs. 6%, respectively (p = 0.0001).
  
  
  CONCLUSIONS
  The IBF is an important descriptor of the PSA kinetics after radiotherapy to identify men at high risk of clinical failure and death. A IBF of <18 months could aid in selecting men for early, aggressive salvage therapy or participation in a clinical trial.
authors.affiliation: Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA 19111, USA. mark.buyyounouski@fccc.edu
authors.forename: Mark K
authors.initials: MK
authors.lastname: Buyyounouski
authors.forename: Alexandra L
authors.initials: AL
authors.lastname: Hanlon
authors.forename: Eric M
authors.initials: EM
authors.lastname: Horwitz
authors.forename: Alan
authors.initials: A
authors.lastname: Pollack
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D016016:Proportional Hazards Models; D011471:Prostatic Neoplasms / Q000097:blood / Q000473:pathology / Q000532:radiotherapy*; D020266:Radiotherapy, Conformal; D013997:Time Factors; D017211:Treatment Failure