title: Predicting biochemical failure and overall survival through intratherapy PSA changes during definitive external beam radiotherapy.
abstract: OBJECTIVE
  To determine whether intratherapy prostate-specific antigen (itPSA) changes during radiotherapy (RT) predict prostate cancer outcomes.
  
  
  METHODS
  We retrospectively identified patients treated with definitive external beam RT without hormonal therapy who had at least two itPSA measurements. We calculated the adjusted ratio of rise (ARR) in itPSA relative to the pretreatment baseline PSA for each patient. This was defined as ln(maximal itPSA + 1)/ln(baseline PSA + 1). We stratified patients according to an ARR of <1 vs. >1.1. This corresponded to an approximately <30% vs. >30% increase in PSA during RT. Univariate and multivariate analyses were performed examining for biochemical failure-free survival (BFFS) and overall survival (OS).
  
  
  RESULTS
  At a median follow-up of 74 months, we identified 307 patients who met our criteria. Univariate analysis revealed that patients with an ARR of <1.1 (n = 182) had statistically significant inferior BFFS and OS compared with those with an ARR of >1.1 (n = 125). The median BFFS and OS for these two groups was 51 vs. 101 months (p = 0.001) and 96 vs. 128 months (p = 0.01), respectively. On multivariate analysis, the effect of ARR on the risk of biochemical failure for patients with an ARR of <1.1 was significant (p = 0.03) only during the first year after RT. In contrast, the effect of the ARR on OS remained significant for a full 5 years (p = 0.05).
  
  
  CONCLUSIONS
  The results of our study have shown that an ARR of <1.1 predicts for inferior BFFS and OS in patients treated with RT alone. PSA measurement during RT is a novel clinical tool that could be used to identify patients who might warrant more aggressive therapeutic intervention.
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Soto
authors.forename: Rebecca R
authors.initials: RR
authors.lastname: Andridge
authors.forename: Jeremy M G
authors.initials: JM
authors.lastname: Taylor
authors.forename: Patrick W
authors.initials: PW
authors.lastname: McLaughlin
authors.forename: Howard M
authors.initials: HM
authors.lastname: Sandler
authors.forename: Charlie C
authors.initials: CC
authors.lastname: Pan
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D018572:Disease-Free Survival; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D012189:Retrospective Studies; D016019:Survival Analysis; D017741:Survivors; D017211:Treatment Failure; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; D017430:Prostate-Specific Antigen