title: Prostate-specific antigen at 4 to 5 years after low-dose-rate prostate brachytherapy is a strong predictor of disease-free survival.
abstract: OBJECTIVE
  To determine (1) the prognostic utility of prostate-specific antigen (PSA) concentration at 45 to 60 months (48mPSA) after low-dose-rate prostate brachytherapy (LDR-PB); (2) the predictors of 48mPSA; and (3) the prognostic utility of directional trends between PSA levels at 24, 36, and 48 months after LDR-PB.
  
  
  METHODS
  Between 1998 and 2008, 2223 patients with low- and intermediate-risk prostate cancer received LDR-PB monotherapy. A cohort of 1434 of these patients was identified with a documented 48mPSA and no evidence of disease relapse prior to the 48mPSA. In addition, a subset of this cohort (n=585) was identified with ≥72 months of follow-up and documented PSA values at both 24 and 36 months after implantation.
  
  
  RESULTS
  Median follow-up time was 76 months. Eight-year Kaplan-Meier disease-free survival (DFS) rates were 100% vs 73.4% for patients with 48mPSA≤0.2 vs those with >0.2 ng/mL; 99.1% versus 53.8% for a 48mPSA threshold of ≤0.4 versus >0.4 ng/mL, respectively; and 97.3% versus 0% for a threshold of ≤1.0 versus >1.0 ng/mL, respectively. On multivariate analysis, the only factor predictive of DFS was 48mPSA (P<.0001). On subset analysis (n=585), 29 patients had a PSA rise (defined as >0.2 ng/mL) between 24 and 36 months, 24 patients had a rise between 36 and 48 months, and 11 patients had rises over both intervals. Failure rates in these patients were 52%, 79%, and 100%, respectively. On multivariate analysis, initial PSA, androgen deprivation therapy, and dose to 90% of the prostate significantly correlated with 48mPSA but together accounted for only ∼5% of its total variance.
  
  
  CONCLUSIONS
  The 48mPSA after LDR-PB is highly predictive of long-term DFS. Patients with 48mPSA≤0.4 ng/mL had a <1% risk of disease relapse at 8 years, whereas all patients with 48mPSA>1.0 ng/mL relapsed. Consecutive PSA rises of >0.2 ng/mL from 24 to 36 months and from 36 to 48 months were also highly predictive of subsequent failure.
authors: Department of Radiation Oncology, British Columbia Cancer Agency Vancouver Centre, Vancouver, British Columbia, Canada; Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Andrea C
authors: AC
authors: Lo
authors: Department of Radiation Oncology, British Columbia Cancer Agency Vancouver Centre, Vancouver, British Columbia, Canada; Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address: JMorris@bccancer.bc.ca.
authors: W James
authors: WJ
authors: Morris
authors: Department of Medical Physics, British Columbia Cancer Agency Vancouver Centre, Vancouver, British Columbia, Canada.
authors: Vincent
authors: V
authors: Lapointe
authors: Department of Population Oncology, British Columbia Cancer Agency Vancouver Centre, Vancouver, British Columbia, Canada.
authors: Jeremy
authors: J
authors: Hamm
authors: Department of Radiation Oncology, British Columbia Cancer Agency Vancouver Centre, Vancouver, British Columbia, Canada; Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Mira
authors: M
authors: Keyes
authors: Department of Radiation Oncology, British Columbia Cancer Agency Vancouver Centre, Vancouver, British Columbia, Canada; Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Tom
authors: T
authors: Pickles
authors: Department of Radiation Oncology, British Columbia Cancer Agency Vancouver Centre, Vancouver, British Columbia, Canada; Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Michael
authors: M
authors: McKenzie
authors: Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Department of Medical Physics, British Columbia Cancer Agency Vancouver Centre, Vancouver, British Columbia, Canada.
authors: Ingrid
authors: I
authors: Spadinger
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001918:Brachytherapy / Q000379:methods* / Q000401:mortality; D018572:Disease-Free Survival; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000097:blood / Q000401:mortality; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood / Q000401:mortality / Q000532:radiotherapy*; D012372:ROC Curve; D011879:Radiotherapy Dosage; D013739:Testosterone / Q000097:blood; D013997:Time Factors
chemical_list: D013739:Testosterone; D017430:Prostate-Specific Antigen