title: Local control following permanent prostate brachytherapy: effect of high biologically effective dose on biopsy results and oncologic outcomes.
abstract: OBJECTIVE
  To determine factors that influence local control and systemic relapse in patients undergoing permanent prostate brachytherapy (PPB).
  
  
  METHODS
  A total of 584 patients receiving PPB alone or PPB with external beam radiation therapy (19.5%) agreed to undergo prostate biopsy (PB) at 2 years postimplantion and yearly if results were positive or if the prostate-specific antigen (PSA) level increased. Short-term hormone therapy was used with 280 (47.9%) patients. Radiation doses were converted to biologically effective doses (BED) (using alpha/beta = 2). Comparisons were made by chi-square analysis and linear regression. Survival was determined by the Kaplan-Meier method.
  
  
  RESULTS
  The median PSA concentration was 7.1 ng/ml, and the median follow-up period was 7.1 years. PB results were positive for 48/584 (8.2%) patients. Positive biopsy results by BED group were as follows: 22/121 (18.2%) patients received a BED of < or =150 Gy; 15/244 (6.1%) patients received >150 to 200 Gy; and 6/193 (3.1%; p < 0.001) patients received >200 Gy. Significant associations of positive PB results by risk group were low-risk group BED (p = 0.019), intermediate-risk group hormone therapy (p = 0.011) and BED (p = 0.040), and high-risk group BED (p = 0.004). Biochemical freedom from failure rate at 7 years was 82.7%. Biochemical freedom from failure rate by PB result was 84.7% for negative results vs. 59.2% for positive results (p < 0.001). Cox regression analysis revealed significant associations with BED (p = 0.038) and PB results (p = 0.002) in low-risk patients, with BED (p = 0.003) in intermediate-risk patients, and with Gleason score (p = 0.006), PSA level (p < 0.001), and PB result (p = 0.038) in high-risk patients. Fifty-three (9.1%) patients died, of which eight deaths were due to prostate cancer. Cause-specific survival was 99.2% for negative PB results vs. 87.6% for positive PB results (p < 0.001).
  
  
  CONCLUSIONS
  Higher radiation doses are required to achieve local control following PPB. A BED of >200 Gy with an alpha/beta ratio of 2 yields 96.9% local control rate. Failure to establish local control impacts survival.
authors.affiliation: Department of Urology, Mount Sinai School of Medicine, New York, New York, USA. nelsonstone@optonline.net
authors.forename: Nelson N
authors.initials: NN
authors.lastname: Stone
authors.forename: Richard G
authors.initials: RG
authors.lastname: Stock
authors.forename: Jamie A
authors.initials: JA
authors.lastname: Cesaretti
authors.forename: Pam
authors.initials: P
authors.lastname: Unger
mesh_terms: D001706:Biopsy / Q000379:methods; D001918:Brachytherapy / Q000379:methods*; D016009:Chi-Square Distribution; D005500:Follow-Up Studies; D006801:Humans; D016014:Linear Models; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000097:blood / Q000473:pathology; D011467:Prostate / Q000473:pathology; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D012062:Relative Biological Effectiveness; D018084:Ultrasonography, Interventional
chemical_list: D017430:Prostate-Specific Antigen