title: Dosimetry of an extracapsular anulus following permanent prostate brachytherapy.
abstract: OBJECTIVE
  Recent studies have suggested that extracapsular brachytherapy treatment margins correlate with biochemical control. It is likely that volumetric geographic dosimetric parameters will be more robust than selected radial measurements. Accordingly, we evaluated extracapsular volumetric dosimetric parameters in low-risk patients.
  
  
  METHODS
  A total of 263 low-risk prostate cancer patients randomized to Pd-103 versus I-125 were implanted with a brachytherapy target volume consisting of the prostate with a 5-mm periprostatic margin. The median follow-up was 4.2 years. All patients were implanted at least 3 years prior to analysis. Within 2 hours of implantation, an axial CT was obtained for postimplant dosimetry. A 5-mm three-dimensional periprostatic anulus was constructed around the prostate and evaluated in its entirety and in 90 degrees segments. Prostate and anular dosimetric parameters consisted of V100/V150/V200 and D90. Biochemical progression-free survival (bPFS) was defined as a PSA < or =0.50 ng/mL after nadir.
  
  
  RESULTS
  The Pd-103 and I-125 arms were well-matched in terms of clinical, biochemical, and pathologic presentation. Six-year bPFS was 96.8% versus 99.2% for I-125 versus Pd-103 (P = 0.149). The most recent median posttreatment PSA was <0.04 ng/mL for both isotopes. No significant differences in postoperative anular doses were discerned between bPFS and failed patients.
  
  
  CONCLUSIONS
  A postimplant 5-mm, three-dimensional periprostatic anulus provides substantial information regarding dosimetric coverage. However, with a median follow-up of 4.2 years, such volumetric and geographic parameters have not proven useful in predicting biochemical outcome in low-risk patients.
authors.affiliation: Schiffler Cancer Center, Wheeling Jesuit University, Wheeling, WV, USA. gmerrick@urologicresearchinstitute.org
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Merrick
authors.forename: Wayne M
authors.initials: WM
authors.lastname: Butler
authors.forename: Kent E
authors.initials: KE
authors.lastname: Wallner
authors.forename: Zachariah A
authors.initials: ZA
authors.lastname: Allen
authors.forename: Brian
authors.initials: B
authors.lastname: Kurko
authors.forename: Richard L
authors.initials: RL
authors.lastname: Anderson
authors.forename: Robert
authors.initials: R
authors.lastname: Grammer
authors.forename: Robert W
authors.initials: RW
authors.lastname: Galbreath
authors.forename: Lawrence
authors.initials: L
authors.lastname: True
authors.forename: Edward
authors.initials: E
authors.lastname: Adamovich
mesh_terms: D001918:Brachytherapy; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage*; D008297:Male; D010165:Palladium / Q000008:administration & dosage*; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011829:Radiation Dosage; D011868:Radioisotopes / Q000008:administration & dosage*
chemical_list: D007457:Iodine Radioisotopes; D011868:Radioisotopes; D010165:Palladium