title: Effect of post-implant edema on prostate brachytherapy treatment margins.
abstract: OBJECTIVE
  To determine if postimplant prostate brachytherapy treatment margins calculated on Day 0 differ substantially from those calculated on Day 30.
  
  
  METHODS
  Thirty patients with 1997 American Joint Commission on Cancer clinical stage T1-T2 prostatic carcinoma underwent prostate brachytherapy with I-125 prescribed to 144 Gy. Treatment planning methods included using loose seeds in a modified peripheral loading pattern and treatment margins (TMs) of 5-8 mm. Postimplant plain radiographs, computed tomography scans, and magnetic resonance scans were obtained 1-4 hours after implantation (Day 0). A second set of imaging studies was obtained at 30 days after implantation (Day 30) and similarly analyzed. Treatment margins were measured as the radial distance in millimeters from the prostate edge to the 100% isodose line. The TMs were measured and tabulated at 90 degrees intervals around the prostate periphery at 0.6-cm intervals. Each direction was averaged to obtain the mean anterior, posterior, left, and right margins.
  
  
  RESULTS
  The mean overall TM increased from 2.6 mm (+/-2.3) on Day 0 to 3.5 mm (+/-2.4) on Day 30. The mean anterior margin increased from 1.2 mm on Day 0 to 1.8 mm on Day 30. The posterior margin increased from 1.2 mm on Day 0 to 2.8 mm on Day 30. The lateral treatment margins increased most over time, with mean right treatment margin increasing from 3.9 mm on Day 0 to 4.7 mm on Day 30.
  
  
  CONCLUSIONS
  Treatment margins appear to be durable in the postimplant period, with a clinically insignificant increase from Day 0 to Day 30.
authors.affiliation: Radiation Oncology, Arizona Oncology Services, Phoenix, AZ 85260, USA.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Reed
authors.forename: Kent
authors.initials: K
authors.lastname: Wallner
authors.forename: Eric
authors.initials: E
authors.lastname: Ford
authors.forename: Amy
authors.initials: A
authors.lastname: Mueller
authors.forename: Gregory
authors.initials: G
authors.lastname: Merrick
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Maki
authors.forename: Steven
authors.initials: S
authors.lastname: Sutlief
authors.forename: Wayne
authors.initials: W
authors.lastname: Butler
mesh_terms: D001918:Brachytherapy / Q000009:adverse effects*; D004487:Edema / Q000209:etiology / Q000473:pathology*; D006801:Humans; D008297:Male; D011467:Prostate / Q000473:pathology; D011469:Prostatic Diseases / Q000209:etiology / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage