title: Improving prostate brachytherapy quality assurance with MRI-CT fusion-based sector analysis in a phase II prospective trial of men with intermediate-risk prostate cancer.
abstract: OBJECTIVE
  We combined sector analysis with MRI-CT fusion to comprehensively assess postimplant dosimetry after prostate brachytherapy.
  
  
  METHODS
  Subjects were 50 men with intermediate-risk prostate cancer treated with (125)I brachytherapy in a prospective phase II clinical trial. On Day 30 after the implantation, dosimetry was evaluated in the prostate base, midgland, and apex regions on fused MRI-CT scans and CT scans. Volumes of each sector receiving 100% of the prescribed dose (V100) and doses to 90% of each sector (D90) were also calculated on the ultrasonogram used for treatment planning and compared with values derived from CT and fused MRI-CT scans.
  
  
  RESULTS
  Fused MRI-CT scans revealed lower-than-expected doses for the whole prostate (V100=91.3%, D90=152.9Gy) compared with CT scans (98.5% and 183.6Gy, p<0.0001) and lower doses to the prostate base (V100=79%, D90=130Gy) vs. CT (96% and 170Gy, p<0.0001). However, lower doses to the prostate base did not adversely affect biochemical outcomes in men with biopsy-proven disease at the base. At a median followup time of 42 months, the mean prostate-specific antigen level for all patients was 0.3ng/mL, and no patient had experienced biochemical or clinical progression or recurrence.
  
  
  CONCLUSIONS
  MRI-CT fusion-based sector analysis was feasible and revealed significantly lower doses to the prostate base than doses estimated from CT alone, although this did not affect biochemical outcomes. MRI-CT fusion-based sector analysis may be useful for developing MRI-based dosimetric markers to predict disease outcomes and treatment-related morbidity.
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX.
authors: Aaron P
authors: AP
authors: Brown
authors: Thomas J
authors: TJ
authors: Pugh
authors: David A
authors: DA
authors: Swanson
authors: Rajat J
authors: RJ
authors: Kudchadker
authors: Teresa L
authors: TL
authors: Bruno
authors: Eva N
authors: EN
authors: Christensen
authors: Marco
authors: M
authors: van Vulpen
authors: Steven J
authors: SJ
authors: Frank
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D001918:Brachytherapy / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D009367:Neoplasm Staging; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011874:Radiometry / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Brachytherapy; Prostate cancer; Sector analysis