title: Time to metabolic atrophy after permanent prostate seed implantation based on magnetic resonance spectroscopic imaging.
abstract: OBJECTIVE
  To characterize the time to metabolic atrophy (TMA) after permanent prostate implantation (PPI) using combined MRI and magnetic resonance spectroscopic imaging (MRSI) compared with the time to prostate-specific antigen (PSA) nadir.
  
  
  METHODS
  This study was based on a posttreatment analysis comparing the MRI/MRSI findings with the PSA levels of 65 patients treated with PPI alone or combined with external beam radiotherapy and/or HT. The fraction of interpretable voxels demonstrating metabolic atrophy was used to compare the TMA with the time to PSA nadir.
  
  
  RESULTS
  The fraction of patients with metabolic atrophy in >95% of usable voxels after PPI increased from approximately 46% to 100% at 6 and 48 months, respectively. The mean time for PSA nadir vs. TMA was 42.5 vs. 28.9 months (PPI), 32.8 vs. 25.6 months (external beam radiotherapy + PPI), and 25.3 vs. 28.0 months (external beam radiotherapy + hormonal therapy + PPI).
  
  
  CONCLUSIONS
  Magnetic resonance spectroscopic imaging may provide an early tool for evaluating the treatment response for patients treated with PPI. If supported by longer follow-up, TMA may be a useful adjunct to PSA measurement for assessing local control after PPI and could be useful in evaluating the complex relationships between the quality of the implant and the time to indication of successful therapy.
authors.affiliation: Department of Radiation Oncology, University of California, San Francisco, School of Medicine, 94143-1708, USA. pickett@radonc17.ucsf.edu
authors.forename: Barby
authors.initials: B
authors.lastname: Pickett
authors.forename: Randall K
authors.initials: RK
authors.lastname: Ten Haken
authors.forename: John
authors.initials: J
authors.lastname: Kurhanewicz
authors.forename: Aliya
authors.initials: A
authors.lastname: Qayyum
authors.forename: Katsuto
authors.initials: K
authors.lastname: Shinohara
authors.forename: Beverly
authors.initials: B
authors.lastname: Fein
authors.forename: Mack
authors.initials: M
authors.lastname: Roach
mesh_terms: D001918:Brachytherapy; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D017430:Prostate-Specific Antigen / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000532:radiotherapy*; D016896:Treatment Outcome
chemical_list: D017430:Prostate-Specific Antigen