title: Does local recurrence of prostate cancer after radiation therapy occur at the site of primary tumor? Results of a longitudinal MRI and MRSI study.
abstract: OBJECTIVE
  To determine if local recurrence of prostate cancer after radiation therapy occurs at the same site as the primary tumor before treatment, using longitudinal magnetic resonance (MR) imaging and MR spectroscopic imaging to assess dominant tumor location.
  
  
  METHODS
  This retrospective study was HIPAA compliant and approved by our Committee on Human Research. We identified all patients in our institutional prostate cancer database (1996 onward) who underwent endorectal MR imaging and MR spectroscopic imaging before radiotherapy for biopsy-proven prostate cancer and again at least 2 years after radiotherapy (n = 124). Two radiologists recorded the presence, location, and size of unequivocal dominant tumor on pre- and postradiotherapy scans. Recurrent tumor was considered to be at the same location as the baseline tumor if at least 50% of the tumor location overlapped. Clinical and biopsy data were collected from all patients.
  
  
  RESULTS
  Nine patients had unequivocal dominant tumor on both pre- and postradiotherapy imaging, with mean pre- and postradiotherapy dominant tumor diameters of 1.8 cm (range, 1-2.2) and 1.9 cm (range, 1.4-2.6), respectively. The median follow-up interval was 7.3 years (range, 2.7-10.8). Dominant recurrent tumor was at the same location as dominant baseline tumor in 8 of 9 patients (89%).
  
  
  CONCLUSIONS
  Local recurrence of prostate cancer after radiation usually occurs at the same site as the dominant primary tumor at baseline, suggesting supplementary focal therapy aimed at enhancing local tumor control would be a rational addition to management.
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California San Francisco, California, USA.
authors.forename: Elnasif
authors.initials: E
authors.lastname: Arrayeh
authors.forename: Antonio C
authors.initials: AC
authors.lastname: Westphalen
authors.forename: John
authors.initials: J
authors.lastname: Kurhanewicz
authors.forename: Mack
authors.initials: M
authors.lastname: Roach
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Jung
authors.forename: Peter R
authors.initials: PR
authors.lastname: Carroll
authors.forename: Fergus V
authors.initials: FV
authors.lastname: Coakley
mesh_terms: D000368:Aged; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D047368:Tumor Burden