title: Morphological assessment of the interface between tumor and neighboring tissues, by magnetic resonance imaging, before and after radiotherapy in patients with locally advanced rectal cancer.
abstract: BACKGROUND
  Magnetic resonance imaging (MRI) in rectal cancer is sometimes performed after radiotherapy (MRI 2) to evaluate tumor response and to choose alternative forms of surgery. The accuracy of MRI 2 in distinguishing tumor delineation might be difficult due to fibrosis.
  
  
  OBJECTIVE
  To evaluate the morphological changes in the interface between the tumor and neighboring organs on MRI 2 performed after radiotherapy, and to assess the accuracies of MRI before and after radiotherapy compared to histopathology after surgery.
  
  
  METHODS
  Sixteen patients with locally advanced primary rectal cancer, with MRI before and after radiotherapy, were retrospectively studied, concerning the interface between the tumor and neighboring structures. The accuracies of MRI before and after radiotherapy were compared based on histopathology as a reference.
  
  
  RESULTS
  The accuracies of both MRI before and after radiotherapy were moderate, with no additional value of MRI after radiotherapy compared to MRI before radiotherapy. The most predictive form of interface for involvement of a neighboring organ after radiotherapy was nodular growth of the tumor into a neighboring structure.
  
  
  CONCLUSIONS
  The morphological assessment of pelvic MRI after preoperative radiotherapy does not provide any significant new information about tumor extent in patients with locally advanced rectal cancer.
authors.affiliation: Department of Radiology, Uppsala University Hospital, Uppsala, Sweden. mictor@ki.se
authors.forename: M R
authors.initials: MR
authors.lastname: Torkzad
authors.forename: C
authors.initials: C
authors.lastname: Suzuki
authors.forename: S
authors.initials: S
authors.lastname: Tanaka
authors.forename: G
authors.initials: G
authors.lastname: Palmer
authors.forename: T
authors.initials: T
authors.lastname: Holm
authors.forename: L
authors.initials: L
authors.lastname: Blomqvist
mesh_terms: D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D015588:Observer Variation; D010386:Pelvic Neoplasms / Q000175:diagnosis* / Q000556:secondary; D010388:Pelvis / Q000473:pathology; D011237:Predictive Value of Tests; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy* / Q000601:surgery; D012007:Rectum / Q000473:pathology / Q000528:radiation effects / Q000601:surgery; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index