title: Prediction of tumor stage and lymph node involvement with dynamic contrast-enhanced MRI after chemoradiotherapy for locally advanced rectal cancer.
abstract: OBJECTIVE
  The usefulness of restaging by magnetic resonance imaging (MRI) after chemoradiotherapy (CTx/RTx) in patients with locally advanced rectal cancer has not yet been established, mostly due to the difficult differentiation between viable tumor and fibrosis. MRI with dynamic contrast-enhanced (DCE) sequences may be of additional value in distinguishing malignant from nonmalignant tissue. The aim of this study was to assess the accuracy of tumor, nodal staging, and circumferential resection margin (CRM) involvement by MRI with DCE sequences after CTx/RTx.
  
  
  METHODS
  The accuracies were assessed by MRI on T2-weighted magnetic resonance (MR) images with DCE sequences in patients with locally advanced rectal cancer after a long course of CTx/RTx. MR images were assessed by two independent radiologists.
  
  
  RESULTS
  For tumor staging and CRM involvement, MRI with DCE sequences had an accuracy of 45 and 60 %, respectively. The accuracy for nodal staging was 93 %. On MRI, malignant lymph nodes had a median diameter of 8 mm (range, 4-18) and benign lymph nodes a median diameter of 4 mm (range, 3-11). A significant indicator for benign nodes was hypointensity on T2-weighted images (p < 0.001) and early complete arterial phase enhancement on DCE-weighted images (p < 0.001). A significant indicator for malignant nodes was heterogeneity on T2-weighted images (χ (2), p < 0.000) and early incomplete arterial phase enhancement on DCE (p < 0.001).
  
  
  CONCLUSIONS
  MRI with DCE is a useful tool for nodal staging after CTx/RTx. The addition of DCE sequences did not improve the accuracy of determining the tumor stage, CRM involvement, and in detecting complete response.
authors.affiliation: Department of Surgical Oncology, Erasmus MC-Daniël den Hoed Cancer Center, PO Box 5201, 3008 Rotterdam, the Netherlands.
authors.forename: Wijnand J
authors.initials: WJ
authors.lastname: Alberda
authors.forename: Helene P N
authors.initials: HP
authors.lastname: Dassen
authors.forename: Roy S
authors.initials: RS
authors.lastname: Dwarkasing
authors.forename: François E J A
authors.initials: FE
authors.lastname: Willemssen
authors.forename: Anne E M
authors.initials: AE
authors.lastname: van der Pool
authors.forename: Johannes H W
authors.initials: JH
authors.lastname: de Wilt
authors.forename: Jacobus W A
authors.initials: JW
authors.lastname: Burger
authors.forename: Cornelis
authors.initials: C
authors.lastname: Verhoef
mesh_terms: D000328:Adult; D000368:Aged; D059248:Chemoradiotherapy; D003287:Contrast Media; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis / Q000175:diagnosis; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011859:Radiography; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery / Q000628:therapy*
chemical_list: D003287:Contrast Media