title: Preoperative assessment of prognostic factors in rectal cancer using high-resolution magnetic resonance imaging.
abstract: BACKGROUND
  The aim was to determine the accuracy of preoperative magnetic resonance imaging (MRI) in the evaluation of pathological prognostic factors that influence local recurrence and survival in rectal cancer.
  
  
  METHODS
  Ninety-eight patients undergoing total mesorectal excision for biopsy-proven rectal cancer were assessed prospectively using high-resolution MRI for tumour (T) and nodal (N) staging using the tumour node metastasis classification, depth of extramural tumour spread, the presence or absence of extramural venous invasion, a threatened circumferential resection margin and serosal involvement at or above the peritoneal reflection. Preoperative magnetic resonance assessment of these prognostic factors was compared with histopathological findings in carefully matched whole-mount sections of the resection specimen.
  
  
  RESULTS
  There was 94 per cent weighted agreement (weighted kappa = 0.67) between MRI and pathology assessment of T stage. Agreement between MRI and histological assessment of nodal status was 85 per cent (kappa = 0.68). Although involvement of small veins by tumour was not discernible using MRI, large (calibre greater than 3 mm) extramural venous invasion was identified correctly in 15 of 18 patients (kappa = 0.64). MRI predicted circumferential resection margin involvement with 92 per cent agreement (kappa = 0.81). Seven of nine patients with peritoneal perforation by tumour (stage T4) were identified correctly using MRI.
  
  
  CONCLUSIONS
  High-resolution MRI of the rectum allows preoperative identification of important surgical and pathological prognostic risk factors. This may allow both better selection and assessment of patients undergoing preoperative therapy.
authors.affiliation: Cardiff and the Vale NHS Trust, University of Wales College of Medicine, Cardiff, UK. gina.brown@rmh.nthames.nhs.uk
authors.forename: G
authors.initials: G
authors.lastname: Brown
authors.forename: A G
authors.initials: AG
authors.lastname: Radcliffe
authors.forename: R G
authors.initials: RG
authors.lastname: Newcombe
authors.forename: N S
authors.initials: NS
authors.lastname: Dallimore
authors.forename: M W
authors.initials: MW
authors.lastname: Bourne
authors.forename: G T
authors.initials: GT
authors.lastname: Williams
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008207:Lymphatic Metastasis; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000592:standards*; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging / Q000379:methods; D010537:Peritoneum; D011300:Preoperative Care / Q000379:methods; D011379:Prognosis; D011446:Prospective Studies; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000473:pathology; D012307:Risk Factors; D012422:Rupture, Spontaneous