title: Accuracy of pre-treatment locoregional rectal cancer staging in a national improvement project.
abstract: BACKGROUND
  The aim of this study was to assess the accuracy, particularly the predictive value, of locoregional clinical rectal cancer staging (cTN) and its variability in a national improvement project.
  
  
  METHODS
  cTN stages and the distance between tumour and mesorectal fascia (MRF) were compared with histopathological findings in 1168 patients who underwent radical resection without neoadjuvant treatment. Data were registered prospectively from 2006 to 2014.
  
  
  RESULTS
  Agreement between clinical and histopathological TN stages was 50%, independent of tumour location. Inter-hospital variability was within 99% prediction limits. Magnetic resonance imaging (MRI) was increasingly applied, but staging accuracy did not improve. Stage II-III was correctly predicted in 69% and pStage I was over-staged in 35%. The positive predictive value of endorectal ultrasonography (ERUS) for T1 lesions was 57%. MRI-based distances to MRF correlated poorly with the circumferential resection margin (r = 0.26). A negative resection margin was achieved in 91% when the distance to the MRF was >1 mm.
  
  
  CONCLUSIONS
  The accuracy of rectal cancer staging in general practice should be improved to avoid under- or overtreatment. Training and expert review of pre-treatment MR imaging could be helpful. A second ERUS is justified when transanal local resection for early lesions is planned.
authors.affiliation: a Department of Radiology , University Hospital , Antwerp , Belgium.
authors.forename: Bart
authors.initials: B
authors.lastname: Op de Beeck
authors.affiliation: b Department of Radiology , University Hospital , Gent , Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Smeets
authors.affiliation: c Department of Abdominal Surgery , University Hospital Gasthuisberg , Leuven , Belgium.
authors.forename: Freddy
authors.initials: F
authors.lastname: Penninckx
authors.affiliation: d Department of Gastrointestinal Surgery , University Hospital , Gent , Belgium.
authors.forename: Piet
authors.initials: P
authors.lastname: Pattyn
authors.affiliation: e Belgian Cancer Registry , Brussels , Belgium.
authors.forename: Geert
authors.initials: G
authors.lastname: Silversmit
authors.affiliation: e Belgian Cancer Registry , Brussels , Belgium.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Van Eycken
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000401:mortality / Q000473:pathology* / Q000628:therapy*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001530:Belgium; D016009:Chi-Square Distribution; D015331:Cohort Studies; D003082:Colectomy / Q000379:methods; D016001:Confidence Intervals; D016208:Databases, Factual; D018572:Disease-Free Survival; D019160:Endosonography / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy / Q000379:methods*; D009361:Neoplasm Invasiveness / Q000473:pathology; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D011379:Prognosis; D058996:Quality Improvement; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging / Q000401:mortality / Q000473:pathology* / Q000628:therapy*; D012189:Retrospective Studies; D018570:Risk Assessment; D016019:Survival Analysis; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome
keywords: Rectal cancer; cancer staging; computed tomography; endorectal ultrasonography; magnetic resonance imaging