title: Multicenter Evaluation of Rectal cancer ReImaging pOst Neoadjuvant (MERRION) Therapy.
abstract: OBJECTIVE
  The aim of this study was to evaluate the utility of reimaging rectal cancer post-CRT (chemoradiotherapy) with magnetic resonance (MR) imaging of the pelvis for local staging and computed tomography of thorax, abdomen, and pelvis (CT TAP) to identify distant metastases.
  
  
  BACKGROUND
  The success of neoadjuvant CRT for locally advanced rectal cancer has changed an already complex management algorithm. There is no consensus whether patients should be restaged before surgery.
  
  
  METHODS
  Data from 5 institutions with prospectively maintained databases including patients who received neoadjuvant CRT for locally advanced rectal cancer were acquired. Only patients who had been staged pre- and post-CRT with MR imaging and CT TAP were included. MR findings were correlated with histopathological stage using weighted κ (kappa) statistics to test agreement, where a κ value of less than 0.5 was deemed unacceptable.
  
  
  RESULTS
  A total of 285 patients fulfilled the criteria for the study; 84% had American Joint Committee for Cancer stage 3 disease pre-CRT, and the remainder had stage 2 disease. Fourteen patients did not proceed to surgery post-CRT-2 were observed as "complete responders," and the remainder either had unresectable disease or were unfit for surgery. MR imaging could not predict T stage (κ = 0.212) or nodal involvement (κ = 0.336). Most pertinently, MR imaging was unable to detect a complete pathological response (κ = 0.021), nor could it discriminate T4 disease (κ = 0.445). CT TAP restaging altered management in 6.7% of patients, who had metastatic disease.
  
  
  CONCLUSIONS
  MR reimaging using standard protocols is of limited value in determining surgical approaches; a better modality of local restaging is required.
authors.affiliation: *Centre for Colorectal Disease, St Vincent's University Hospital, Elm Park, Dublin, Ireland †Beaumont Hospital, Dublin, Ireland ‡University of Minnesota Medical Center, Minnesota, Minneapolis, MN.
authors.forename: Ann M
authors.initials: AM
authors.lastname: Hanly
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Ryan
authors.forename: Ailín C
authors.initials: AC
authors.lastname: Rogers
authors.forename: Deborah A
authors.initials: DA
authors.lastname: McNamara
authors.forename: Robert D
authors.initials: RD
authors.lastname: Madoff
authors.forename: Desmond C
authors.initials: DC
authors.lastname: Winter
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059186:Chemoradiotherapy, Adjuvant; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009367:Neoplasm Staging; D011300:Preoperative Care / Q000379:methods*; D012004:Rectal Neoplasms / Q000473:pathology* / Q000628:therapy; D012007:Rectum / Q000601:surgery; D012189:Retrospective Studies; D016896:Treatment Outcome