title: Extended total mesorectal excision in locally advanced rectal cancer (T4a) and the clinical role of MRI-evaluated neo-adjuvant downstaging.
abstract: OBJECTIVE
  To compare the clinical ability of MRl taken before and after neo-adjuvant treatment in locally advanced rectal cancer (LARC) to predict the necessary extension of TME (ETME) and the possibility to achieve a R0 resection.
  
  
  METHODS
  Prospective registration of 92 MRI evaluated T4a cancers undergoing elective surgery between 2002 and 2007 in a tertiary referral centre for multimodal treatment of rectal cancer.
  
  
  RESULTS
  MRI identified patients in need of neo-adjuvant treatment and predicted T-downstaging in 10% and N-downstaging in 59%. Seventy-nine percent R0 resections, 18% R1 and 3% R2 were obtained after ETME in 95% of the patients and TME in the rest. Higher tumour regression grade (TRG) was achieved in higher ypT-stage (P < 0.01). Preoperative chemo radiotherapy resulted in that more patients obtained TRG1-3 compared to those receiving radiotherapy (79% vs. 57%, P = 0.02). The pelvic wall was the area of failure in 70% of the R1 resections. Tumour cells outside the mesorectal fascia scattered within fibrosis was found in 18 TRG2-3 among 33 ypT4 tumours (55%).
  
  
  CONCLUSIONS
  MRl cannot discriminate tumour within fibrosis. Therefore, if a R0 resection is the goal, we advocate optimal surgery in accordance with the pre-treatment MRI. Post treatment MRI is a poor predictor of final histology and should not be relied upon to guide the extent of surgical resection. The study has initiated a new approach to histopathological classification of the removed specimen where we introduce a MRI assisted technique for investigating the areas at risk outside the mesorectal fascia in the specimen.
authors.affiliation: Department of Surgical Oncology, the Norwegian Radium Hospital, Rikshospitalet University Hospital, Oslo, Norway. stein.larsen@radiumhospitalet.no
authors.forename: S G
authors.initials: SG
authors.lastname: Larsen
authors.forename: J N
authors.initials: JN
authors.lastname: Wiig
authors.forename: H L
authors.initials: HL
authors.lastname: Emblemsvaag
authors.forename: K K
authors.initials: KK
authors.lastname: Grøholt
authors.forename: K H
authors.initials: KH
authors.lastname: Hole
authors.forename: A
authors.initials: A
authors.lastname: Bentsen
authors.forename: S
authors.initials: S
authors.lastname: Dueland
authors.forename: T
authors.initials: T
authors.lastname: Vetrhus
authors.forename: K-E
authors.initials: KE
authors.lastname: Giercksky
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology* / Q000601:surgery*; D017024:Chemotherapy, Adjuvant; D005260:Female; D005355:Fibrosis / Q000150:complications / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D020360:Neoadjuvant Therapy; D009367:Neoplasm Staging / Q000379:methods; D011446:Prospective Studies; D018714:Radiotherapy, Adjuvant; D012004:Rectal Neoplasms / Q000473:pathology* / Q000601:surgery*