title: Diffusion-weighted MRI for selection of complete responders after chemoradiation for locally advanced rectal cancer: a multicenter study.
abstract: OBJECTIVE
  In 10-24% of patients with rectal cancer who are treated with neoadjuvant chemoradiation, no residual tumor is found after surgery (ypT0). When accurately selected, these complete responders might be considered for less invasive treatments instead of standard surgery. So far, no imaging method has proven reliable. This study was designed to assess the accuracy of diffusion-weighted MRI (DWI) in addition to standard rectal MRI for selection of complete responders after chemoradiation.
  
  
  METHODS
  A total of 120 patients with locally advanced rectal cancer from three university hospitals underwent chemoradiation followed by a restaging MRI (1.5T), consisting of standard T2W-MRI and DWI (b0-1000). Three independent readers first scored the standard MRI only for the likelihood of a complete response using a 5-point confidence score, after which the DWI images were added and the scoring was repeated. Histology (ypT0 vs. ypT1-4) was the standard reference. Diagnostic performance for selection of complete responders and interobserver agreement were compared for the two readings.
  
  
  RESULTS
  Twenty-five of 120 patients had a complete response (ypT0). Areas under the ROC-curve for the three readers improved from 0.76, 0.68, and 0.58, using only standard MRI, to 0.8, 0.8, and 0.78 after addition of DWI (P = 0.39, 0.02, and 0.002). Sensitivity for selection of complete responders ranged from 0-40% on standard MRI versus 52-64% after addition of DWI. Specificity was equally high (89-98%) for both reading sessions. Interobserver agreement improved from κ 0.2-0.32 on standard MRI to 0.51-0.55 after addition of DWI.
  
  
  CONCLUSIONS
  Addition of DWI to standard rectal MRI improves the selection of complete responders after chemoradiation.
authors.affiliation: Department of Radiology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Doenja M J
authors.initials: DM
authors.lastname: Lambregts
authors.forename: Vincent
authors.initials: V
authors.lastname: Vandecaveye
authors.forename: Brunella
authors.initials: B
authors.lastname: Barbaro
authors.forename: Frans C H
authors.initials: FC
authors.lastname: Bakers
authors.forename: Maarten
authors.initials: M
authors.lastname: Lambrecht
authors.forename: Monique
authors.initials: M
authors.lastname: Maas
authors.forename: Karin
authors.initials: K
authors.lastname: Haustermans
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Valentini
authors.forename: Geerard L
authors.initials: GL
authors.lastname: Beets
authors.forename: Regina G H
authors.initials: RG
authors.lastname: Beets-Tan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D000069287:Capecitabine; D059248:Chemoradiotherapy; D017024:Chemotherapy, Adjuvant; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage / Q000031:analogs & derivatives; D005500:Follow-Up Studies; D005720:Gamma Rays; D006801:Humans; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis / Q000628:therapy; D018365:Neoplasm, Residual / Q000175:diagnosis / Q000628:therapy; D009944:Organoplatinum Compounds / Q000008:administration & dosage; D000077150:Oxaliplatin; D018714:Radiotherapy, Adjuvant; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000628:therapy*; D012189:Retrospective Studies; D015996:Survival Rate; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D009944:Organoplatinum Compounds; D000077150:Oxaliplatin; D003841:Deoxycytidine; D000069287:Capecitabine; D005472:Fluorouracil