title: MRI after chemoradiotherapy of rectal cancer: a useful tool to select patients for local excision.
abstract: OBJECTIVE
  If identification of good responders to neoadjuvant chemoradiotherapy in rectal cancer is possible, there might be opportunities for local excision in selected patients. The aim of this study was to determine whether postchemoradiation MRI in rectal cancer can accurately identify ypT0 to 2/ypN0, because both features are essential for identification of good responders.
  
  
  METHODS
  Seventy-nine patients (4 hospitals) underwent postchemoradiation MRI, 62 received a lymph node-specific contrast agent (ultrasmall superparamagnetic iron oxide). An expert and general radiologist prospectively predicted whether the tumor penetrated the mesorectal fat and whether nodes were sterilized after chemoradiation. Histology was the reference standard. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated.
  
  
  RESULTS
  For prediction of whether a tumor penetrated the bowel wall, there was an negative predictive value of 0.90 and 0.76 for the expert and general radiologist, respectively. The negative predictive value for prediction of nodal status was 0.95 and 0.85 for expert and general radiologist, respectively.
  
  
  CONCLUSIONS
  This prospective multicenter study demonstrates that MRI with a lymph node-specific contrast agent interpreted by an expert radiologist can select ypT0 to 2/ypN0 rectal cancer with low risk of undetected nodal metastases or invasion through the bowel wall. These patients could thus have been selected for local excision. However, future studies will have to prove equal outcome of such a modified surgical approach compared with current practice.
authors.affiliation: Department of Surgery, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Sanne M E
authors.initials: SM
authors.lastname: Engelen
authors.forename: Regina G H
authors.initials: RG
authors.lastname: Beets-Tan
authors.forename: Max J
authors.initials: MJ
authors.lastname: Lahaye
authors.forename: Guido
authors.initials: G
authors.lastname: Lammering
authors.forename: Rob L H
authors.initials: RL
authors.lastname: Jansen
authors.forename: Ronald M
authors.initials: RM
authors.lastname: van Dam
authors.forename: Joop
authors.initials: J
authors.lastname: Konsten
authors.forename: Jeroen W A
authors.initials: JW
authors.lastname: Leijtens
authors.forename: Cornelis J H
authors.initials: CJ
authors.lastname: van de Velde
authors.forename: Geerard L
authors.initials: GL
authors.lastname: Beets
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D003082:Colectomy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D018579:Patient Selection; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D018714:Radiotherapy, Adjuvant; D012004:Rectal Neoplasms / Q000473:pathology* / Q000628:therapy
chemical_list: D000970:Antineoplastic Agents