title: MR imaging of locally advanced low rectal cancer: Relationships between imaging findings and the pathological tumor regression grade.
abstract: BACKGROUND
  To evaluate the relationship between MR measurements and the pathological tumor regression grade (pTRG).
  
  
  METHODS
  Two radiologists independently reviewed the pre- and postchemoradiation therapy (CRT) rectal MR images of 73 consecutive patients with locally advanced low rectal cancer who underwent neoadjuvant CRT and subsequent surgery and measured tumor diameter, area, signal intensity (SI). The percentage reduction rate for each parameter was calculated. The absolute SI ratio reduction rate was defined as the absolute value of the SI ratio reduction rate. The Kruskal-Wallis test and multivariate analysis were performed to assess the correlation between each parameter and the pTRG. Receiver operating characteristic (ROC) curves were plotted for predicting favorable regression outcomes (pTRG 3-4).
  
  
  RESULTS
  In multivariate analysis, the absolute SI ratio reduction rate was a significant predictor of pTRG for both radiologists. Area under the ROC curve (Az) values were 0.77-0.709 for diameter reduction rate, 0.757-0.694 for area, 0.652-0.648 for the SI ratio, 0.736-0.837 for the absolute SI ratio.
  
  
  CONCLUSIONS
  The absolute SI ratio reduction rate was significantly associated with pTRG and predicted favorable responses to CRT. Measurement of the diameter reduction rate is convenient and reliable in predicting favorable responses.
authors.affiliation: Division of Radiology, Department of Pathophysiological and Therapeutic Science, Faculty of Medicine, Tottori University, Yonago, Japan.|Department of Abdominal Imaging, MUHC McGill University, Montreal, Canada.
authors.forename: Shinya
authors.initials: S
authors.lastname: Fujii
authors.affiliation: Department of Abdominal Imaging, MUHC McGill University, Montreal, Canada.|Department of Imaging, CHU Montpellier, St Eloi Hospital, Montpellier, France.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Nougaret
authors.affiliation: Department of Imaging, CHU Montpellier, St Eloi Hospital, Montpellier, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Escal
authors.affiliation: Department of Radiotherapy, ICM, Montpellier, France.
authors.forename: David
authors.initials: D
authors.lastname: Azria
authors.affiliation: Department of Oncology, CHU Montpellier, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Assenat
authors.affiliation: Department of Surgery, ICM, Montpellier, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Rouanet
authors.affiliation: Department of Abdominal Imaging, MUHC McGill University, Montreal, Canada.
authors.forename: Caroline
authors.initials: C
authors.lastname: Reinhold
authors.affiliation: Department of Imaging, CHU Montpellier, St Eloi Hospital, Montpellier, France.
authors.forename: Boris
authors.initials: B
authors.lastname: Guiu
mesh_terms: D000328:Adult; D000368:Aged; D059248:Chemoradiotherapy; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D009365:Neoplasm Regression, Spontaneous / Q000473:pathology*; D009367:Neoplasm Staging; D012004:Rectal Neoplasms / Q000473:pathology* / Q000628:therapy*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
keywords: MRI; chemoradiation therapy; rectal cancer; tumor regression grade