title: Best MRI predictors of complete response to neoadjuvant chemoradiation in locally advanced rectal cancer.
abstract: OBJECTIVE
  To identify the MRI parameters which best predict complete response (CR) to neoadjuvant chemoradiotherapy (CRT) in patients with locally advanced rectal cancer (LARC) and to assess their diagnostic performance.
  
  
  METHODS
  This was a prospective study of pre- and post-CRT MRI and diffusion-weighted imaging (DWI) of 64 patients with LARC who underwent neoadjuvant CRT and subsequent surgery. Histopathological tumour regression grade was the reference standard. Multivariate regression analysis was performed to identify the best MRI predictors of CR to neoadjuvant CRT, and their diagnostic performance was assessed.
  
  
  RESULTS
  The study cohort comprised 48 males and 16 females (n = 64), with mean age of 49.48 ± 14.3 years, range of 23-74 years. 11 patients had pathological complete response. The following factors predicted CR on univariate analysis: low initial (pre-CRT) tumour volume on T2 weighted high-resolution (HR) images and DWI, tumour volume-reduction rate (TVRR) of >95% on DWI and CR on post-CRT DWI (ydwiT0) as assessed by the radiologist. However, the best MRI predictors of CR on multivariate regression analysis were CR on post-CRT DWI (ydwiT0) as assessed by the radiologist and TVRR of >95% on DWI, and these parameters had an area under the curve (95% confidence interval) of 0.881 (0.74-1.0) and 0.843 (0.7-0.98), respectively. The sensitivity, specificity, positive-predictive value, negative-predictive value and accuracy of DWI in predicting CR was 81.8%, 94.3%, 75%, 96.1% and 76%; the sensitivity, specificity and accuracy of TVRR of >95% as a predictor of CR was 80%, 84.1% and 64.1%, respectively; however, this difference was not statistically significant. The interobserver agreement was substantial for ydwiT0.
  
  
  CONCLUSIONS
  Visual assessment of CR on post-CRT DWI and TVRR of >95% on DWI were the best predictors of CR after neoadjuvant CRT in patients with LARC, and the former being more practical can be used in daily practice.
  
  
  CONCLUSIONS
  In rectal cancer, ydwiT0 as assessed by the radiologist was the best and most practical imaging predictor of CR and scores over standard T2W HR images.
authors.affiliation: 1 Department of Radiology, Christian Medical College, Vellore, Tamil Nadu, India.
authors.forename: Kirthi
authors.initials: K
authors.lastname: Sathyakumar
authors.affiliation: 1 Department of Radiology, Christian Medical College, Vellore, Tamil Nadu, India.
authors.forename: Anuradha
authors.initials: A
authors.lastname: Chandramohan
authors.affiliation: 2 Department of Pathology, Christian Medical College, Vellore, Tamil Nadu, India.
authors.forename: Dipti
authors.initials: D
authors.lastname: Masih
authors.affiliation: 3 Department of General and Colorectal Surgery, Unit II, Christian Medical College, Vellore, Tamil Nadu, India.
authors.forename: Mark Ranjan
authors.initials: MR
authors.lastname: Jesudasan
authors.affiliation: 2 Department of Pathology, Christian Medical College, Vellore, Tamil Nadu, India.
authors.forename: Anna
authors.initials: A
authors.lastname: Pulimood
authors.affiliation: 1 Department of Radiology, Christian Medical College, Vellore, Tamil Nadu, India.
authors.forename: Anu
authors.initials: A
authors.lastname: Eapen
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology / Q000628:therapy*; D000328:Adult; D000368:Aged; D059186:Chemoradiotherapy, Adjuvant / Q000379:methods*; D054893:Cone-Beam Computed Tomography / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D012004:Rectal Neoplasms / Q000473:pathology / Q000628:therapy*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D055815:Young Adult
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