title: Apparent diffusion coefficient as a non-invasive predictor of treatment response and recurrence in locally advanced rectal cancer.
abstract: OBJECTIVE
  To evaluate the role of pretreatment apparent diffusion coefficient (ADC) as a predictor of treatment response and local recurrence in patients with locally advanced rectal cancer who underwent neoadjuvant therapy.
  
  
  METHODS
  Forty-nine patients who underwent preoperative diffusion-weighted magnetic resonance imaging (MRI) followed by neoadjuvant chemoradiation and surgery were enrolled in the study. The mean tumour ADC was measured independently from multiple, non-overlapping regions of interest (ROIs) to cover the entire tumour area on a single section by two radiologists and patients were followed postoperatively for a median of 16.4 months. Diagnostic accuracy of ADC for predicting treatment response and recurrence was evaluated using the area under the receiver-operating characteristic (ROC) curve, sensitivity, specificity, and predictive values. Univariate and multivariate analyses including clinical tumour (cT) staging, carcinoembryonic antigen (CEA) level, lymph-node involvement, tumour grade, surgical margin, vascular involvement, and ADC were performed with respect to recurrence. Interobserver agreement of ADC values was assessed.
  
  
  RESULTS
  Twenty patients showed response to neoadjuvant therapy and recurrence was noted in 17 patients. Low pretreatment ADC, MRI findings of cT4 staging, and node involvement were significantly related to poor treatment response. Sensitivity and specificity of ADC = 0.833 × 10(-3) mm(2)/s for prediction of treatment response was 75 and 48% for reader 1 and 65 and 52% for reader 2, respectively. Univariate and multivariate analyses identified pretreatment tumour ADC as the only predictive factor for recurrence. Sensitivity and specificity of ADC = 0.833 × 10(-3) mm(2)/s for prediction of recurrence was 86 and 77% for reader 1 and 80 and 69% for reader 2, respectively. Interobserver agreement for measuring ADC was good with a kappa value of 0.70.
  
  
  CONCLUSIONS
  Pretreatment rectal tumour ADC values may be an early biomarker for predicting treatment response and local recurrence in patients who underwent neoadjuvant chemoradiation.
authors.affiliation: Division of Abdominal Imaging and Interventional Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA. aelmi@partners.org
authors.forename: A
authors.initials: A
authors.lastname: Elmi
authors.forename: S S
authors.initials: SS
authors.lastname: Hedgire
authors.forename: D
authors.initials: D
authors.lastname: Covarrubias
authors.forename: S M
authors.initials: SM
authors.lastname: Abtahi
authors.forename: P F
authors.initials: PF
authors.lastname: Hahn
authors.forename: M
authors.initials: M
authors.lastname: Harisinghani
mesh_terms: D059248:Chemoradiotherapy; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009364:Neoplasm Recurrence, Local; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D012372:ROC Curve; D012004:Rectal Neoplasms / Q000473:pathology* / Q000628:therapy*; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA