title: Differentiating locally recurrent rectal cancer from scar tissue: Value of diffusion-weighted MRI.
abstract: OBJECTIVE
  To determine a cut-off apparent diffusion coefficient (ADC) value distinguishing local recurrence from scar tissue in patients with rectal cancer treated with complete surgical tumour removal.
  
  
  METHODS
  72 patients were retrospectively included. Patients underwent 1.5T MRI including multiplanar T2-weighted turbo-spin-echo sequences (TSE) and axial single-shot epi-diffusion-weighted sequences (EPSE). Two independent observers measured mean tumour and scar tissue ADCs by manually drawing regions of interest (ROIs). The t-test and ROC analysis were used for comparison and determining an optimal discrimination threshold. As reference standard histopathological results were used in 23 patients (32%) and clinical follow-up in 49 patients (68%).
  
  
  RESULTS
  Recurrent rectal cancer was found in 30 patients (4 female, 26 male, median age 63.13 years) and treatment related changes such as scar tissue in 42 patients (11 female, 31 male, median age 63.67 years). The mean ADC value of tumour recurrence was 1.02×10(-3)mm(2)/s (0.63-1.44×10(-3)mm(2)/s) and of scar tissue 1.77×10(-3)mm(2)/s (1.11-2.41×10(-3)mm(2)/s) showing a statistically significant difference (p<0.001). The cut-off ADC value was 1.34×10(-3)mm(2)/s with a sensitivity, specificity, and accuracy of 93%, 91%, and 92% respectively.
  
  
  CONCLUSIONS
  Diffusion weighted MRI allows for the differentiation of tumour recurrence from scar tissue after surgical resection of rectal cancer.
authors.affiliation: Department of Radiology, University Medical Center Freiburg, Hugstetter Straße 55, D-79106 Freiburg, Germany. Electronic address: sergio.grosu@uniklinik-freiburg.de.
authors.forename: Sergio
authors.initials: S
authors.lastname: Grosu
authors.affiliation: Department of Diagnostic and Interventional Radiology, Sankt Georg Hospital Leipzig, Delitzscher Str. 141, D-04129 Leipzig, Germany.
authors.forename: Arnd-Oliver
authors.initials: AO
authors.lastname: Schäfer
authors.affiliation: Department of Radiology and Nuclear Medicine, University Hospital Basel, Petersgraben 4, CH-4031 Basel, Switzerland.
authors.forename: Tobias
authors.initials: T
authors.lastname: Baumann
authors.affiliation: Department of General and Visceral Surgery, University Medical Center Freiburg, Hugstetter Straße 55, D-79106 Freiburg, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Manegold
authors.affiliation: Department of Radiology, University Medical Center Freiburg, Hugstetter Straße 55, D-79106 Freiburg, Germany.
authors.forename: Mathias
authors.initials: M
authors.lastname: Langer
authors.affiliation: Department of Radiology, Ortenau Klinikum Offenburg-Gengenbach, Ebertplatz 12, D-77654 Offenburg, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Gerstmair
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002921:Cicatrix / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging* / Q000473:pathology; D012372:ROC Curve; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
keywords: Diffusion weighted MRI; Magnetic resonance imaging; Rectal cancer; Recurrence; Scar