title: Locally advanced rectal cancer: MR imaging in prediction of response after preoperative chemotherapy and radiation therapy.
abstract: OBJECTIVE
  To prospectively differentiate, at magnetic resonance (MR) imaging, patients with locally advanced nonmucinous rectal cancer who will respond to long-course chemotherapy and radiation therapy (CRT) from those who will not respond, with histopathologic results as the reference standard.
  
  
  METHODS
  Institutional review board approval for this study was obtained, and all patients provided written informed consent. High-spatial-resolution T2-weighted MR images were acquired before and 6-8 weeks after CRT in 53 patients (33 men, 20 women; mean age, 63 years; age range, 42-79 years). Patients were categorized as responders to CRT (patients with T3 cancer that converted to T2 or a lower stage, patients with T4 cancer that converted to T3 or a lower stage) or as nonresponders (patients with stable or progressive disease). At the posttreatment MR imaging examination, a decrease in signal intensity was considered to represent a morphologic response with fibrosis. Before CRT and surgery, tumor volume was calculated at MR imaging by multiplying cross-sectional area by section thickness. Tumor length was measured at MR imaging and in the histopathologic specimen. Nodal downstaging was evaluated. The relationship between pathologic response, morphologic MR imaging response, and percentage volume reduction was evaluated with the Mann-Whitney-Wilcoxon two-sample test.
  
  
  RESULTS
  Morphologic response assessment with MR imaging achieved a positive predictive value (PPV) of 84.2% (32 of 38) and a negative predictive value (NPV) of 66.7% (10 of 15). Volume reduction extent (> or = 70%) was significantly different between patients in whom disease was downstaged and those in whom it was not downstaged (P = .000005) and showed additional diagnostic value, with an overall accuracy of 86.8% (46 of 53). Presurgical MR imaging and histopathologic tumor length did not show a significant difference. MR imaging accuracy for lymph node (N) stage was 86.8% (46 of 53) on the basis of morphologic criteria.
  
  
  CONCLUSIONS
  After CRT, morphologic and volumetric evaluation at MR imaging had a high PPV and a low NPV for response assessment. The detection of small clusters of residual tumor cells within fibrosis remains a problem.
  
  
  BACKGROUND
  http://radiology.rsnajnls.org/cgi/content/full/250/3/730/DC1.
authors.affiliation: Department of Bioimaging and Radiological Sciences, Catholic University, School of Medicine, Policlinico A. Gemelli, Largo Gemelli, 1, 00168 Rome, Italy. bbarbaro@rm.unicatt.it
authors.forename: Brunella
authors.initials: B
authors.lastname: Barbaro
authors.forename: Cecilia
authors.initials: C
authors.lastname: Fiorucci
authors.forename: Carmen
authors.initials: C
authors.lastname: Tebala
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Valentini
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Gambacorta
authors.forename: Fabio Maria
authors.initials: FM
authors.lastname: Vecchio
authors.forename: Gianluca
authors.initials: G
authors.lastname: Rizzo
authors.forename: Claudio
authors.initials: C
authors.lastname: Coco
authors.forename: Antonio
authors.initials: A
authors.lastname: Crucitti
authors.forename: Carlo
authors.initials: C
authors.lastname: Ratto
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Bonomo
mesh_terms: D000328:Adult; D000368:Aged; D017024:Chemotherapy, Adjuvant / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care / Q000379:methods*; D011379:Prognosis; D018714:Radiotherapy, Adjuvant / Q000379:methods*; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000628:therapy*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome