title: Multiparametric MRI of rectal cancer in the assessment of response to therapy: a systematic review.
abstract: BACKGROUND
  Conventional MRI is limited in the assessment of nodal status and T status after neoadjuvant chemoradiotherapy. Multiparametric MRI strives to overcome these issues by directly measuring the local microcirculation and cellular environment, thus possibly allowing for a more reliable evaluation of response to therapy.
  
  
  OBJECTIVE
  We assessed the available literature for the value of multiparametric MRI sequences (diffusion-weighted and dynamic contrast-enhanced imaging) in determining the response to neoadjuvant chemoradiotherapy in patients with rectal cancer.
  
  
  METHODS
  We conducted a systematic literature research in the PubMed database.
  
  
  METHODS
  English-language publications of the years 2000-2013 that applied multiparametric MRI in the neoadjuvant setting were included in this study.
  
  
  METHODS
  Patients received neoadjuvant chemoradiotherapy and MRI examinations for staging and assessment of response.
  
  
  METHODS
  Accuracy, specificity, and sensitivity of MRI in prediction/assessment of response to therapy were the included measures.
  
  
  RESULTS
  Forty-three studies were included in this review; 30 of them included diffusion-weighted imaging sequences, and 13 included dynamic contrast-enhanced MRI. Conventional MRI is limited in the accuracy of both T and N stages and response assessment. Diffusion-weighted imaging and dynamic contrast-enhanced MRIs showed additional value in both the prediction and detection of (complete) response to therapy compared with conventional sequences alone, as well as in correct N staging along with new experimental contrast agents.
  
  
  CONCLUSIONS
  The lack of standardization represents an important technical limitation. Most studies are conducted in an experimental setting; therefore, larger multicenter prospective studies are needed to verify the present findings.
  
  
  CONCLUSIONS
  Advanced, functional MRI techniques allow for the quantification of tumor biological processes, such as microcirculation, vascular permeability, and tissue cellularity. This new technology has begun to show potential advantages over standard morphologic imaging in the restaging of rectal cancer, allowing for more accurate prognostication of response and potentially introducing an era allowing earlier treatment alteration and more accurate noninvasive surveillance, which could improve patient outcomes.
authors.affiliation: 1Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, New York 2Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, New York.
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Hötker
authors.forename: Julio
authors.initials: J
authors.lastname: Garcia-Aguilar
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Gollub
mesh_terms: D059186:Chemoradiotherapy, Adjuvant; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging; D006801:Humans; D020360:Neoadjuvant Therapy; D012004:Rectal Neoplasms / Q000628:therapy*; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media