title: MRI-based treatment of rectal cancer: is prognostication of the recurrence risk solid enough to render radiation redundant?
abstract: BACKGROUND
  Most current guidelines recommend neoadjuvant short course radiotherapy (sRT) or radio-chemotherapy (nRCT) for rectal cancer stage II and III. After the introduction of total mesorectal excision (TME) and magnetic resonance imaging (MRI), this proceeding has been questioned and omission of neoadjuvant treatment according to preoperative MRI-criteria has been propagated. Aim of the present paper is to review the state of evidence regarding MRI-based treatment decision depending on the predicted width of the circumferential resection margin (CRM).
  
  
  METHODS
  A comprehensive survey of the literature was performed using the search terms "rectal cancer", "radiotherapy", "radio-chemotherapy", "MRI-based therapy", "circumferential resection margin". Data from lately published observational studies were compared to results from randomized trials and outcome analyses of the Norwegian national cancer registry.
  
  
  RESULTS
  Only one observational study using MRI-based treatment according to the anticipated CRM provided 5 year local recurrence data, however only for 65 patients. The second study did not yet evaluate recurrence rates. Two randomized trials comparing sRT to primary TME showed significantly worse outcome for non-irradiated patients. Data from the Norwegian rectal cancer registry demonstrate that TME alone is associated with higher LRR than achievable with preoperative RT.
  
  
  CONCLUSIONS
  Current evidence does not support the omission of neoadjuvant treatment for stage II-III rectal cancer on the basis of an MRI-predicted negative CRM. Randomized studies are warranted to clarify whether and for which subgroups TME alone is safe in terms of local recurrences.
authors.affiliation: Department of Radiation Oncology, Städtisches Klinikum Karlsruhe, Karlsruhe, Germany, sautterbihl@aol.com.
authors.forename: Marie-Luise
authors.initials: ML
authors.lastname: Sautter-Bihl
authors.forename: Werner
authors.initials: W
authors.lastname: Hohenberger
authors.forename: Rainer
authors.initials: R
authors.lastname: Fietkau
authors.forename: Claus
authors.initials: C
authors.lastname: Roedel
authors.forename: Heinz
authors.initials: H
authors.lastname: Schmidberger
authors.forename: Rolf
authors.initials: R
authors.lastname: Sauer
mesh_terms: D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D020360:Neoadjuvant Therapy / Q000009:adverse effects*; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis* / Q000209:etiology; D011379:Prognosis; D011878:Radiotherapy; D016032:Randomized Controlled Trials as Topic; D012004:Rectal Neoplasms / Q000150:complications / Q000473:pathology / Q000628:therapy*