title: Magnetic resonance-guided histopathology for improved accuracy of tumor response evaluation of neoadjuvant treatment in organ-infiltrating rectal cancer.
abstract: OBJECTIVE
  The novel procedure of magnetic resonance-(MR) guided histopathology was applied to determine the false-negative rate of conventional histopathologic tumor response evaluation of neoadjuvant radiation/chemoradiation therapy (RT/CRT) in organ-infiltrating rectal cancer.
  
  
  METHODS
  Ninety-two consecutive patients that had received RT/CRT and proceeded to extended total mesorectal excision for organ-infiltrating rectal cancer were identified from the institutional database. For each patient, the study radiologist and pathologist separately interpreted preoperative MR images and histologic preparations from the surgical specimen, to determine whether tumor down-staging had resulted. In cases of discrepancy (52 patients), histologic sections were jointly reassessed for residual tumor in areas outside the mesorectal fascial compartment, using MR images as guidance for where to inspect.
  
  
  RESULTS
  Following RT/CRT, 67.5% of cases were found to remain ypT4, even though half of the study population had complete (ypT0; 7.6%) or near-complete (sparsely remaining tumor; 43.5%) histomorphologic tumor regression. After MR-guided histologic reassessment of surgical specimens, the false-negative rate of conventional histopathology for detection of ypT4 was determined to be 41.1%. Five-year estimate for locally recurrent disease was 12.7%.
  
  
  CONCLUSIONS
  This response data to neoadjuvant RT/CRT in organ-infiltrating rectal cancer indicate that tumor down-staging is over-estimated by conventional evaluation.
authors.affiliation: Department of Radiology and Nuclear Medicine, The Norwegian Radium Hospital, Oslo, Norway.
authors.forename: Knut Håkon
authors.initials: KH
authors.lastname: Hole
authors.forename: Stein Gunnar
authors.initials: SG
authors.lastname: Larsen
authors.forename: Krystyna Kotanska
authors.initials: KK
authors.lastname: Grøholt
authors.forename: Karl-Erik
authors.initials: KE
authors.lastname: Giercksky
authors.forename: Anne Hansen
authors.initials: AH
authors.lastname: Ree
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059248:Chemoradiotherapy; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D012004:Rectal Neoplasms / Q000473:pathology / Q000628:therapy*; D012189:Retrospective Studies