title: Profiling of rectal cancers MRI in pathological complete remission states after neoadjuvant concurrent chemoradiation therapy.
abstract: OBJECTIVE
  To fully characterise the magnetic resonance imaging (MRI) traits of rectal cancers in a large sample of patients, each experiencing pathological complete remission (pCR) after neoadjuvant concurrent chemoradiation therapy (CCRT).
  
  
  METHODS
  A total of 120 patients (77 male, 43 female; median age, 59.5 years; range, 32-81 years) with rectal cancers in CCRT-induced pCR states who underwent pre- and post-CCRT MRI and eventual surgery between July, 2005 and September, 2014 were retrospectively reviewed. In most (n=100), diffusion-weighted imaging was also performed. Tumour volume, tumour regression grade (TRG), T-stage, mesorectal fascia (MRF) status, and T2 signal intensity (T2-SI) were analysed. Paired t-test and McNemar's test were applied for statistical comparisons.
  
  
  RESULTS
  Tumour volume declined sharply after CCRT (pre-CCRT, 21.5 ± 22.4 cm(3); post-CCRT, 6.6 ± 8.4 cm(3); p<0.001). TRG distribution was as follows: G1 (clinical CR), 3; G2, 38; G3, 78; G4, 1; and G5 (marked progression), 0. Downstaging of T-stage (34%,16/47) and MRF status (19.7%,13/66) did occur; but on post-CCRT MRI, 25.8% (31/120) remained at T3 ≥ 5 mm or T4 stage, and 44.2% (53/120) were MRF-positive. A majority (88.3%, 106/120) of patients displayed intermediate T2-SI prior to CCRT. Most converted to dark T2-SI after CCRT, with 12.5% (15/120) unchanged. On post-CCRT MRI, 11% (11/100) of patients showed diffusion restriction.
  
  
  CONCLUSIONS
  MRI findings in CCRT-induced pCR-status rectal cancers were highly variable. Tumour volume and T2-SI mostly decreased; however, such lesions occasionally presented with unexpected atypical features, such as large residual volume and/or intermediate T2-SI.
authors.affiliation: Department of Radiology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea; Research Institute of Radiological Science, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea.
authors.forename: H
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Pathology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea.
authors.forename: H M
authors.initials: HM
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea.
authors.forename: W S
authors.initials: WS
authors.lastname: Koom
authors.affiliation: Department of Surgery, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea.
authors.forename: N K
authors.initials: NK
authors.lastname: Kim
authors.affiliation: Department of Radiology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea; Research Institute of Radiological Science, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea.
authors.forename: M-J
authors.initials: MJ
authors.lastname: Kim
authors.affiliation: Department of Pathology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea.
authors.forename: H
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Surgery, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea.
authors.forename: H
authors.initials: H
authors.lastname: Hur
authors.affiliation: Department of Radiology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea; Research Institute of Radiological Science, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea. Electronic address: jslim1@yuhs.ac.
authors.forename: J S
authors.initials: JS
authors.lastname: Lim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059248:Chemoradiotherapy; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D060787:Neoplasm Grading; D009367:Neoplasm Staging; D012004:Rectal Neoplasms / Q000473:pathology* / Q000628:therapy*; D012074:Remission Induction; D016896:Treatment Outcome; D047368:Tumor Burden