title: Accuracy of MRI and 18F-FDG PET/CT for restaging after preoperative concurrent chemoradiotherapy for rectal cancer.
abstract: BACKGROUND
  Performing a restaging work-up with magnetic resonance imaging (MRI) and (18)F-fluorodeoxyglucose-positron emission tomography/computed tomography ((18)F-FDG PET/CT) can provide information about the effects that are related to preoperative concurrent chemoradiotherapy (CCRT). The purpose of the present study was to investigate the accuracy of MRI and (18)F-FDG PET/CT for restaging after preoperative CCRT for rectal cancer.
  
  
  METHODS
  Between April 2005 and February 2006, 30 patients with histologically proven rectal adenocarcinoma were included in this study. Pelvic MRI and (18)F-FDG PET/CT were performed to clinically restage the tumor after CCRT. The results of the pathologic staging were correlated with those of the MRI and (18)F-FDG PET/CT after CCRT. Two patients underwent transanal endoscopic microsurgery after CCRT, and they were excluded when the N category was evaluated.
  
  
  RESULTS
  The overall accuracy of MRI for the T category was 67% (kappa = 0.422, P = 0.003), whereas overstaging and understaging occurred in 30 and 3% of the patients, respectively. For the N category, accurate staging was noted in 75% (kappa = 0.410, P = 0.030) of all the patients, whereas 14% were overstaged and 11% were understaged. The overall accuracy rates for the T and N categories with performing (18)F-FDG PET/CT were 60% (kappa = 0.372, P = 0.004) and 71% (kappa = 0.097, P = 0.549), respectively. While MRI could not predict any patient who showed a pathologic complete response, (18)F-FDG PET/CT predicted three of the four patients who showed a pathologic complete response after preoperative CCRT. Furthermore, (18)F-FDG PET/CT identified distant metastases with an accuracy rate of 97%.
  
  
  CONCLUSIONS
  For restaging patients with rectal cancer after preoperative CCRT, MRI is a useful diagnostic modality to predict both the T and N categories. (18)F-FDG PET/CT is helpful in predicting a pathologic complete response and in finding metastasis after preoperative CCRT.
authors.affiliation: Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul 135-710, Korea.
authors.forename: Yong Beom
authors.initials: YB
authors.lastname: Cho
authors.forename: Ho-Kyung
authors.initials: HK
authors.lastname: Chun
authors.forename: Min Ju
authors.initials: MJ
authors.lastname: Kim
authors.forename: Joon Young
authors.initials: JY
authors.lastname: Choi
authors.forename: Chi-Min
authors.initials: CM
authors.lastname: Park
authors.forename: Byung-Tae
authors.initials: BT
authors.lastname: Kim
authors.forename: Soon Jin
authors.initials: SJ
authors.lastname: Lee
authors.forename: Seong Hyeon
authors.initials: SH
authors.lastname: Yun
authors.forename: Hee Cheol
authors.initials: HC
authors.lastname: Kim
authors.forename: Woo Yong
authors.initials: WY
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D003131:Combined Modality Therapy; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009367:Neoplasm Staging / Q000379:methods; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000628:therapy*; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18