title: Locally advanced rectal carcinoma treated with preoperative chemotherapy and radiation therapy: preliminary analysis of diffusion-weighted MR imaging for early detection of tumor histopathologic downstaging.
abstract: OBJECTIVE
  To determine whether changes in apparent diffusion coefficients (ADCs) of rectal carcinoma obtained 1 week after the beginning of chemotherapy and radiation therapy (CRT) correlate with tumor histopathologic downstaging after preoperative CRT.
  
  
  METHODS
  This prospective study was approved by an institutional review board; informed consent was obtained from all patients. Thirty-seven patients (mean age, 54.7 years; 13 women, 24 men) with primary rectal carcinoma who were undergoing preoperative CRT were recruited for the study. Diffusion-weighted (DW) magnetic resonance (MR) imaging was performed with a 1.5-T MR imager in all patients before therapy, at the end of the 1st and 2nd week of therapy, and before surgery. Tumor ADCs were calculated. Linear mixed-effects modeling was applied to analyze change in ADCs and volumes following treatment.
  
  
  RESULTS
  Patients were assigned to the tumor downstaged group (n = 17) or the tumor nondownstaged group (n = 20) on the basis of histopathologic examination results following surgery. Before CRT, the mean tumor ADC in the downstaged group was lower than that in the nondownstaged group (1.07 x 10(-3) mm(2)/sec +/- 0.13 [standard deviation] vs 1.19 x 10(-3) mm(2)/sec +/- 0.15, F = 6.91, P = .013). At the end of the 1st week of CRT, the mean tumor ADC increased significantly from 1.07 x 10(-3) mm(2)/sec +/- 0.13 to 1.32 x 10(-3) mm(2)/sec +/- 0.16 (F = 37.63, P <.001) in the downstaged group, but there was no significant ADC increase in the nondownstaged group (F = 1.18, P = .291). The mean percentage of tumor ADC change in the downstaged group was significantly higher than that in the nondownstaged group at each time point (F = 18.39, P < .001).
  
  
  CONCLUSIONS
  Early increase of mean tumor ADC and low pretherapy mean ADC in rectal carcinoma correlate with good response to CRT. DW MR imaging is a promising noninvasive technique for helping predict and monitor early therapeutic response in patients with rectal carcinoma who are undergoing CRT.
authors.affiliation: Key Laboratory of Carcinogenesis and Translational Research, Department of Radiology, Peking University School of Oncology, Beijing Cancer Hospital and Institute, Beijing, China.
authors.forename: Ying-Shi
authors.initials: YS
authors.lastname: Sun
authors.forename: Xiao-Peng
authors.initials: XP
authors.lastname: Zhang
authors.forename: Lei
authors.initials: L
authors.lastname: Tang
authors.forename: Jia-Fu
authors.initials: JF
authors.lastname: Ji
authors.forename: Jin
authors.initials: J
authors.lastname: Gu
authors.forename: Yong
authors.initials: Y
authors.lastname: Cai
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Zhang
mesh_terms: D000328:Adult; D000368:Aged; D003131:Combined Modality Therapy; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012004:Rectal Neoplasms / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy / Q000601:surgery; D016896:Treatment Outcome