title: Locally advanced rectal cancer: post-chemoradiotherapy ADC histogram analysis for predicting a complete response.
abstract: BACKGROUND
  The value of diffusion-weighted imaging (DWI) for reliable differentiation between pathologic complete response (pCR) and residual tumor is still unclear. Recently, a few studies reported that histogram analysis can be helpful to monitor the therapeutic response in various cancer research.
  
  
  OBJECTIVE
  To investigate whether post-chemoradiotherapy (CRT) apparent diffusion coefficient (ADC) histogram analysis can be helpful to predict a pCR in locally advanced rectal cancer (LARC).
  
  
  METHODS
  Fifty patients who underwent preoperative CRT followed by surgery were enrolled in this retrospective study, non-pCR (n = 41) and pCR (n = 9), respectively. ADC histogram analysis encompassing the whole tumor was performed on two post-CRT ADC600 and ADC1000 (b factors 0, 600 vs. 0, 1000 s/mm(2)) maps. Mean, minimum, maximum, SD, mode, 10th, 25th, 50th, 75th, 90th percentile ADCs, skewness, and kurtosis were derived. Diagnostic performance for predicting pCR was evaluated and compared.
  
  
  RESULTS
  On both maps, 10th and 25th ADCs showed better diagnostic performance than that using mean ADC. Tenth percentile ADCs revealed the best diagnostic performance on both ADC600 (AZ 0.841, sensitivity 100%, specificity 70.7%) and ADC1000 (AZ 0.821, sensitivity 77.8%, specificity 87.8%) maps. In comparison between 10th percentile and mean ADC, the specificity was significantly improved on both ADC600 (70.7% vs. 53.7%; P = 0.031) and ADC1000 (87.8% vs. 73.2%; P = 0.039) maps.
  
  
  CONCLUSIONS
  Post-CRT ADC histogram analysis is helpful for predicting pCR in LARC, especially, in improving the specificity, compared with mean ADC.
authors.affiliation: Department of Radiology, Kyungpook National University Medical Center, School of Medicine, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Cho
authors.affiliation: Department of Radiology, Kyungpook National University Medical Center, School of Medicine, Kyungpook National University, Daegu, Republic of Korea gckim3378@gmail.com.
authors.forename: Gab Chul
authors.initials: GC
authors.lastname: Kim
authors.affiliation: Department of Radiology, Kyungpook National University Hospital, School of Medicine, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Yun-Jin
authors.initials: YJ
authors.lastname: Jang
authors.affiliation: Department of Radiology, Kyungpook National University Hospital, School of Medicine, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Hunkyu
authors.initials: H
authors.lastname: Ryeom
authors.affiliation: Department of Radiology, Kyungpook National University Medical Center, School of Medicine, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Hye Jung
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Radiology, Kyungpook National University Medical Center, School of Medicine, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Kyung-Min
authors.initials: KM
authors.lastname: Shin
authors.affiliation: Colorectal Cancer Center, Kyungpook National University Medical Center, School of Medicine, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Jun Seok
authors.initials: JS
authors.lastname: Park
authors.affiliation: Colorectal Cancer Center, Kyungpook National University Medical Center, School of Medicine, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Gyu-Seog
authors.initials: GS
authors.lastname: Choi
authors.affiliation: Department of Radiology, Dongsan Hospital, College of Medicine, Keimyung University, Daegu, Republic of Korea.
authors.forename: See Hyung
authors.initials: SH
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059248:Chemoradiotherapy; D003131:Combined Modality Therapy; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D013505:Digestive System Surgical Procedures; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D012004:Rectal Neoplasms / Q000473:pathology* / Q000628:therapy*; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: Rectal cancer; apparent diffusion coefficient (ADC); chemoradiation; histogram; magnetic resonance imaging (MRI)