title: Pancreatic neuroendocrine tumour: Correlation of apparent diffusion coefficient or WHO classification with recurrence-free survival.
abstract: OBJECTIVE
  To evaluate the correlation between grade of pancreatic neuroendocrine tumours (pNETs) based on the 2010 World Health Organization (WHO) classification and the apparent diffusion coefficient (ADC), and to assess whether the ADC value and WHO classification can predict recurrence-free survival (RFS) after surgery for pNETs.
  
  
  METHODS
  This retrospective study was approved by the Institutional Review Board. The requirement for informed consent was waived. Between March 2009 and November 2014, forty-nine patients who underwent magnetic resonance (MR) imaging with diffusion-weighted image and subsequent surgery for single pNETs were included. Correlations among qualitative MR imaging findings, quantitative ADC values, and WHO classifications were assessed. An ordered logistic regression test was used to control for tumour size as a confounding factor. The association between ADC value (or WHO classification) and RFS was analysed.
  
  
  RESULTS
  All tumors (n=49) were classified as low- (n=29, grade 1), intermediate- (n=17, grade 2), and high-grade (n=3, grade 3), respectively. The mean ADC of pNETs was moderately negatively correlated with WHO classification before and after adjustment for tumour size (ρ=-0.64, p<0.001 and ρ=-0.55, p=0.001 respectively). RFS was significantly associated with WHO classification (p=0.007), but not with the ADC value (p=0.569).
  
  
  CONCLUSIONS
  The ADC value of pNETs is moderately correlated with WHO tumour grade, regardless of tumour size. However, the WHO tumour classification of pNET may be more suitable for predicting RFS than the ADC value.
authors.affiliation: Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Mimi
authors.initials: M
authors.lastname: Kim
authors.affiliation: Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea. Electronic address: kaienes.kang@samsung.com.
authors.forename: Tae Wook
authors.initials: TW
authors.lastname: Kang
authors.affiliation: Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Young Kon
authors.initials: YK
authors.lastname: Kim
authors.affiliation: Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Seong Hyun
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Wooil
authors.initials: W
authors.lastname: Kwon
authors.affiliation: Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Sang Yun
authors.initials: SY
authors.lastname: Ha
authors.affiliation: Biostatics and Clinical Epidemiology Center, Samsung Medical Center, Seoul, Republic of Korea.
authors.forename: Sang A
authors.initials: SA
authors.lastname: Ji
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D018278:Carcinoma, Neuroendocrine / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D010190:Pancreatic Neoplasms / Q000473:pathology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D016019:Survival Analysis; D014944:World Health Organization; D055815:Young Adult
keywords: Apparent diffusion coefficient; Magnetic resonance imaging; Pancreatic neuroendocrine tumour; Treatment outcome; WHO classification