title: Magnetization transfer imaging to assess tumour response after chemoradiotherapy in rectal cancer.
abstract: OBJECTIVE
  Single-slice magnetization transfer (MT) imaging has shown promising results for evaluating post-radiation fibrosis. The study aim was to evaluate the value of multislice MT imaging to assess tumour response after chemoradiotherapy by comparing magnetization transfer ratios (MTR) with histopathological tumour regression grade (TRG).
  
  
  METHODS
  Thirty patients with locally advanced rectal cancer (cT3-4 and/or cN2) underwent routine restaging MRI 8 weeks post-chemoradiotherapy, including multislice MT-sequence, covering the entire tumour bed. Two independent readers delineated regions of interest on MTR maps, covering all potential remaining tumour and fibrotic areas. Mean MTR and histogram parameters (minimum, maximum, median, standard deviation, skewness, kurtosis, and 5-30-70-95th percentiles) were calculated. Reference standard was histological TRG1-2 (good response) and TRG3-5 (poor response).
  
  
  RESULTS
  24/30 patients were male; mean age was 67.7 ± 10.8 years. Mean MTR rendered AUCs of 0.65 (reader1) and 0.87 (reader2) to differentiate between TRG1-2 versus TRG3-5. Best results were obtained for 95(th) percentile (AUC 0.75- 0.88). Interobserver agreement was moderate (ICC 0.50) for mean MTR and good (ICC 0.80) for 95(th) percentile.
  
  
  CONCLUSIONS
  MT imaging is a promising tool to assess tumour response post-chemoradiotherapy in rectal cancer. Particularly, 95(th) percentile results in AUCs up to 0.88 to discriminate a good tumour response.
  
  
  CONCLUSIONS
  • The mean MTR can differentiate between good and poor responders after chemoradiation. • In addition to measurement of the mean value, histogram analyses can be beneficial. • The histogram parameter 95 (th) percentile can reach AUCs of 0.75-0.88.
authors.affiliation: Department of Radiology, Maastricht University Medical Center, PO Box 5800, 6202 AZ, Maastricht, The Netherlands.|Department of Surgery, Maastricht University Medical Center, Maastricht, The Netherlands.|GROW School of Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Milou H
authors.initials: MH
authors.lastname: Martens
authors.affiliation: Department of Radiology, Maastricht University Medical Center, PO Box 5800, 6202 AZ, Maastricht, The Netherlands.
authors.forename: Doenja M J
authors.initials: DM
authors.lastname: Lambregts
authors.affiliation: N. Papanikolaou and Associates LLC, Heraklion, Greece.
authors.forename: Nickolas
authors.initials: N
authors.lastname: Papanikolaou
authors.affiliation: N. Papanikolaou and Associates LLC, Heraklion, Greece.
authors.forename: Styliani
authors.initials: S
authors.lastname: Alefantinou
authors.affiliation: Department of Radiology, Maastricht University Medical Center, PO Box 5800, 6202 AZ, Maastricht, The Netherlands.
authors.forename: Monique
authors.initials: M
authors.lastname: Maas
authors.affiliation: Computational Medicine Laboratory, Institute of Computer Science, Foundation for Research and Technology, Hellas, Greece.
authors.forename: Georgios C
authors.initials: GC
authors.lastname: Manikis
authors.affiliation: Computational Medicine Laboratory, Institute of Computer Science, Foundation for Research and Technology, Hellas, Greece.
authors.forename: Kostantinos
authors.initials: K
authors.lastname: Marias
authors.affiliation: Department of Pathology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Riedl
authors.affiliation: Department of Surgery, Maastricht University Medical Center, Maastricht, The Netherlands.|GROW School of Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Geerard L
authors.initials: GL
authors.lastname: Beets
authors.affiliation: Department of Radiology, Maastricht University Medical Center, PO Box 5800, 6202 AZ, Maastricht, The Netherlands. beetstan@me.com.|GROW School of Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands. beetstan@me.com.
authors.forename: Regina G H
authors.initials: RG
authors.lastname: Beets-Tan
mesh_terms: D000368:Aged; D059248:Chemoradiotherapy / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D017564:Radiation Pneumonitis / Q000473:pathology*; D012004:Rectal Neoplasms / Q000473:pathology* / Q000628:therapy*; D015203:Reproducibility of Results; D012189:Retrospective Studies
keywords: Interobserver agreement; Magnetization transfer imaging; Rectal cancer; Response assessment; Tumour regression grade