title: DWI for Assessment of Rectal Cancer Nodes After Chemoradiotherapy: Is the Absence of Nodes at DWI Proof of a Negative Nodal Status?
abstract: OBJECTIVE
  When considering organ preservation in patients with rectal cancer with good tumor response, assessment of a node-negative status after chemoradiation therapy (CRT) is important. DWI is a very sensitive technique to detect nodes. The study aim was to test the hypothesis that the absence of nodes at DWI after CRT is concordant with a ypN0 status.
  
  
  METHODS
  A retrospective study was performed of 90 patients with rectal cancer treated with CRT followed by restaging MRI at 1.5 T, including DWI (highest b value, 1000 s/mm2). Two independent readers counted the number of nodes visible in the mesorectal compartment on DW images obtained after CRT. The number of nodes on DWI (0 vs ≥ 1) was compared with the number of metastatic nodes at histopathology or long-term clinical follow-up (yN0 vs yN-positive status).
  
  
  RESULTS
  Seventy-one patients had a yN0 status, and 19 had a yN-positive status. For 10 patients, no nodes were observed at DWI, which was concordant with a yN0 status in 100% of cases. In the other 61 patients with a yN0 status, the median number of nodes detected at DWI was three (range, 1-17 nodes). To differentiate between yN0 and yN-positive status, sensitivity was 100%, specificity was 14%, the positive predictive value was 24%, and the negative predictive value was 100%.
  
  
  CONCLUSIONS
  Although the absence of nodes at DWI is not a frequent finding, it appears to be a reliable predictor of yN0 status after CRT in patients with rectal cancer. DWI may thus be a helpful adjunct in assessing response after CRT and may help select patients for organ-saving treatment.
authors.affiliation: 1 GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands.|2 Department of Radiology, The Netherlands Cancer Institute, PO Box 90203, 1006 BE Amsterdam, The Netherlands.|3 Department of Radiology, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Miriam M
authors.initials: MM
authors.lastname: van Heeswijk
authors.affiliation: 2 Department of Radiology, The Netherlands Cancer Institute, PO Box 90203, 1006 BE Amsterdam, The Netherlands.
authors.forename: Doenja M J
authors.initials: DM
authors.lastname: Lambregts
authors.affiliation: 3 Department of Radiology, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Walter M
authors.initials: WM
authors.lastname: Palm
authors.affiliation: 3 Department of Radiology, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Babs M F
authors.initials: BM
authors.lastname: Hendriks
authors.affiliation: 2 Department of Radiology, The Netherlands Cancer Institute, PO Box 90203, 1006 BE Amsterdam, The Netherlands.|3 Department of Radiology, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Monique
authors.initials: M
authors.lastname: Maas
authors.affiliation: 1 GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands.|4 Department of Surgery, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors.forename: Geerard L
authors.initials: GL
authors.lastname: Beets
authors.affiliation: 1 GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands.|2 Department of Radiology, The Netherlands Cancer Institute, PO Box 90203, 1006 BE Amsterdam, The Netherlands.
authors.forename: Regina G H
authors.initials: RG
authors.lastname: Beets-Tan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059248:Chemoradiotherapy; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D059351:Organ Sparing Treatments / Q000379:methods; D011379:Prognosis; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000628:therapy*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D000071036:Sentinel Lymph Node / Q000000981:diagnostic imaging* / Q000473:pathology; D016896:Treatment Outcome
keywords: DWI; locally advanced rectal cancer; lymph node staging; nodal restaging; organ preservation