title: Ex vivo sentinel lymph node mapping in colorectal cancer using a magnetic nanoparticle tracer to improve staging accuracy: a pilot study.
abstract: OBJECTIVE
  Nodal status is the most important prognostic factor in colorectal cancer (CRC). Small occult metastases may remain undetected on conventional histopathological examination, potentially resulting in undertreatment. Ex vivo sentinel lymph node mapping (SLNM) can be used to improve the accuracy of nodal staging, but the currently used tracers suffer from drawbacks, which hamper implementation of the technique in routine clinical practice. Magnetic tracers are the optimal size for sentinel lymph node (SLN) retention and allow objective quantitative selection of SLNs; they therefore have great potential for SLNM in CRC. The study evaluates the feasibility of ex vivo magnetic SLNM and compares the performance of this technique with blue dye SLNM.
  
  
  METHODS
  Twenty-eight ex vivo SLNM procedures were performed in 27 histological node-negative patients with CRC using a magnetic tracer and blue dye. A magnetometer was used to select magnetic SLNs after formalin fixation of the CRC specimen. Both magnetic and blue SLNs were subjected to serial sectioning and immunohistochemical staining to reveal occult metastases.
  
  
  RESULTS
  At least one SLN was successfully identified in 27/28 (96%) and 25/28 (89%) of the cases with the magnetic technique and blue dye. Isolated tumour cells were detected in 10 patients. This was predicted with 100% sensitivity and accuracy using the magnetic technique, and with 91% sensitivity and 96% accuracy using the blue dye technique.
  
  
  CONCLUSIONS
  This study demonstrates that ex vivo magnetic SLNM is a feasible technique for use in routine clinical practice, improving nodal staging accuracy of CRC patients.
authors.affiliation: MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands.
authors.forename: J J
authors.identifier: http://orcid.org/0000-0003-4401-5768
authors.initials: JJ
authors.lastname: Pouw
authors.affiliation: MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands.|Department of Surgery, Medisch Spectrum Twente, Enschede, The Netherlands.
authors.forename: M R
authors.initials: MR
authors.lastname: Grootendorst
authors.affiliation: Department of Surgery, Medisch Spectrum Twente, Enschede, The Netherlands.
authors.forename: J M
authors.initials: JM
authors.lastname: Klaase
authors.affiliation: Laboratorium Pathologie Oost Nederland, Hengelo, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: van Baarlen
authors.affiliation: MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands.
authors.forename: B
authors.initials: B
authors.lastname: Ten Haken
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D005240:Feasibility Studies; D005260:Female; D005557:Formaldehyde; D006801:Humans; D008207:Lymphatic Metastasis; D058185:Magnetite Nanoparticles; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D010865:Pilot Projects; D000071036:Sentinel Lymph Node / Q000000981:diagnostic imaging / Q000473:pathology*; D021701:Sentinel Lymph Node Biopsy / Q000379:methods*
chemical_list: D058185:Magnetite Nanoparticles; D005557:Formaldehyde
keywords: Superparamagnetic iron oxide; colorectal cancer; magnetic tracer; sentinel lymph node mapping; staging