Intraoperative identification and analysis of lymph nodes at laparoscopic colorectal cancer surgery using fluorescence imaging combined with rapid OSNA pathological assessment

Intraoperative identification and analysis of lymph nodes at laparoscopic colorectal cancer surgery using fluorescence imaging combined with rapid OSNA pathological assessment Trevor M. Yeung 0 1 2 3 4 Lai Mun Wang 0 1 2 3 4 Richard Colling 0 1 2 3 4 Rebecca Kraus 0 1 2 3 4 Ronan Cahill 0 1 2 3 4 Roel Hompes 0 1 2 3 4 Neil J. Mortensen 0 1 2 3 4 0 Department of Colorectal Surgery, Oxford University Hospitals NHS Foundation Trust , Oxford , UK 1 Nuffield Department of Surgical Sciences, University of Oxford , Oxford OX3 9DU , UK 2 & Trevor M. Yeung 3 Mater Misericordiae University Hospital and UCD School of Medicine & Medical Science , Oxford , UK 4 Department of Cellular Pathology, Oxford University Hospitals NHS Foundation Trust , Oxford , UK Background Standard surgical practice for colorectal cancer involves resection of the primary lesion and all draining lymph nodes. Accurate intraoperative assessment of nodal status could allow stratified resectional extent. One-step nucleic acid (OSNA) can provide a rapid method of interrogating nodal tissue, whilst near-infrared (NIR) laparoscopy together with indocyanine green (ICG) can identify relevant nodal tissue intraoperatively. Methods ICG was administered around the tumour endoscopically prior to the operation. Fluorescent nodes identified by NIR were marked and submitted for whole-node OSNA analysis. Further fresh lymph nodes dissected from the standard resection specimen were examined and analysed by both conventional histology and OSNA. In addition, the status of the fluorescent nodes was compared to that of non-ICG nodes to assess their predictive value. Results Sixteen patients were recruited with a total final lymph node count of 287. 78 fresh lymph nodes were identified on fresh dissection for both histological and OSNA assessment with an analytical concordance rate of 98.7% (77/78). OSNA sensitivity was 1 (0.81-1, 95% CI) and specificity 0.98 (0.91-1, 95% CI). Six patients had a total of nine nodes identified intraoperatively by ICG fluorescence. Of these nine nodes, one was positive for metastasis on OSNA. OSNA analysis of the ICG-labelled node matched the final histological nodal stage in 3/6 patients (two being N0 and one N1). The final pathological nodal stage of the other three was N1 or N2, while the ICG nodes were negative. Conclusion OSNA is highly concordant with standard histology, although only a minority of nodes identifiable by full pathological analysis were found for OSNA on fresh dissection. OSNA can be combined with NIR and ICG lymphatic mapping to provide intraoperative assessment of nodal tissue in patients with colorectal cancer. Colorectal; Lymph Node; Fluorescence; OSNA; Imaging - Currently, the standard operation for colorectal cancer involves the excision of the primary lesion together with all its draining lymph nodes, although there is no treatment benefit from the removal of normal (i.e. tumour negative) lymph nodes. Colorectal cancer screening programmes mean many patients are diagnosed with true early stage (i.e. N0) disease. Recently, extended lymphadenectomy has been proposed for colonic cancers, while others are considering lateral iliac nodal clearance for selected patients with rectal cancer. A facility to confidently assign nodal status intraoperatively independent of the performance of the radical resection could allow stratification of operative extent by disease stage without compromising prognostic or therapeutic value. One-step nucleic acid amplification (OSNA) is a rapid mRNA assay that can detect colorectal micrometastases in lymph nodes based on cytokeratin 19 (CK19) levels within 20 min of their removal [ 1–3 ]. Although its use to date has predominantly been from the perspective of entire node basin assessment, its technical capability provides results within a timeframe that could guide intraoperative decision making. OSNA requires fresh nodal tissue; therefore either the entire nodal basin needs removal for fresh tissue dissection or a selective, representative amount of nodal tissue may be identified by the surgeon. Our group and others have previously demonstrated that peritumoral submucosal injection of indocyanine green (ICG) with near-infrared (NIR) laparoscopy provides lymph node visualisation during colorectal cancer resections [ 4–6 ]. However, the pathological relevance of these fluorescent lymph nodes is currently not clear. This pilot study assesses the concordance between standard histology and OSNA for the analysis of lymph nodes in combination with NIR lymphangiography as proof-of-principle that current technology can support focused intraoperative node interrogation. As large patient numbers are needed for definitive conclusions, this work aimed to clarify the necessary protocols and thresholds to inform a definitive trial. Methods This was an open label, prospective trial assessing the feasibility of using OSNA analysis of fresh lymph nodes in combination with ICG and NIR f (...truncated)