Intraoperative spectroscopic evaluation of sentinel lymph nodes in breast cancer surgery

Abstract Purpose Sentinel lymph node (SLN) biopsy is a standard procedure for patients with breast cancer and normal axilla on imaging. Positive SLNs on histological examination can lead to a subsequent surgery for axillary lymph node clearance (ALNC). Here we report a non-destructive technique based on autofluorescence (AF) imaging and Raman spectroscopy for intra-operative assessment of SLNs excised in breast cancer surgery. Methods A microscope integrating AF imaging and Raman spectroscopy modules AF was built to allow scanning of lymph node biopsy samples (AF imaging determined optimal sampling locations for Raman spectroscopy measurements). After optimisation of the AF image analysis and training a classification models based on data from 85 samples (scanning 20–30 minutes), the AF-Raman technique was tested on an independent set of 81 lymph nodes. Sensitivity and specificity were calculated using post-operative histology as a standard of reference. Results The area under the receiver operating characteristic (ROC) curve for the AF-Raman technique was 0.93. For a regime that maximised specificity (reduce risks of false positives), an accuracy of 97% specificity and 80% sensitivity was achieved. The main confounders for SLN metastasis were areas rich in histiocytes clusters, for which only few Raman spectra had been included in the training dataset. Conclusions This preliminary study indicates that with further development and extension of the training dataset (inclusion of Raman spectra of capsule and histiocytes clusters), the AF-Raman is a promising technique for intra-operative assessment of SLNs. Intra-operative detection of positive biopsy could avoid second surgery for axillary clearance.