Intraoperative spectroscopic evaluation of sentinel lymph nodes in breast cancer surgery

Background: Sentinel lymph node (SLN) biopsy is a standard procedure for patients with breast cancer. Positive SLNs on histological examination can lead to a second 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 was built to allow scanning of lymph node biopsy samples. AF imaging was utilised to determine optimal sampling locations for Raman spectroscopy measurements, such that scanning was completed within 20-30 minutes. After optimisation of the AF image analysis and training of classification models based on data from 85 samples, 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 analysis for bisected lymph nodes was 0.93. For a regime that maximised specificity (reduced risk of false positive detections), a 97% specificity and a 80% sensitivity was achieved. The main confounders for metastasis were areas rich in histiocytes, 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 histiocytes), the AF-Raman is a promising technique for intra-operative assessment of SLNs. Intra-operative detection of metastatic SLNs could greatly reduce additional surgery for axillary clearance.