Abstract PS1-38: Role of MR spectroscopy in evaluation of axilla in breast cancer
Authors: Vuthaluru Srineil , Srivastava Anurag 
Published: February 2021

Abstract
The role of surgery for women with breast cancer presenting with clinically negative axilla is being questioned. Trials are underway to evaluate axillary ultrasound (AUS) for non-invasive evaluation of axilla instead of sentinel node biopsy. However, AUS has a sensitivity of 50-59%. Thus, there is a need for non-invasive test to complement AUS. MR Spectoroscopy (MRS) identifies metabolites, viz. glycerophosphocholine (GPC), phosphocholine (PC), threonine (Thr), lactate (Lac), Choline (Cho) etc that are associated with presence of metastasis in axillary lymph nodes (LN) . Biochemical changes in tumor infiltrated LNs occur earlier than morphological changes and MRS can detect these chemical changes, it can be a useful investigation in evaluation of axilla. Aim: To evaluate the role of MR Spectroscopy (MRS) in identifying biochemical changes in axillary lymph nodes in breast cancer and correlate the findings with Histopathology (HP) to predict presence of metastasis.Methods: Axillary lymph nodes were obtained from 59 patients with early breast cancer with clinically negative axilla who underwent surgery. Each LN was bisected into two equal halves. One half of LN was snap frozen in liquid nitrogen (-196°C) and then stored at −80°C until perchloric acid extraction was carried out. Other half of LN was subjected to HP evaluation with standard Eosin and Hematoxylin staining . METHOD OF MR Spectroscopy: Water-soluble metabolites from the tissue samples were extracted using PCA extraction procedure (Seenu et al Magn Reson Imaging 2005 doi: 10.1016/j.mri.2005.10.004). Proton (1H) NMR spectroscopy of specimen was performed. Concentrations of GPC, PC, Thr, Lac, Cho and other metabolites were determined by comparing the integrated intensity of isolated resonances of the compounds of interest with that of the TSP signal, correcting for the number of contributing protons and with the tissue weight . Intensity ratio for metabolites, GPC, PC and Thr (GPC+PC/Thr) was also determined.Statistical Analyses: Levels of concentrations of various metabolites were compared between involved and non-involved lymph nodes using Wilcoxon rank sum test. Diagnostic indices of MRS were assessed in terms of sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratios and overall accuracy taking final histopathology as ‘gold standard’ with 95% confidence intervals.Results: Mean concentrations of GPC, PC and Thr were significantly increased in involved as compared to non-involved node (table 1). Cho and Lac were not significantly increased. A cut-off value of 0.80 for the GPC-PC/Thr ratio was chosen to obtain a maximum accuracy of 89% based on previous study. MRS accurately predicted metastasis in 21 of the 24 patients who had LN metastasis on HP. Out of 35 patients with no LN metastasis, MRS correlated accurately with HP in 30 of them. Sensitivity, specificity, PPV, NPV and overall accuracy for MRS in detecting LN metastasis were 87.5%; 88%; 80.7%; 90.9%; and 86.4% respectively. Likelihood ratio for positive test and negative test for MRS to detect LN metastasis were 6.1 and 0.14 respectively.Conclusion: MRS can accurately predict presence of metastasis in axillary lymph nodes in vitro. In vivo studies are essential to corroborate these findings.
Mean concentrations of metabolites in axillary lymph nodesInvolvedNon involvedP valueGPC0.5923(SD=0.5726)0.3648(SD=0.6774)0.02PC0.7347(SD=0.9466)0.5286(SD=1.1111)0.03Cho0.6930(SD=0.6756)0.8435(SD=0.5030)0.21Thr2.9656(SD=2.2397)1.1674(SD=1.2274)0.02Lac4.5515(SD=2.3271)3.2907(SD=1.3296)0.31
Citation Format: Srineil Vuthaluru, Anurag Srivastava. Role of MR spectroscopy in evaluation of axilla in breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS1-38.