Role of shear wave elastography as an adjunct to axillary ultrasonography in predicting nodal metastasis in breast cancer patients with suspicious nodes.

Abstract

To evaluate the role of shear wave elastography (SWE) of suspicious axillary lymph nodes and its combination with B-mode USG in predicting nodal metastasis in breast cancer patients. Prospective observational study was performed from June 2018 to August 2020 on breast cancer patients with suspicious axillary nodes on USG. B-mode features (cortical thickness, effacement of fatty hilum, non-hilar blood flow and round shape) and SWE parameters (Emax, Emin, Emean and ESD) of the node with the thickest cortex were evaluated. Diagnostic performances of USG, SWE and their combination were estimated using pathological status of the node on biopsy as the gold standard. Of the 54 patients evaluated, optimal elasticity maps were obtained in 49 nodes of 49 patients (mean age, 46.3 ± 12.1 years; 48/49 (98%) females). On biopsy, 38 nodes (77.6%) had metastasis, while 11 (22.4%) had reactive hyperplasia. Emax, Emin, Emean and ESD of both cortex and hilum were significantly higher in metastatic than reactive nodes. Emax (cortex) ≥14.9 kPa had the best diagnostic performance (sensitivity, 73.7%; specificity, 81.8%). Cortical thickness ≥6.7 mm had the best diagnostic performance among B-mode features (sensitivity, 89.5%; specificity, 72.7%). Combining cortical thickness with effacement of fatty hilum and/or non-hilar blood flow yielded sensitivity of 89.5% and specificity of 90.9%. Addition of Emax (cortex) to cortical thickness and combination of ≥2 B-mode features increased their specificities to 90.9 and 100%, respectively. Metastatic axillary nodes are stiffer than reactive nodes on SWE in breast cancer patients. Emax (cortex) has the best diagnostic performance in differentiating between reactive hyperplasia and nodal metastasis. Combination of Emax (cortex) and cortical thickness increases the specificity for diagnosing metastasis, especially in nodes showing only cortical thickening. Combination of SWE and B-mode USG is highly specific for differentiating metastasis from reactive hyperplasia in suspicious nodes of breast carcinoma patients, especially in nodes with only cortical thickening.