The value of shear wave elastography in predicting for undiagnosed small cervical lymph node metastasis in nasopharyngeal carcinoma: A preliminary study.

Background: To investigate the diagnostic value of shear wave elastography (SWE) in identifying cervical small lymph node metastases in nasopharyngeal carcinoma (NPC) patients.

Materials And Methods: This prospective study was approved by the local institutional review board. From July 2014 to March 2016, 114 sLNs from 62 newly diagnosed NPC patients (47 men, 15 women) were assessed. Target small lymph nodes (sLNs), which were undiagnosed by magnetic resonance imaging (MRI), were defined as scattered cervical lymph nodes that had no evidence of central necrosis or extracapsular spread and exhibited a maximum transverse diameter ≥5 mm and <10 mm in MRI. The mean (Emean), minimum (Emin) and maximum (Emax) of the elasticity indices (EIs) were measured by SWE at the stiffest part of the sLN (kPa). Biopsy pathology was served as the reference standard. Diagnostic performances were assessed using receiver operating curve (ROC) analysis on a node-by-node basis.

Results: Of the 114 small cervical lymph nodes, 88 (77.2%) were benign, and 26 (22.8%) were malignant. All SWE EIs were significantly higher in malignant sLNs than in benign sLNs (p < 0.001). Emean exhibited the highest diagnostic value (area under the curve = 0.879 ± 0.036) (p < 0.001) and the corresponding sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 84.6%, 83.0%, 59.5%, 94.8% and 83.3%, respectively. The intra-observer reproducibility of all SWE EIs were significant, with intra-class correlation coefficient (ICC) of 0.745 in Emean, 0.716 in Emax and 0.702 in Emin.

Conclusion: Shear wave elastography is an optional supplementary imaging modality to routine MRI examination to diagnose cervical lymph nodes in NPC patients.