Reliable staging of the mediastinum is essential to determine TNM classification and direct appropriate therapy for non-small cell lung cancer (NSCLC). The use of endobronchial ultrasound (EBUS) as a diagnostic tool to stage lung cancer is increasing. The purpose of this study was to evaluate the predictors of malignancy in patients undergoing EBUS.
Patients with known or suspected lung cancer undergoing EBUS-FNA for staging purposes who had PET-CT scan performed were included. Ultrasound characteristics of size, shape (round, oval, triangular, draping), border (well-defined, indistinct), echogenicity (hyperechoic, hypoechoic), and number of nodes at each station were recorded and correlated with ROSE (rapid on-site evaluation) and final pathology. Logistic regression was used with cancer outcome. Generalized estimating equations were used to account for correlation across nodes within the same patient. Odds ratios were used to compare risks across groups and two-sided Wald tests were used with an alpha of 0.10.
Fifty-six distinct nodes (28.6% were positive for malignancy) were evaluated in 29 patients. Of the characteristics assessed, size and shape were the only factors predictive of metastasis in mediastinal lymph nodes. Increasing size of lymph nodes on EBUS correlated with increasing odds of malignancy (p = 0.06). Nodes larger than 40mm were more likely to be malignant than nodes smaller than 20mm (OR=3.84, p = 0.09). Round shape was more likely to be malignant than triangular shaped nodes (OR=9.09, p = 0.04). Echogenicity and border were not significantly associated with cancer. In 53 of 56 (94.6%) of lymph nodes, the ROSE of the initial sampling pass was consistent with the final pathology.
Shape and size of lymph nodes on ultrasound are predictors of malignancy. Correlation with imaging characteristics (e.g. PET-CT) and increasing the sample size may improve the prediction model. However, increasing the number of samples taken is unlikely to improve sensitivity.
Currently there is no way to recommend which lymph nodes should be biopsied in cases of known or suspected lung cancer. This study supports the routine biopsy of all lymph nodes.
Jessica Wang, No Financial Disclosure Information; No Product/Research Disclosure Information