Using endobronchial ultrasound features to predict lymph node metastasis in patients with lung cancer

Abstract

Purposes: Reliable staging of the mediastinum determines TNM classification and directs therapy for non-small cell lung cancer (NSCLC). Our aim was to evaluate predictors of mediastinal lymph node metastasis in patients undergoing endobronchial ultrasound (EBUS).

Methods: Patients with known or suspected lung cancer undergoing EBUS for staging were included. Lymph node radiographic characteristics on chest CT/PET scan and ultrasound characteristics of size, shape, border, echogenicity, and number were correlated with rapid on-site evaluation (ROSE) and final pathology. Logistic regression (estimated with generalized estimating equations to account for correlation across nodes within patients) was used with cancer (vs normal pathology) as the outcome. ORs compare risks across groups, and testing was performed with two-sided α of 0.05.

Results: Two hundred twenty-seven distinct lymph nodes (22.5% positive for malignancy) were evaluated in 100 patients. Lymph node size, by CT scan and EBUS measurements, and round and oval shape were predictive of mediastinal metastasis. Increasing size of lymph nodes on EBUS was associated with increasing malignancy risk (P = .0002). When adjusted for CT scan size, hypermetabolic lymph nodes on PET scan did not predict malignancy. Echogenicity and border contour on EBUS and site of biopsy were not significantly associated with cancer. In 94.8% of lymph nodes with a clear diagnosis, the ROSE of the first pass correlated with subsequent passes.

Conclusions: Lymph node size on CT scan and EBUS and round or oval shape by EBUS are predictors of malignancy, but no single characteristic can exclude a visualized lymph node from biopsy. Further, increasing the number of samples taken is unlikely to significantly improve sensitivity.

Figure 1.

Station 4R (right paratracheal) lymph node, described as oval shape, 4.9-mm size, hypoechoic, well-defined border, and single (A). Edge of azygos vein shown at B. Mediastinal soft tissue shown at C.

Figure 2.

Station 7 (subcarinal) lymph node, described as round shape, 16.6-mm size, hypoechoic, poorly defined border, and single (A). Mediastinal soft tissue shown at B.