Combined Endosonographic Mediastinal Lymph Node Staging in Positron Emission Tomography and Computed Tomography Node-Negative Non-Small-Cell Lung Cancer in High-Risk Patients

Abstract

Positron emission tomography (PET) with computed tomography (CT) is routinely utilized to investigate lymph node (LN) metastases in non-small-cell lung cancer. However, it is less sensitive in normal-sized LNs. This study was performed in order to define the prevalence of mediastinal LN metastases discovered on combined endosonography by endobronchial ultrasound (EBUS) and endoscopic ultrasound (EUS) fine needle aspiration in patients with a radiologically normal mediastinum. This study consists of a retrospective, single-institution, tertiary care referral center review of a prospectively maintained database. Patients were identified from a cohort between January 2009 and December 2014. One hundred and sixty-one patients with biopsy-proven, non-small-cell lung cancer were identified in whom both the preendosonography CT and PET-CT were negative for mediastinal LN metastases. Combined endosonography (EBUS + EUS-FNA) was performed in all patients. Z test was used for statistical analysis. A P value of <0.05 was considered statistically significant. A total of 161 consecutive patients were included. Patients were staged if they had central tumor, tumor size >3 cm, N1 lymph node involvement on PET-CT/CT, or if there was low SUV (<2.5) in the primary tumor. A total of 416 lymph nodes were biopsied in the 161 patients using combined endosonography; 147 with EBUS and 269 with EUS. Mean and median number of lymph nodes biopsied per patient using combined EBUS/EUS was 2.5 and 3, respectively (mean and median EBUS: 0.91 and 2.5; mean and median EUS 1.6 and 3). Endosonographic staging upstaged 13% of patients with radiologically normal lymph nodes in the mediastinum, hilum, lobar, and sublobar regions (confidence interval 8.22-19.20). Twenty-one out of 161 patients (13%) with radiologically normal mediastinum were positive on combined EBUS/EUS staging. Out of 21 patients upstaged on endosonography, 15 (71%) had tumor size >3 cm. Six (28%) had occult N1 disease. Thirteen (61%) had occult N2 disease and 2 (9%) had adrenal involvement. None of the upstaged patients had N1 LN involvement on PET-CT or CT scan. Combined endosonographic lymph node staging should be considered in the pretreatment staging of high-risk patients with non-small-cell lung cancer in the presence of radiologically normal mediastinal lymph nodes due to the significant rate of radiologically occult lymph node metastases.

Keywords: Computed tomography; Endobronchial ultrasound; Endoscopic ultrasound; Lung cancer; Mediastinal staging; Normal mediastinum; Positron emission tomography.