Validation of Liquid Biopsy Assay of EBUS-TBNA Supernatant Fluid for Diagnosing Lung Cancer: a Feasibility Study

Background Lung cancer is the leading cause of cancer deaths. In particular, non-small cell lung cancers (NSCLC) accounts for over 80% of cases. Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is the first-choice procedure for staging of NSCLC, as it allows a low-risk, minimally invasive histopathological tumor diagnosis, and provides adequate material for immunohistochemistry staining and molecular testing. During the procedure, thoracic lymph nodes are sampled under endobronchial sonographic guidance. However, 10-15% of EBUS-TBNA does not yield adequate cytological material for precise diagnosis, staging, or further testing. This may result from sampling errors, low quality or quantity of collected material, or abundance of necrosis. In those cases, further invasive surgical procedures such as mediastinoscopy or thoracoscopy may be considered to complete the staging determination.

Next generation sequencing (NGS) of tumor cells is recommended to identify molecular alterations to select targeted therapies and improve outcomes. When tissue samples are limited or non-diagnostic, NGS can also be performed on peripheral blood or other body fluids, such as malignant pleural effusions and EBUS-TBNA supernatant, by liquid biopsy (LB) technics. Molecular profiling of peripheral blood by LB is highly concordant with NGS of tissue biopsies, the same mutations are detected by both methods, and is thus gaining an increasing popularity in the management of patients with NSCLC. LB can provide a molecular characterization when tissue quality or quantity is not sufficient, identify possible therapeutic targets when such are not detected by tissue NGS, and guide further treatment in cases of disease progression. LB NGS of EBUS-TBNA supernatant was assessed in several small-scale studies, which found good concordance with NGS of tissue biopsies and peripheral blood, improved failure rates, and possibly reduced costs and turnaround times. Those studies included supernatant from positive procedures only, that is, procedures in which tumor cells were identified from EBUS-TBNA samples. Currently, LB NGS cannot ascertain (or rule-out) lymph nodes involvement in tumor development, and thus cannot contribute to the staging process.

This study aim is to preliminary assess whether LB NGS from the supernatant could contribute to identifying lymph nodes involvement in subjects diagnosed with NSCLC, but determined as negative for lymph nodes involvement by EBUS-TBNA.

The study hypothesis is that there is an excellent correlation between LB NGS from EBUS-TBNA supernatant and tumor involvement of the lymph nodes, even when such involvement is unrecognized by EBUS-TBNA cytology.

Study Objectives General Aim To preliminary assess whether LB NGS of the supernatant may be indicative of lymph node involvement in patients with non-small cell lung cancer (NSCLC) in whom no tumor cells have been identified in the aspirate (false negative).