Liquid Biopsy Assay of EBUS-TBNA Supernatant Fluid for Diagnosing Lung Cancer

Background and aim: Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is the gold standard of lung cancer staging, yet up to 15% of procedures produce inadequate samples for definite diagnosis or staging. In such cases, more invasive surgical procedures are usually considered. Fluid collected during EBUS-TBNA is centrifuged to produce a pellet for cell block histopathological examination , while the supernatant is usually discarded. It has been demonstrated that this supernatant can provide material for next generation sequencing (NGS) mutation analysis using liquid biopsy (LB) technics when the procedure yielded positive results (tumor cells were demonstrated in the aspirate). We wish to assess whether LB NGS of the supernatant may provide data regarding lymph nodes involvement in non-small cell lung cancer (NSCLC) in cases with a negative EBUS-TBNA evaluation (no tumor cell identified in the aspirate). Methods: A prospective feasibility study which will recruit participants with high suspicion for thoracic lymph nodes involvement in NSCLC who will be subjected to EBUS-TBNA. The final study group will comprise of 10 subjects with a negative EBUS-TBNA evaluation (no tumor cell detected) who will require surgical resection of the thoracic lymph nodes. EBUS-TBNA collected fluid will be centrifuged and separated. Cellular pellets will undergo cytological and histopathological evaluation, including tissue NGS, as usual. Cell-free DNA will be extracted from the supernatant and will undergo separate LB NGS targeted to genes frequently mutated in NSCLC. We will assess the concordance between the positivity of supernatant NGS and surgical lymph nodes staging, and the concordance between supernatant NGS and blood NGS. Expected results: We expect high concordance between surgical lymph nodes staging and supernatant NGS, that is, genetic mutations would be identified by the supernatant NGS in subjects with lymph nodes involvement by tumor, and not in those without it. Importance to Medicine: NSCLC is the leading cause of cancer mortality. Improving the effectiveness of EBUS-TBNA may reduce the need for additional invasive procedures, increase accuracy and reduce turnaround time of specimens.