Evaluating the Genomic Yield of a Single Endobronchial Ultrasound-guided Transbronchial Needle Aspiration in Lung Cancer: Meeting the Challenge of Doing More With Less

The minimum quantity of material obtained by needle-based techniques to perform genetic profiling of lung cancer remains unclear. We show that a single endobronchial ultrasound-guided needle aspiration yields sufficient DNA to support genetic analysis with high diagnostic accuracy for clinically important mutations. This has significant implications for procedural performance in lung cancer cases where genetic alterations are highly suspected. Background Minimally invasive techniques, including endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA), yield small specimens that are adequate for cytologic diagnosis of lung cancer, but also need to provide material for molecular analysis to guide treatment. The number of EBUS-TBNA passes needed for mutation testing remains unclear. We sought to assess the adequacy of a single pass for genomic profiling of actionable mutations. Methods In a prospective observational study, paired samples from the same lesion were obtained from patients undergoing EBUS-TBNA for lung cancer diagnosis/staging. Following tumor cell confirmation by rapid on-site evaluation, a “reference” sample comprising ≥ 3 passes was obtained and formalin-fixed paraffin-embedded. A “study” sample comprising a single pass was taken and snap-frozen. The primary outcome was DNA yield and quality from a single pass. The secondary outcome was diagnostic accuracy of a single pass for detecting actionable mutations. Results In 40 patients, single-pass specimens yielded a mean 3.98 μg of highly intact DNA, well above the minimum threshold for targeted sequencing, which was performed in adenocarcinoma cases (n = 24). In 23 cases, there was 100% agreement in mutation status between reference and study samples. In 1 case, the reference sample failed to generate a molecular diagnosis owing to insufficient tumor cells; however, the study specimen identified a KRAS mutation. Tumor cell percentage in mutation-positive specimens was 1% to 70%, suggesting that single-pass samples detect mutations even when tumor cell content is low. Conclusion Single EBUS-TBNA passes yield DNA of high quantity and quality with high accuracy for molecular profiling, irrespective of tumor cell content.