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

Abstract

BackgroundMinimally 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. MethodsIn 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. ResultsIn 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. ConclusionSingle EBUS-TBNA passes yield DNA of high quantity and quality with high accuracy for molecular profiling, irrespective of tumor cell content.