P1.05-008 Detection of EGFR Mutations in Pulmonary Vein and Peripheral Blood Plasma Cell-Free DNA for Analysis of Surgical Treatment in Early-Stage NSCLC

Abstract

Free circulating DNA (cfDNA) has been known for several decades. These small DNA fragments are released into the circulation from nucleated cells through necrosis, apoptosis and/or active secretion. Use of blood plasma cfDNA to detect mutations has spread widely as a form of liquid biopsy. However, it remains unclear which types of samples are appropriate for detecting tumor cell-free DNA in these biopsies. We compared the abundance of EGFR mutations in peripheral blood and pulmonary vein plasma cell-free DNA from patients with early-stage NSCLC. In this study, primary lung tumors and matched presurgery peripheral blood plasma samples and intraoperative pulmonary vein blood samples were collected from patients with early-stage NSCLC (n=89). We detected EGFR mutations (exon19 deletion, L858R, G719X, S768I and T790M) in 89 early-stage lung cancer samples using droplet digital PCR (ddPCR) and amplification refractory mutation system (ARMS). EGFR mutation abundance was determined and analyzed to reveal potential impact of samples types. Presurgery peripheral blood plasma samples (n=89) and intraoperative pulmonary vein blood samples (n=89) matched tumor tissue samples (n=89) were analyzed for EGFR mutations using ddPCR and ARMS respectively. Of the 41 EGFR mutations detected in tumor tissues by ARMS, 37 of the corresponding mutations were detected in presurgical peripheral blood plasma cfDNA and intraoperative pulmonary vein cfDNA, whereas 4 mutations were found in plasma from patients with EGFR wild-type tumors (sensitivity 80.49%, specificity 91.67%).Free circulating DNA was identified in the plasma of pulmonary venous blood and peripheral blood in thirty-seven patients. Of the 37 cases of EGFR mutation positive plasma samples, ddPCR identified a higher mutation abundance of pulmonary venous samples than peripheral blood (1.05% vs. 0.12%, p = 0.007). This study demonstrates accurate mutation detection in plasma using ddPCR, and that cfDNA can be detected in presurgical peripheral blood and intraoperative pulmonary vein in patients with early-stage lung cancer. Our results suggest that pulmonary venous blood can be obtained from the resected specimen, thus facilitating the detection of cfDNA. Future studies can now address whether monitoring the change of EGFR mutation abundance after surgery identifies patients at risk for recurrence, which could guide therapy decisions for individual NSCLC patients.