P3.05-012 Clinicopathological Determinants of Circulating Tumor DNA Detection in Early-Stage Non-Small Cell Lung Cancer

Circulating tumor DNA (ctDNA)-based liquid biopsies have recently demonstrated substantial promise in the diagnosis and monitoring of advanced non-small cell lung cancer (NSCLC); however, data regarding utility in early-stage (operable) disease are very limited. The aim of this study is to define the clinical feasibility of ctDNA assessment in operable NSCLC. We prospectively recruited 80 patients with clinical stage I-IIIa NSCLC undergoing curative intent tumor resection. Pre-surgical plasma cell-free DNA (cfDNA) and matched tumor genomic DNA were collected and analyzed with a novel 21-gene Digital Sequencing NGS panel (Guardant Health, Inc.) with a theoretical genomic sensitivity of >90% for NSCLC. Genomic results, including cfDNA yields, technical sequencing information, and identity and quantity of somatic variants, were correlated with various clinicopathological characteristics, including age, sex, smoking history, clinical and pathologic stage, histological tumor type, and preoperative treatment status. [Cohort enrollment and sample collection is complete. Sequencing and analysis have been completed for the first 20 patients. The remaining patients will be completed within 1-2 months. Results from the complete cohort will be updated as directed by the Core Program Committee and will include the data elements described in the methods above. A preliminary review of the data is included below.] Of the 18 patients with somatic variants detected in tumor tissue (18/20, 90%), pre-operative ctDNA was detected in 12 (67%). Pre-operative ctDNA detection was high in squamous cell carcinoma (8/8), small cell lung cancer (1/1) and mixed histology (1/1) relative to adenocarcinoma (2/10, 20%). Clinical stage did not influence detection of small cell or squamous cell carcinoma; however, no ctDNA was detected in stage I or II adenocarcinoma samples (0/5). Detailed data from the complete cohort will be submitted as a late-breaking abstract. [Conclusion to be updated pending full cohort data.] ctDNA demonstrates sufficient pre-operative clinical sensitivity to be a feasible recurrence monitoring tool but appears to be influenced by tumor type.