Real-World Analysis of the EGFR Mutation Test in Tissue and Plasma Samples from Non-Small Cell Lung Cancer

Molecular evaluation of EGFR mutation is indispensable in treating non-small cell lung cancer (NSCLC). We compared the results of EGFR analysis using tissue DNA (tDNA) and circulating tumor (ctDNA) to evaluate the feasibility of plasma as an effective material for detecting EGFR mutation and the reliability of ctDNA analysis in real-world practice settings. We enrolled 554 NSCLC cases who had undergone ctDNA EGFR analysis between January 2019 and March 2020. EGFR mutations were detected in 240 (57.3%) of the 421 cases with EGFR mutations confirmed by tDNA analysis. In multivariate analysis, the size of the largest tumor deposits, disease progression, M stage, the detectable amount of tumor tissue with EGFR mutation in distant metastasis, liver metastasis, pleural seeding, and bone metastasis (p < 0.05) were identified as independent factors affecting the detection rate of EGFR mutations in ctDNA. Survival analysis revealed ctDNA status and M stage (p < 0.001) to be independent predictors of overall survival in the multivariate analysis. Our study demonstrates that EGFR analysis using ctDNA is a useful clinical tool and can aid in therapeutic decisions in real-world practical settings. However, clinicians should be aware of the possibility of false negatives and confirm EGFR analysis using tDNA in certain situations.