Multi-gene Liquid Biopsy to Detect Resistance to First-line Osimertinib in Patients With EGFR -mutated Lung Adenocarcinoma

Background/Aim: Osimertinib is currently used as a first-line treatment for EGFR-mutated non-small cell lung cancer, and the emergence of drug resistance poses a substantial challenge. Liquid biopsy with a multi-gene panel can examine both the molecular mechanisms and possibility of early resistance diagnosis. Patients and Methods: We used a molecular barcode library construction kit (Archer (R) LiquidPlexTM) that allowed the analysis of multiple cancer-related genes using cell-free DNA from the plasma samples of patients. We collected plasma from 17 consecutive patients with lung adenocarcinoma at our hospital at various time points and cell-free DNA was extracted and subjected to LiquidPlex analysis. Results: Plasma DNA concentration was not associated with the presence or absence of resistance to osimertinib. The pathological mutations detected using next -generation sequencing in the resistant specimens were in MAP2K1, PIK3CA, TP53, BRAF, and EGFR. Among the recurrent cases, EGFR mutations identified at the initial diagnosis were detected within 6 months before relapse confirmation in four cases (average 88 days). Many of the recurrent cases without detection of known EGFR mutations in the liquid biopsy showed a longer interval between the detection of relapse and the last blood draw for the liquid biopsy (average 255 days). Conclusion: Frequent liquid biopsies are useful for identifying known EGFR mutations as markers for early detection of relapse. Several cancer driver mutations were observed, suggesting a variety of mechanisms of resistance in first-line osimertinib-treated lung adenocarcinoma.