Clinical-genomic characteristics in patients with EGFR-mutated non-small cell lung cancer harboring MET copy number gains after progression on EGFR-TKI: A report from LC-SCRUM-TRY.

8628 Background: MET amplification (amp) account for 10-15% of resistance mechanism in EGFR-mutated non-small cell lung cancer (NSCLC) to EGFR-tyrosine kinase inhibitor (TKI) treatment. MET copy number (CN) gains consists of MET focal amp and polysomy (poly), but the clinical characteristics and outcome of EGFR-TKI resistant NSCLC patients harboring MET amp, poly remains unclear. Methods: The clinical-genomic characteristics and treatment outcome ofEGFR-TKI resistant EGFR-mutated NSCLC registered in LC-SCRUM-TRY (UMIN000041957) were analyzed. Genetic resistant alterations were screened using next-generation sequencing (NGS) (Tissue; Oncomine Precision Assay OPA or Plasma; Guardant360 G360), and MET-fluorescence in-situ hybridization (FISH). MET amp was defined as MET CN ≥4 (OPA), MET CN ≥2.12 (G360) or MET/CEP7 ratio ≥2 (FISH). MET poly was defined as MET CN≥5 and MET/CEP7 ratio <2 by FISH. Results: A total of 1559 patients had been enrolled in LC-SCRUM-TRY between Sep 2020 and Jan 2024. Of 1537 analyzed samples, 666 (43%) were EGFR-TKI resistant samples. Of these, 92 (14%), 239 (36%) and 335 (50%) had MET amp, poly, and no CN gain (no CNG), respectively. Patient characteristics and treatment outcome with 1 st line EGFR-TKI and platinum-based chemotherapy (PBC) post EGFR-TKI is summarized (Table 1). The overall response rate (ORR) of PBC post EGFR-TKI in the patients with MET amp, poly and no CNG was 41%, 29% and 31%, respectively (p=0.34), with median progression-free survival (mPFS) being 5.7 months, 6.8 months, and 6.7 months (p=0.02). In addition, 12 and 11 of patients with MET amp and poly were enrolled into clinical trial of MET-targeted therapy (MET-TKI, n=2; MET-antibody-drug conjugate ADC, n=4; EGFR/MET-antibody, n=2), and MET non-targeted therapy (EGFR-TKI, n=5; other ADCs, n=10: immunotherapy; n=1). The ORR of MET-targeted therapy/MET non-targeted therapy were 60/0% for MET amp, and 0/33% for MET poly, respectively. Conclusions: Patients with shorter PFS with prior 1 st line EGFR-TKI are more likely to have MET amp. The efficacy of standard PBC post EGFR-TKI in patients with MET CNG is limited. Current MET-targeted therapy may not be effective for EGFR-mutated NSCLC harboring MET poly after progression on EGFR-TKI. Table: see text