Post-Progression Management, Resistance Mechanisms, and Future Directions in EGFR-Mutated NSCLC

Dr. Herbst identifies post-progression management as the central ongoing challenge in EGFR-mutated NSCLC: even with highly effective first-line targeted therapy, median duration of response in the metastatic setting is approximately 22 to 24 months, and the disease invariably acquires resistance. Dr. Kareff describes his systematic approach to progression: both solid tissue biopsy from the progressing lesion and repeat liquid biopsy are performed simultaneously, serving different but complementary purposes. Solid tissue biopsy is necessary to rule out small cell transformation, which occurs in a meaningful subset of patients with EGFR-mutated NSCLC at progression and requires a fundamentally different chemotherapy-based treatment approach, often while maintaining TKI therapy. Liquid biopsy identifies the dominant molecular mechanism of resistance, with clinically actionable findings including MET exon 14 skipping mutations, for which retrospective data support combining osimertinib with a MET inhibitor; MET amplification; secondary EGFR mutations; and acquisition of RB1 or TP53 co-mutations suggesting small cell transformation.

Dr. Kareff highlights that the co-inhibition of EGFR and MET by amivantamab is directly relevant for patients who progress on osimertinib with MET amplification as the dominant mechanism and discusses the potential role of amivantamab-based combinations in this context for patients who have not yet received them. He describes the field as rapidly evolving, requiring dedicated thoracic oncology specialists to stay current with resistance mechanism data.

Dr. Kareff closes by calling attention to leptomeningeal disease in EGFR-mutated NSCLC as an underappreciated and clinically challenging subset: strategies including high-dose osimertinib (dose escalation to improve CNS penetrance) and novel combinations are under investigation, but significant unmet need remains. Dr. Herbst adds that immunotherapy combinations, including cancer vaccines, represent an exciting longer-term frontier. Both panelists express optimism about the continued evolution of treatment across the full EGFR-mutated NSCLC continuum, from early-stage adjuvant through perioperative and metastatic disease management.