Advances in understanding the mechanisms underlying acquired resistance to third-generation tyrosine kinase inhibitors in non-small cell lung cancer.

Acquired resistance to third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) presents a formidable challenge in the treatment of non-small cell lung cancer (NSCLC). Despite the remarkable efficacy of these agents, resistance inevitably develops, typically within approximately 10 months of treatment initiation. This review elucidates the multifaceted mechanisms driving this resistance, broadly categorized into on-target EGFR-dependent alterations and off-target EGFR-independent bypass pathway activations. On-target mechanisms include the emergence of tertiary EGFR mutations, most notably C797S, which disrupts TKI binding. Off-target mechanisms encompass the activation of alternative signaling pathways such as MET and HER2/HER3 amplification, as well as histological transformations and complex changes within the tumor microenvironment. Furthermore, recent discoveries highlight the role of epigenetic dysregulation and metabolic reprogramming in fostering resistance. To counter this pervasive adaptability, advanced diagnostic methodologies, including liquid biopsy and high-resolution omics technologies, are crucial for real-time molecular profiling. The field is actively exploring emerging combination therapeutic strategies to circumvent these diverse resistance pathways, aiming to prolong clinical benefits and improve patient outcomes. The persistent emergence of resistance underscores that current targeted therapies, while revolutionary, are primarily disease-modifying rather than curative, necessitating continuous innovation to overcome the inherent biological challenge of tumor adaptability and heterogeneity.