A Comprehensive Review of Epidermal Growth Factor Receptor Mutation Abundance in Non-Small Cell Lung Cancer Treated with Tyrosine Kinase Inhibitors.

\n<bold><italic>Background:</italic></bold> Lung cancer is a major contributor to cancer-related death worldwide. Non-small cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancers. Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are currently viewed as the established first-line therapy for patients with advanced NSCLC with EGFR mutations. <bold><italic>Summary:</italic></bold> The potential predictive value of the quantitative abundance of epidermal growth factor receptor (EGFR) mutations in the treatment of NSCLC is widely recognized and regarded as a significant indicator. The definition of mutation abundance in the EGFR gene in most current studies is mainly calculated based on the ratio of mutation to wild-type gene copy number or based on the ratio of allele number; for example, variant allele frequency is the ratio of the number of mutant alleles to the total number of alleles at a particular locus. Results of the included primary studies are as follows. (1) Significant association between EGFR mutation abundance and progression-free survival (PFS): median PFS was significantly longer in the high abundance group (11.0 months, 95% CI: 9.7–12.3 months) than in the low abundance group (5.3 months, 95% CI: 3.6–7.0 months) in the study by Liu et al. High mutation abundance (HR: 0.77, 95% CI: 0.66–0.82, <italic>p</italic> = 0.037) was an independent prognostic determinant of PFS in the study by Wang et al. Among patients receiving EGFR-TKI as first-line therapy, the median PFS was significantly longer in the high mutation abundance group than in the low mutation abundance group (12.7 months vs. 8.7 months, <italic>p</italic> = 0.002). EGFR mutation abundance ≥30% was an independent risk factor for PFS (HR: 1.64, 95% CI: 1.17–2.31). (2) Significant association between EGFR mutation abundance and overall survival (OS): the median OS in the high abundance group in the study by Liu et al. was 20.9 months (95% CI: 18.3–23.5 months), while that in the low abundance group was 13.0 months (95% CI: 10.0 months) (95% CI: 10.3–15.7 months); longer OS was independently associated with high mutation abundance (HR: 0.62, 95% CI: 0.50–0.79, <italic>p</italic> = 0.027). <bold><italic>Key Messages:</italic></bold> The objective of this article was to conduct a comprehensive examination and analysis of the association between the abundance of EGFR mutations in NSCLC and the effectiveness of treatment with TKIs while also considering the development of drug resistance. The potential predictive value of epidermal growth factor receptor (EGFR) mutation abundance in treating non-small cell lung cancer (NSCLC) is widely recognized. The definition of EGFR gene mutation abundance in most current studies is mainly calculated based on the ratio of the mutation to the wild-type gene copy number or the ratio of the allele number. This article reviewed relevant literature by reviewing EGFR mutation abundance and tyrosine kinase inhibitors (TKIs) treatment efficacy and drug resistance in NSCLC. <italic><bold>Conclusion:</bold></italic> The specific type and abundance of EGFR mutations may affect the therapeutic efficacy, quality of life, and prognosis in NSCLC patients treated with first-line TKIs. Moreover, the abundance of EGFR mutations significantly correlates with progression-free survival and overall survival. Monitoring dynamic changes in EGFR abundance is critical for the early identification of TKI effectiveness, resistance, and prognosis. [ABSTRACT FROM AUTHOR]