Effect of EGFR amplification on the prognosis of EGFR-mutated advanced non-small-cell lung cancer patients: a prospective observational study

Background: Epidermal growth factor receptor (EGFR) amplification refers to the copy number increase of EGFR gene, and is often identified as a "bypass " way of Epidermal growth factor receptor Tyrosine kinase inhibitors (EGFR-TKI) resistance. We aimed to explore the effect of EGFR amplification on EGFR mutation treatmentnaive advanced non-squamous non-small cell lung cancer (NSCLC) patients.Methods: We conducted a prospective observational study in single center, enrolling advanced non-squamous NSCLC patients receiving Tyrosine kinase inhibitors (TKIs) between March 3, 2019, and February 1, 2022. Next-generation sequencing (NGS) was used to detect genetic alterations in tumor tissue samples. Progression-free survival (PFS) curves were performed using the Kaplan-Meier method. Univariate and multivariate analyses were used to evaluate factors affecting the efficacy of TKIs.Results: A total of 117 treatmentnaive advanced NSCLC patients were identified in this study. EGFR amplification was found in 22 of 117 (18.8%) patients with EGFR mutations. Of 22 patients with EGFR amplification, 10 patients harbored EGFR 19 del, 11 patients with 21-L858R. The median follow-up time was 22.47 months. The median PFS of the patients with or without EGFR amplification was 8.25 months and 10.67 months, respectively (log-rank test, P = 0.63). In multivariate analysis, EGFR amplification was not an independent prognosis factor for the patients receiving first-line TKIs [HR = 1.38, 95%CI (0.73-2.58), P = 0.321]. Subgroup analysis revealed that EGFR amplification is a risk factor for progression in the brain metastasis population. [HR = 2.28, 95%CI (1.01, 5.14), P = 0.047].Conclusion: EGFR amplification is not an independent prognosis factor for PFS in advanced non-squamous NSCLC patients receiving first-line TKIs. However, it is an independent risk factor for PFS in the brain metastasis population.