Clinical outcomes of first-line osimertinib in NSCLC patients with EGFR mutations.

e20649 Background: Since osimertinib was approved for the first-line treatment of non-small cell lung cancer (NSCLC) indications in 2019, its utilization rate in first-line therapy has been increasing. At present, the number of observational studies focusing on osimertinib's application in the first-line treatment of EGFR-mutated NSCLC patients in China remains relatively scarce. This study aimed to retrospectively analyze the efficacy and safety profiles of first-line osimertinib in EGFR-mutated NSCLC and explore the factors that could potentially influence the prognosis of these patients. Methods: This single-center study recruited Chinese patients with EGFR-mutated NSCLC treated with first-line osimertinib from January 2019 to December 2022. The primary endpoint was progression-free survival (PFS). Efficacy data for the overall and subgroups population were analyzed by the Kaplan-Meier method. Factors influencing PFS were analyzed by the univariate and multivariate Cox regression models, with restricted mean survival time (RMST) applied for additional analysis. Finally, the safety patterns of the overall population were also described. Most statistical analyses were done with Stata version 17.0, while some data pre-processing and visualization were performed using R version 4.3.1. Results: A total of 74 patients were included in this study. The median follow-up time was 17.1 months (95% CI: 14.1-21.2 months). The median PFS for the overall population was 16.3 months (95% CI: 13.2-20.3 months). Within the subset of disease stages, patients with stage IIIA/IVA exhibited a significantly longer median PFS than those with stage IVB (25.1 vs. 15.0 months, p =0.035). Patients with a prognostic nutritional index (PNI) ≥39.4 had a significantly longer median PFS than those with a PNI<39.4 (17.2 vs. 10.7 months, p =0.030). Patients with 19del mutation had a longer median PFS than those with L858R or other complex mutations (25.1 vs. 16.2 vs. 15.0 months, p =0.435), although the difference was not significant. Cox regression analysis showed that disease stage and PNI were independent factors associated with disease progression of first-line osimertinib. Patients with stage IVB or PNI<39.4 at baseline had a higher risk of progression when receiving first-line osimertinib. The restricted mean survival time (RMST) analysis indicated that patients with a high PNI showed a 1.5-months prolongation of PFS compared to those with a low PNI from the initiation of treatment to 13.6 months ( p =0.116). Regarding safety, the common adverse events (AEs) were rash, oral mucositis, diarrhea, decreased white blood cell counts, and paronychia, among which most were grades 1-2. Conclusions: The efficacy of first-line osimertinib is favorable, and most AEs were grades 1-2. Disease stage and PNI at baseline were independent factors associated with disease progression in NSCLC patients receiving first-line osimertinib.