Clinical Factors Affecting the Response to Osimertinib in Non-Small Cell Lung Cancer Patients with An Acquired Epidermal Growth Factor Receptor T790M Mutation: A Long-Term Survival Analysis

Background Osimertinib is a standard therapy for advanced non-small cell lung cancer (NSCLC) patients with an acquired epidermal growth factor receptor (EGFR) T790M mutation; however, the exploration of clinical characteristics that may affect prognosis and long-term survival is still lacking. Objective This retrospective study aimed to provide long-term survival data and explore meaningful prognostic factors in patients treated with osimertinib. Patients and Methods A total of 246 patients with acquired EGFR T790M mutation who were treated with osimertinib were included in this study. Progression-free survival (PFS), overall survival from osimertinib initiation (OS1), overall survival from diagnosis of advanced disease (OS), and possible prognostic clinical features were analyzed. Results The median PFS, OS1, and OS values were 12.17, 24.33, and 47.86 months, respectively. The median PFS of patients harboring EGFR exon 19 deletions/T790M (19del/T790M) and those harboring EGFR 21 L858R/T790M were 13.27 and 9.77 months ( p = 0.001), respectively, while the median OS1 values were 25.03 and 18.30 months ( p = 0.023), respectively; however, no significant difference was found in median OS ( p = 0.060). Cox regression analysis revealed that coexisting mutation type and extrathoracic metastasis affected survival (PFS, OS1). In addition, gene biopsy specimen type (tissue or blood sample) was related to PFS ( p = 0.032), which implied that liquid biopsy may be an independent poor prognostic factor. Conclusions This is the first reported survival analysis of osimertinib-treated Chinese patients, which indicates a median OS of 47.86 months. The EGFR T790M mutation is likely to coexist with 19del and indicate longer PFS and OS1 than EGFR 21 L858R/T790M. Additionally, the extrathoracic metastasis status and biopsy specimen type might also affect the survival of patients treated with osimertinib.