Patients with advanced non-small cell lung cancer with EGFR mutations in addition to complex mutations treated with osimertinib have a poor clinical outcome: A real-world data analysis.

The present study aimed to investigate the clinical characteristics and outcomes of patients with advanced non-small cell lung cancer (NSCLC) treated with osimertinib, and focused on the resistance mechanism to osimertinib in a real-world setting. Data from 128 patients with advanced NSCLC who were treated with osimertinib between March 2015 and November 2018 at the Chinese People's Liberation Army General Hospital (Beijing, China) were retrospectively collected, and the associations between mutation types and survival were analysed. In patients treated with osimertinib, the objective response rate reached 60.9% (78/128) and the disease control rate reached 81.3% (104/128), with a median progression-free survival (PFS) time of 12.2 months. A number of complex mutations were identified in the re-analysis after the development of osimertinib resistance, including TP53, KRAS and PIK3CA mutations, epidermal growth factor receptor (EGFR) and MYC amplifications, and mutations associated with SCLC transformation, demonstrating that these mutations may account for osimertinib resistance. The median PFS time for patients with the EGFR T790M mutation (n=41) was significantly longer than that for patients with the T790M mutation and the aforementioned complex mutations (n=13) (16.7 vs. 10.8 months; P=0.001). Patients with a single EGFR mutation (n=87) had a longer median PFS time than those with an EGFR mutation and complex mutations (n=24) (14.63 vs. 6.63 months; P<0.0001). In conclusion, the present study analysed the effects of osimertinib in patients with advanced NSCLC with EGFR mutations, particularly T790M mutations. The results indicated that the efficacy of osimertinib was weakened when patients had complex mutations, suggesting that complex mutations may be responsible for resistance to osimertinib.