2200 - Effect of Radiotherapy on Immunotherapy Efficacy for Advanced EGFR Mutant Non-Small Cell Lung Cancers after Osimertinib Resistance

Y. Zhou¹, Z. Li², and J. Li³; ¹Shandong Cancer Hospital and Institute,Shandong First Medical University and Shandong Academy of Medical Sciences,, Jinan, China, ²SHANDONG CANCER HOSPITAL AND INSTITUTE, JINAN, China, ³Department of Thoracic Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China

Purpose/Objective(s): Radiotherapy (RT) combined with immunotherapy has the potential synergistic treatment effect for lung cancers. However, supportive correlative clinical data are limited for this combination in the Epidermal growth factor receptor (EGFR)-mutant population. In this study, we aimed to demonstrate the addition of RT in the course of immunotherapy have effect on prognosis in EGFR mutant non-small cell lung cancers after osimertinib resistance. Materials/

Methods: A total of 90 patients with advanced non-small cell lung cancer with EGFR mutations who had acquired resistance to osimertinib were included. Patients were divided into two groups: ICIs + RT group (40.0%) and ICIs + non- RT group (60.0%). The Kaplan-Meier method was used for survival analysis. Univariate and multivariate analyses were performed to identify the factors affecting the effectiveness of ICIs in these patients.
Results: 36 patients received local radiotherapy, including 17 receiving brain radiotherapy, 11 receiving bone radiotherapy, 5 receiving lung radiotherapy, and 3 receiving liver radiotherapy. At the end of the last follow-up period, the median progression-free survival (PFS) and overall survival (OS) for all patients were 4.8 months and 15.1months. There was no significant difference in baseline clinical characteristics between the two groups (P>0.05). The addition of RT significantly increased the median PFS from 2.8 to 6.3 months (P = 0.001) and OS from 12.5 to 30.7 months (P=0.0057) compared to non-combination therapy. Univariate and multivariate analyses showed that ICIs plus RT was an independent predictive factor for PFS improvement (P=0.001; HR,0.432; 95% CI, 0.257–0.726). ICIs plus RT (P=0.007, HR,0.365, 95% CI, 0.175–0.762) and Karnofsky Performance Status (KPS) (P=0.042; HR,0.372; 95% CI, 0.143–0.966) were independent prognostic factors for overall survival.
Conclusion: In osimertinib-resistant patients with EGFR mutant NSCLCs, combination of immunotherapy with radiotherapy can significantly delay the tumor progression and prolonged OS compared with patients who did not receive radiotherapy.