2199 - First-Line Tyrosine Kinase Inhibitor with or without Upfront Stereotactic Body Radiotherapy for Residual Primary Lesions in Advanced EGFR-Mutated Non-Small Cell Lung Cancer

W. Zhou¹, D. Tao¹, Z. Yuan¹, D. Yang², Y. Jiang¹, E. Munai³, S. Zeng¹, and Y. Wu⁴; ¹Department of Radiation Oncology, Chongqing University Cancer Hospital, Chongqing, China, ²Department of Radiation Oncology, Chongqing University Cancer Hospital, Chongqing, China., Chongqing, China, ³School of Medicine, Chongqing University, Chongqing, China, Chongqing, China, ⁴College of Medicine, Chongqing University, Chongqing, China

Purpose/Objective(s): The effectiveness of upfront stereotactic body radiotherapy (SBRT) for residual primary lesions in advanced NSCLC patients treated with first-line EGFR-TKI is still unclear. This study aimed to evaluate the efficacy and safety of combining EGFR-TKI therapy with SBRT to residual primary lesions in EGFR-mutant NSCLC patients. Materials/

Methods: Patients with advanced NSCLC treated with first-line EGFR-TKIs with or without SBRT for the residual primary lung tumors were identified. All eligible patients were divided into two groups: EGFR-TKI alone group and EGFR-TKI plus SBRT group. The SBRT was delivered to the primary residual lung lesion when the patients achieved stable disease within two sequential treatment evaluations. The primary endpoint was progression-free survival (PFS). Overall survival (OS) and adverse effects (AEs) were secondary endpoints. A two-sided P value of 0.05 was considered statistically significant. All of the statistical analyses were performed with statistical software.
Results: A total of 485 patients with advanced NSCLC were screened, and 58 patients were eligible for enrollment in this study. Of the 58 eligible patients, 43 received EGFR-TKI treatment alone and 15 patients received EGFR-TKI treatment plus SBRT to lung primary tumor. The TKIs plus SBRT group exhibited a significant extension in PFS compared to the TKIs alone group (mPFS: not reached vs. 10.2 months, P < 0.001). Multivariate Cox regression analysis revealed that SBRT was an independent favorable factor for PFS (HR = 0.16, 95% CI 0.05–0.53, P = 0.003). The patients in the TKIs plus SBRT group demonstrated a significantly longer OS than those in the TKIs alone group (mOS: not reached vs. 40.5 months, P = 0.027). However, the multivariate Cox regression analysis for OS showed that TKIs plus SBRT was not an independent prognostic factor (P = 0.953). No significant difference in the incidence of AEs of any grade was observed between the two groups (46.7% vs 27.9%, P = 0.213). No Grade 4 or 5 AEs was reported in both groups.
Conclusion: Upfront SBRT for residual primary lesions could significantly improve PFS in advanced EGFR-mutated NSCLC patients treated with first-line EGFR-TKIs compared with TKIs alone. This finding suggests that upfront SBRT for residual primary lesions is a new potentially effective and tolerable treatment option for this subgroup of patients.