2152 - Upfront Stereotactic Body Radiotherapy to the Residual Primary Lung Lesions after First-Line Systemic Therapy in Polymetastatic Non-Small Cell Lung Cancer

D. Tao, Z. Yuan, L. Sun, L. L. WANG, L. Du, D. Yang, Y. Jiang, W. Zhou, Y. Wang, and Y. Z. Wu; Department of Radiation Oncology, Chongqing University Cancer Hospital, Chongqing, China

Purpose/Objective(s): Stereotactic body radiotherapy (SBRT) significantly improved the survival of oligometastatic (=5 lesions) non-small cell lung cancer (NSCLC). However, the role of SBRT in NSCLC patients with more than five metastases is still unclear. This study aimed to investigate the efficacy and safety of upfront SBRT to the residual primary lung lesions for polymetastatic (>5 lesions) NSCLC treated with first-line systemic therapy. Materials/

Methods: The NSCLC patients with more than five metastases received first-line systemic therapy with or without upfront SBRT to the residual primary lung lesions were screened retrospectively. The SBRT was delivered at the time of maximal response to systemic therapy. The progression-free survival (PFS) was defined as the time interval from the start of first-line systemic therapy to disease progression or death from any cause. Overall survival (OS) was defined as the time interval from the start of first-line systemic therapy to death. The primary endpoint was PFS and the second endpoints were the OS and adverse effects (AEs). A two-sided P value of 0.05 was considered statistically significant. All of the statistical analyses were performed with statistical software.
Results: Six hundred and seventy-three patients were screened. A total of 33 patients were eligible and included in the analysis of this study. The median age of the entire cohort was 64 years (range, 37–94 years). Twenty-one (63.6%) patients were male and 19 (57.6%) patients were smokers. Twenty-two patients were treated with target therapy and 11 patients were treated with the combination of chemotherapy and immunotherapy. Among all enrolled patients, 15 (45.5%) patients received first-line systemic therapy with upfront SBRT to the residual primary lung lesions (systemic therapy plus SBRT group) and 18 (54.5%) patients received first-line systemic therapy alone (systemic therapy alone group). The patients in the systemic therapy plus SBRT group demonstrated significantly longer PFS than those in the systemic therapy alone group (mPFS: 27.0 months vs. 10.2 months, P = 0.002). Cox regression multivariate analysis revealed that systemic therapy plus SBRT was an independent favorable factor for PFS (HR = 0.287, 95%CI: 0.118-0.696, P = 0.006). The systemic therapy plus SBRT group showed a trend toward a favorable OS compared to the systemic therapy alone group (mOS: 57.3 months vs 32.5 months, P = 0.425). There was no statistically significant difference in AEs between the two groups.
Conclusion: Upfront SBRT to the residual primary lung lesions after first-line systemic therapy significantly improved the PFS of NSCLC patients with polymetastatic disease. These findings suggest that first-line systemic therapy plus SBRT might be a promising novel treatment option for this subgroup of patients.