Real-World Data for Integration Strategy of Radiotherapy (RT) With Immunotherapy in Metastatic Non-Small Cell Lung Cancer (NSCLC)

Abstract

<h3>Purpose/Objective(s)</h3> Immune checkpoint inhibitors (ICIs) have proven effective in metastatic NSCLC. RT has been used for symptom palliation or aggressive consolidation with improvement of survival in this group of patients. The question of when and how to combine RT with ICIs needs to be further defined in this combination therapeutic strategy in NSCLC. The growing body of evidence demonstrated that RT-ICIs sequence, dose of RT and location of RT are matter to the treatment outcome. We retrospectively analyzed our institutional data as real-world data to further illustrate the role of RT in combination with ICIs for metastatic NSCLC. <h3>Materials/Methods</h3> We retrospectively studied patients from a single institution diagnosed with metastatic NSCLC who were treated with RT-ICIs. The impact of overall survival (OS) from patients' characteristic, histology of tumor, PD-L1 expression, RT BED₁₀ (biological equivalent dose) dose, number of site of RT, RT to bone/no-bone metastasis site, and sequence of RT-ICIs as well as neutrophil-lymphocyte ratio (NLR) before and after RT were analyzed using Kaplan-Meier methods. Cox proportional hazard regression analysis was performed to identify independent predictors for OS. <h3>Results</h3> A total of 80 patients received ICI+RT were enrolled into the study with a median follow-up of 15 months. Median OS 18.8 was months. Univariable analysis revealed that positive OS predictors (<i>P</i> < 0.05) were lower post-RT NLR, sequential RT-ICIs, higher BED₁₀ dose of RT, one site of RT and RT to no-bone metastasis site. The post-RT NLR, and BED₁₀ dose of RT were independent predictors for OS on multivariable Cox proportional hazard regression analysis. Kaplan-Meier estimates median OS of low/high post-RT NLR, sequential/concurrent RT-ICIs, higher/lower BED₁₀ dose of RT, one/a number of RT sites and RT to no bone/bone metastasis sites were 23.7/11.5 mo., 24.5/16.4 mo., 20.6/16.8 mo. and 21.8/16.6 mo., respectively. The histology of tumor, PD-L1 expression and whether received chemotherapy or not did not significantly impact on OS. <h3>Conclusion</h3> Our real-world data supports that synergistic effective of RT can be achieved in combination with ICIs for metastatic NSCLC when RT was admitted with sequential fashion, ablative dose to one and non-bone metastatic site. Together with significant prognostic value of Post-RT NLR, it has been clearly demonstrated that the integration strategy of RT with ICIs should choose RT which would not compromise existing innate immunity of patients.