Immunotherapy with and without radiotherapy following the diagnosis of bone metastasis for stage 4 non-small cell carcinoma.

e20574 Background: This retrospective study compared the effect of immunotherapy (IT) on survival in patients with stage 4 non-small cell lung carcinoma (NSCLC) who did or did not receive radiotherapy (RT) after a diagnosis of bone metastasis. Methods: The TriNetX database (2013-2023) was queried for adults (≥18 years) receiving IT for stage 4 NSCLC with squamous cell, adenocarcinoma, and NSCC histologies. Patients were stratified based on RT following bone metastasis, and propensity-matched to balance baseline characteristics. Analyses included descriptive analysis, measures of association, Kaplan-Meier survival analysis, and Cox proportional hazards modeling. Results: Among 1,778 matched patients, 889 patients received RT after bone metastasis and 889 did not. RT+IT was associated with higher 30- and 90-day survival ( p < 0.0001 and p = 0.0497, respectively) compared to IT alone. Log-rank tests showed higher hazard ratios (HR) for IT alone at 30-days (HR = 1.889, p < 0.0001), 90-days (HR = 1.284, p = 0.0071), and 1-year (HR = 1.172, p = 0.0152). Stratified analyses by adenocarcinoma or squamous cell histology demonstrated improved 30-day survival in both groups. A Cox proportional hazards model revealed a HR of 1.264 for the IT-only cohort ( p = 0.0001). Higher hazards were noted for metastasis of the adrenal gland (HR = 1.325), liver/bile duct (HR = 1.178), lymph nodes (HR = 1.125), nivolumab (HR = 1.286), and zoledronic acid (HR = 1.223), suggesting these diagnoses and treatments are more effective with RT. Conclusions: RT improved survival for stage 4 NSCLC patients receiving IT. Lung cancer remains the second most common cancer and the leading cause of death in the United States. This study highlights the potential importance of combining RT with IT in improving survival outcomes, especially in patients with more advanced diseases.