Investigation of the efficacy of the combination of stereotactic body radiation therapy and immunotherapy in patients with metastatic solid tumors

Purpose: to study the combination of immunotherapy and stereotactic body radiation therapy (SBRT) in patients with metastatic solid tumors. Material and Methods. The efficacy of a combination of SBRT and systemic therapy with immune checkpoint inhibitors was assessed in 20 patients with metastatic solid tumors resistant to systemic therapy. SBRT was administered in 3 fractions of 8 Gy. Progression-free survival (PFS), overall survival (OS), and local control were assessed from the end of irradiation. The objective response rate was determined 12 weeks after completion of STRT using iRECIST criteria. Statistical analysis was performed using Microsoft Excel 2010 and R v. 3.6.2. Survival analysis was performed using the Kaplan-Mayer method. Results. The objective response rate at 12 weeks after SBRT was 15 %. The 3and 6-month local control rates were 75 and 44.4 %, respectively. The median PFS reached 4 months, and the 1-year OS rate was 60.5 %. Conclusion. Progressionfree survival rates obtained in our study suggest that the combination of SBRT and immune checkpoint inhibitors may provide a treatment response even in patients with extremely unfavorable prognosis.