Stereotactic body radiotherapy with sintilimab and bevacizumab biosimilar in anti-PD-1 refractory hepatocellular carcinoma: the ReUNION-1 phase 2 trial

Immune checkpoint inhibitor (ICI) resistance in hepatocellular carcinoma (HCC) poses a major therapeutic challenge. Here we present a Phase 2 trial evaluating stereotactic body radiotherapy (SBRT) combined with sintilimab and bevacizumab biosimilar (PD-1/VEGF blockade) to overcome resistance in ICI-refractory HCC. Twenty-one patients with progressive HCC after ICI therapy receive SBRT followed by sintilimab 200 mg and bevacizumab biosimilar 15 mg/kg every 3 weeks. The primary outcome, objective response rate in non-irradiated lesions is 33.3%, with a disease control rate of 66.7%. Median progression-free survival is 6.2 months, and estimated median overall survival is 24.4 months. SBRT achieves 100% local control, with 33.3% experiencing grade 3 or higher adverse events. Proteomic profiling reveals that responders exhibit lower baseline IFN-γ and elevated IL-6, while post-SBRT increases in IFN-γ, IL-2, and IL-6 correlate with improved outcomes. These results indicate that combination of SBRT in ICI-refractory HCC is effective, well-tolerated, and may be guided by cytokine assessment.