Liver-directed moderately hypo-fractionated radiotherapy combined with pembrolizumab and bevacizumab for advanced hepatocellular carcinoma: a retrospective observational study of 23 cases.

Background: Programmed cell death protein 1 (PD-1) or its ligand (PD-L1) monoclonal antibody combined with bevacizumab (a monoclonal antibody targeting vascular endothelial growth factor) has been established as first-line systemic treatment for advanced hepatocellular carcinoma (HCC). Radiotherapy is a crucial local treatment for HCC. Mutual efficacy enhancement has been reported between radiotherapy, anti-angiogenesis therapy and immunotherapy in preclinical researches, but not been validated in clinical practice. Whether radiotherapy can enhance efficacy of anti-PD-1 immunotherapy plus bevacizumab for HCC remains unclear. This retrospective observational study aimed to appraise efficacy and safety of the combination of radiotherapy with pembrolizumab (a PD-1 monoclonal antibody) and bevacizumab for advanced HCC for the first time.

Methods: Patients with advanced HCC treated by intrahepatic tumor-directed moderately hypo-fractionated radiotherapy combined with pembrolizumab and bevacizumab were consecutively included. Clinicopathological characteristics, therapeutic outcomes and treatment-related adverse events (TRAEs) were recorded and evaluated.

Results: A total of 23 patients were eventually enrolled. Median cycles of pembrolizumab and bevacizumab were 4 (median, 1-8) and 4 (median, 1-9) cycles. The objective response rates and disease control rates of irradiated intrahepatic HCC and non-irradiated extrahepatic HCC were 34.8% [95% confidence interval (CI), 16.4-57.3%] 10.0% (95% CI, 1.2-31.7%), and 91.3% (95% CI, 72.0-98.9%) 70.0% (95% CI, 45.7-88.1%), respectively. The median progression-free survival (PFS) and overall survival (OS) were 6.6 (95% CI, 4.7-8.5) and 18.3 (95% CI, 8.2-33.6) months, and 12-month PFS and OS rates were 17.5% (95% CI, 7.0-28.0%) and 60.9% (95% CI, 50.7-71.1%). Two patients (8.7%) with locally advanced, unresectable HCC eventually underwent curative resection of tumors after this trimodal treatment. Eighteen patients (78.3%) had ≥ grade 3 TRAEs, with myelosuppression and transaminase increase as the most common.

Conclusions: This study firstly reported that combining radiotherapy with pembrolizumab and bevacizumab was preliminarily a feasible and effective therapeutic choice for advanced HCC in despite of more TRAEs. This tri-modal regimen may be a potential conversion therapy for unresectable, locally advanced HCC. The limitations of this study are its retrospective nature and small sample size; therefore, big-sample prospective studies are warranted to further investigate this tri-modal regimen.