Clinical significance of soluble programmed cell death ligand-1 (sPD-L1) in hepatocellular carcinoma patients treated with radiotherapy

Purpose: To investigate the clinical implications of the soluble programmed cell death-ligand 1 (sPD-L1) level in hepatocellular carcinoma (HCC) patients treated with radiotherapy (RT). Materials/methods: HCC patients treated with RT between June 2011 and March 2015 were prospectively recruited and sPD-L1 levels were measured using an enzyme-linked immunosorbent assay. Blood samples were obtained at the RT start, RT end, and 1-month follow-up. The associations of the sPD-L1 level with the clinical features and outcomes were analyzed. Results: Fifty-three patients with HCC were included. Thirty-four patients received conventional fractionated RT with hepatic arterial infusional chemotherapy, while 19 patients received stereotactic body radiotherapy (SBRT). The initial sPD-L1 level was significantly associated with stage, tumor size, portal vein tumor thrombosis, and venous invasion. The overall-survival was significantly poorer in patients with a higher level of initial sPD-L1 (≥1.315 pg/mL). A higher level of sPD-L1 at 1 month (≥12.9 pg/mL) was significantly related to early lung metastasis. The sPD-L1 level was significantly increased after RT and the change pattern of sPD-L1 was different between two RT schemes. Conclusions: The level of sPD-L1 was associated with tumor aggressiveness and outcomes, suggesting its role as a possible predictive biomarker. The increases in sPD-L1 after RT suggests that combined treatment with RT and immune checkpoint inhibitors may be a promising therapeutic strategy in HCC.