Potential of circulating immune cells as biomarkers of nivolumab treatment efficacy for advanced hepatocellular carcinoma

Background: Remarkable progress has been made in immunotherapy, specifically antibodies for programmed death 1 (PD-1) or programmed death-ligand 1 (PD-L1), for treating advanced cancers. In this study, we explored whether circulating immune cells can be used as biomarkers of the efficacy of such therapy. Methods: We enrolled patients who received nivolumab, an anti-PD-1 antibody, for advanced hepatocellular carcinoma (HCC) in clinical trials and who consented to the collection of their peripheral blood. Using flow cytometry, we analyzed lymphocyte subclasses and the PD-1 or PD-L1 positivity of immune cells. These results were compared between patients with disease control (complete response, partial response, or stable disease) and those with disease progression. Results: This study included 16 patients. The objective response rate was 19%, and the disease control rate was 75%. The hemogram results and the percentage of total αβ T cells or CD4 T cells did not significantly change after nivolumab treatment; moreover, they were not associated with treatment outcomes. The number of CD8 T cells significantly increased after 4 weeks (p=0.016); however, this change was not associated with treatment outcomes. Patients with disease control exhibited peripheral B cells with significantly lower pretreatment PD-1 positivity than did patients with disease progression (p=0.042). Patients with disease progression were more likely to exhibit monocytes with increased PD-L1 positivity after 28 (p=0.020) or 42 (p=0.008) days of treatment. Conclusion: The low pretreatment PD-1 positivity of peripheral B cells and the constant posttreatment PD-L1 positivity of monocytes were associated with disease control after nivolumab treatment for advanced HCC.