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 = .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 = .042). Patients with disease progression were more likely to exhibit monocytes with increased PD-L1 positivity after 28 (p = .020) or 42 (p = .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.