PDCD1 and hepatocellular carcinoma: In a small cohort of 10 patients with advanced HCC treated with PD-1 inhibitors, the presence of PD-L1-expressing CTCs (PD-L1+ CTCs) correlated with treatment response: five out of six patients with PD-L1+ CTCs achieved disease control, contrasting with no response among the four patients lacking PD-L1 expression [82].