Abstract
BACKGROUND & AIMS: The combination of locoregional therapies (LRT) with immune checkpoint inhibitors (ICIs) in unresectable hepatocellular carcinoma (HCC) is expected to enhance immune-mediated anti-tumor effects. Although clinical trials are underway, an unmet need exists to understand the immunological effects of LRT and how they evolve. This study aimed to longitudinally assess immune cell subpopulations and checkpoint expression after LRT. METHODS: This prospective, single-center study (DRKS00026994) enrolled 128 consecutive patients with unresectable HCC, who underwent conventional transarterial chemoembolization (cTACE), interstitial high-dose-rate brachytherapy (iBT), or a combination of cTACE and iBT (from July 2020 to September 2021). Peripheral blood samples were collected at baseline, 1 day after LRT, and 2 months after LRT. Immune cells were quantified using spectral flow cytometry. Immune cell subpopulations and checkpoint molecule expression were compared longitudinally and among treatment groups. Cluster analyses were used to explore immune profiles and their relationship with treatment response. RESULTS: Changes in absolute immune cell counts were detected 1 day after LRT, which largely diminished by 2 months. Myeloid populations increased significantly, whereas most lymphoid cells decreased after LRT. However, relative proportions of anti-tumoral CD56(diminished) NK cells (Cohen's D = 0.40, 95% CI 0.19-0.61, p <0.01), CD8(+) T cells (Cohen's D = 0.15, 95% CI -0.06 to 0.35, p = 0.01), and CTLA-4 expression on T cells (CD4(+): Cohen's D = 0.54, 95% CI 0.33-0.75, p <0.01; CD8(+): Cohen's D = 0.15, 95% CI 0.36-0.78, p <0.01) were upregulated at 1 day, particularly after cTACE. Cluster analysis distinguished responders from non-responders based on distinct immune profiles. CONCLUSIONS: LRT induce an early pro-inflammatory immune response with increased myeloid, CTLA-4(+) T cells, and cytotoxic lymphocytes, particularly after cTACE. These findings support the potential of immune profiling to guide personalized combination strategies with LRT and systemic immunotherapies. IMPACT AND IMPLICATIONS: Combining locoregional therapies (LRT) with immune checkpoint inhibitors (ICI) in unresectable hepatocellular carcinoma (HCC) aims to enhance immune-mediated anti-tumor effects. However, potential immunological targets remain unknown. Immune profiling could be facilitated as a tool to predict tumor response to LRT and may inform personalized treatment planning, selecting patients who may benefit from an additional ICI therapy. The study's design may guide future investigations to identify the temporal dynamics of immune cell alterations following LRT to identify the appropriate time point to co-administer the ICI application. CLINICAL TRIAL NUMBER: DRKS00026994 (https://drks.de/search/de/trial/DRKS00026994).