Lineage-specific regulation of PD-1 expression in early-stage hepatocellular carcinoma following 90yttrium transarterial radioembolization - Implications in treatment outcomes.

BACKGROUND

Hepatocellular carcinoma (HCC) remains one of the leading causes of cancer-related deaths in the world. Liver-directed therapies, including 90Yttrium (90Y) radioembolization, play an integral role in the management of HCC with excellent response rates. This has led to clinical trials of immunotherapy in combination with 90Y. Elevated PD-1 expression and lymphopenia were recently shown as risk factors for disease progression in early-stage HCC treated with liver-directed therapies. The aim of this study was to investigate PD-1 expression dynamics in bridge/downstage to transplant in HCC patients receiving first-cycle 90Y and evaluate the impact of these changes on response rates and time-to-progression (TTP).

METHODS

Patients with HCC receiving first-cycle 90Y as a bridge to liver transplantation (n = 99) were prospectively enrolled. Blood specimens were collected before 90Y and again during routine imagining follow-up to analyze PD-1 expression via flow cytometry. Complete and objective response rates (CR and ORR) were determined using mRECIST.

RESULTS

In 84/88 patients with available follow-up imaging, 83% had a localized ORR with 63% having localized CR. For overall response, 71% and 54% experienced ORR and CR, respectively. Post-90Y PD-1 upregulation in CD8 + associated with HCC progression and decreased TTP. Treatment with 90Y was associated with an anticipated significant post-treatment drop in lymphocytes (P < 0.001) that was independent of PD-1 expression for either CD4+ or CD8+ T cells (P = 0.751 and P = 0.375) and not associated with TTP risk. The change in lymphocytes was not correlated with PD-1 expression following treatment nor TTP.

CONCLUSIONS

Elevated PD-1 expression on peripheral T cells is associated with increased risk of HCC progression and shorter time to progression in bridging/downstaging to transplant HCC patients undergoing first-cycle 90Y. Treatment-induced lymphopenia was not associated with treatment response, or increased progression risk, suggesting this anticipated adverse event does not impact short-term HCC outcomes.