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Down-staging Outcomes for Hepatocellular Carcinoma: Results from the Multicenter Evaluation of Reduction in Tumor Size before Liver Transplantation (MERITS-LT) Consortium.

BACKGROUND/AIMS
United Network of Organ Sharing (UNOS) has adopted uniform criteria for down-staging (UNOS-DS) of hepatocellular carcinoma (HCC) prior to liver transplantation (LT), but down-staging success rate and intention-to-treat outcomes across broad geographic regions are unknown.


METHODS
In this first multi-regional study (7 centers, 4 UNOS regions), consecutive patients with HCC undergoing down-staging based on UNOS-DS criteria were prospectively evaluated from 2016-2019 (n=209).


RESULTS
Probability of successful down-staging to Milan criteria and dropout at 2 years from initial down-staging procedure was 87.7% and 37.3%, respectively. Pre-treatment AFP-L3 >10% (HR 3.7, p=0.02) was associated with increased dropout risk. When comparing chemoembolization (n=132) and Y-90 radioembolization (n=62) as initial down-staging treatment, there were no differences in mRECIST response, probability of or time to successful down-staging, waitlist dropout or LT. Probability of LT at 3 years was 46.6% after a median of 17.2 months. In the explant, 17.5% had vascular invasion and 42.8% exceeded Milan criteria (under-staging). The only factor associated with under-staging was the sum of the number of lesions plus largest tumor diameter on last pre-LT imaging, and odds of under-staging increased by 35% per 1 unit increase in this sum. Post-LT survival at 2 years was 95% and HCC recurrence occurred in 7.9%.


CONCLUSION
In this first prospective multi-regional study based on UNOS-DS criteria, we observed successful down-staging rate of >80%, and similar efficacy of chemoembolization and Y-90 radioembolization as initial down-staging treatment. A high rate of tumor under-staging was observed despite excellent 2-year post-LT survival of 95%. Additional LRT to reduce viable tumor burden may reduce tumor under-staging.