BACKGROUND/OBJECTIVES: The real-world survival of patients with unresectable hepatocellular carcinoma (uHCC) treated with lenvatinib has been explored retrospectively with a small sample size. We conducted a prospective observational 2-year extension study (510 study) of a 1-year observational post-marketing study of lenvatinib (504 study) to evaluate the long-term overall survival (OS) of patients with uHCC treated with lenvatinib and associated factors with a large sample size. METHODS: Patients with uHCC included (July 2018 to January 2019) in the 504 study and who consented were eligible for the 510 study and were followed for up to 3 years after lenvatinib treatment initiation. Using the data from the 504 study and 510 study of the 504 study analysis set, we estimated the OS, the time from the first lenvatinib dose to all-cause death by the Kaplan-Meier method (ClinicalTrials.Gov Registration ID, 504 study: NCT03663114
510 study: NCT04008082). RESULTS: The 703 patients included in the analysis were followed for a median period (min, max) of 12.5 months (0.1, 44.8). The median OS (95% confidence interval) was 16.6 months (15.4, 18.5). OS was significantly ( CONCLUSIONS: This large-scale, prospective, real-world study demonstrated a long OS, comparable to that reported in the global Phase III REFLECT trial. More advanced-stage tumors and worse hepatic function have been suggested as OS-associated factors, consistent with previous reports.