BACKGROUND:The efficacy and safety of transarterial chemoembolization (TACE) plus lenvatinib in patients with hepatocellular carcinoma (HCC) and portal vein tumor thrombus (PVTT) have not been evaluated. METHODS: In this open-label, single-center, randomized trial (ClinicalTrials.gov identifier: NCT04127396), participants with previously untreated HCC and type I-IV PVTT were randomized 1:1 to receive TACE plus lenvatinib (arm L; orally once daily, 12 mg for body weight ≥60 kg or 8 mg for body weight <60 kg) or TACE plus sorafenib (arm S; 400 mg orally twice daily in 28-day cycles). The primary end point was time-to-progression (TTP; time from randomization to disease progression) and secondary end points included objective response rate and toxicity. Prognostic factors were evaluated using a multivariable Cox proportional hazards model. RESULTS: Between December 30, 2018 and May 31, 2020, 64 patients were randomized (arm L, n = 32; arm S, n = 32); most patients had type I/II PVTT (71.9%), and the median target tumor diameter was 9.8 cm (range, 3.8-21.8). After a median follow-up of 16.1 months, patients in arm L had a higher median TTP (4.7 vs 3.1 months; hazard ratio [HR], 0.55; 95% CI, 0.32-0.95; P = .029) and objective response rate (53.1% vs 25.0%, P = .039) versus arm S. Multivariable analysis showed that TACE plus lenvatinib was significantly associated with higher TTP versus TACE plus sorafenib (HR, 0.50; 95% CI, 0.28-0.90; P = .021). Comparable safety profiles were observed in arms L and S. CONCLUSIONS: TACE plus lenvatinib was safe, well tolerated, and had favorable efficacy versus TACE plus sorafenib in patients with advanced HCC with PVTT and large tumor burden. Cancer 2021;127:3782-3793.