Sintilimab plus bevacizumab as maintenance therapy for patients with unresectable hepatocellular carcinoma treated with transarterial chemoembolization: A phase Ib study

e16165 Background: Sintilimab (a PD-1 inhibitor) plus bevacizumab (Sin-Bev) has been demonstrated to confer a significant survival benefit over sorafenib in patients with unresectable hepatocellular carcinoma (uHCC). This phase Ib study (NCT04592029) aimed to evaluate the safety and efficacy of Sin-Bev for patients with uHCC who received transarterial chemoembolization (TACE). Methods: The key eligibility criteria were: age ≥ 18 years; BCLC B/C stage uHCC; no prior systemic therapy and non-curative local treatments; Child-Pugh score ≤7; ECOG PS ≤1. This study included dose escalation and dose expansion stages. In the dose escalation stage, a 3+3 design was employed to determine the safety of a standard dose of sintilimab (200 mg Q3W) plus two possible doses of bevacizumab (group A: 7.5 mg/kg Q3W; group B: 15.0 mg/kg Q3W) after TACE. In the dose expansion stage, additional 30 patients were randomized 1:1 to each group. Sintilimab and bevacizumab was started at 3-7 days after the first TACE (TACE was repeated on demand). The primary endpoints were the incidence of adverse events (AEs) and progression free survival (PFS). The secondary endpoints included objective response rate (ORR), disease control rate (DCR) and overall survival (OS). Results: At the time of data cutoff (January 20th, 2022), 36 patients were enrolled (18 in each group). One patient in group A withdrew from the study after the first cycle of treatment. Of the remaining 35 patients, 20 (57.1%) had disease at BCLC C stage, 15 (42.9%) had macroscopic vascular invasion and 11 (31.4%) had extrahepatic metastasis. The mean largest tumor size was 10.5±5.2 cm. The median follow-up was 9.57 (range, 4.4-15.6) months. Thirty-one patients (86.1%, n=36) had treatment-related AEs (83.3% in group A vs. 88.9% in group B, P=1.000). All the AEs were mild (