BackgroundThough atezolizumab plus bevacizumab (A+B) offer promise for unresectable hepatocellular carcinoma (uHCC) treatment, the response rate remains suboptimal. Our previous studies highlighted the potential of transarterial chemoembolization (TACE) when combined with FOLFOX-based hepatic arterial infusion chemotherapy (HAIC) in HCC treatment. This study aims to evaluate the safety and efficacy of A+B plus TACE-HAIC for high tumor burden uHCC (HTB-uHCC). MethodsThis three-center retrospective study involved 82 HTB-uHCC patients administered with TACE-HAIC followed by A+B. We characterized HTB-uHCC patients as those surpassing the up-to-11 criteria, exhibiting VP 3–4, or presenting extrahepatic metastases. The primary outcomes were the objective response rate (ORR) and progression-free survival (PFS). Secondary outcomes encompassed the incidence of treatment-related adverse events (TRAEs) and overall survival (OS). ResultsEmploying the mRECIST criteria, the ORR was 62.2 %, wherein 18 (22.0 %) patients achieved complete response, 33 (40.2 %) demonstrated partial response, 21 (25.6 %) maintained stable disease, and 10 (12.2 %) exhibited disease progression. Impressively, 11 (13.4 %) patients were converted to resectable HCC and underwent curative hepatectomy. The median PFS was 10.1 months (95 % CI, 8.4 to NA), and the median OS was still pending. At the one-year mark, the OS and PFS rates were 92.8 % (95 % CI, 86.1 to 100.0) and 42.9 % (95 % CI, 31.3 to 58.7), respectively. 79 (96.3 %) experienced TRAEs, and 39 (47.6 %) had grade 3–4 TRAEs, though no treatment-related death was recorded. ConclusionsThe findings underscore the potential of the A+B and TACE-HAIC combined treatment for HTB-uHCC patients, marking it as a viable therapeutic option, given its potent efficacy and tolerable safety profile.