Switching to systemic therapy after locoregional treatment failure: Definition and best timing

In patients with unresectable hepatocellular carcinoma (HCC) without both macrovascular invasion and extrahepatic metastasis, the initial treatment choice recommended is transarterial chemoembolization (TACE). Before sorafenib came into wide use, TACE had been pointlessly carried out repeatedly. It was in the early 2010s that the concept of TACE refractory was advocated. Two retrospective studies from Japan indicated that conversion from TACE to sorafenib the day after patients were deemed as TACE refractory improved overall survival compared with continued TACE, according to the definition by the Japan Society of Hepatology. Nowadays, phase 3 trials have shown clinical benefits of several novel molecular target agents. Compared with the era of sorafenib, sequential treatments with these molecular target agents have gradually prolonged patients' survival and have become major strategies in patients with HCC. Taking these together, conversion from TACE to systemic therapies at the time of TACE refractory, compared with before, may have a greater impact on survival and may be considered deeper in the decisions-making process in patients with unresectable HCC who are candidate for TACE. Up-to-date information on the concept of TACE refractory is summarized in this review. We believe that the survival of patients with unresectable HCC without both macrovascular invasion and extrahepatic metastasis may be dramatically improved by optimal timing of TACE refractory and switching to systemic therapies.