Background Embolization of collateral arteries is important for transcatheter hepatic arterial chemoembolization (TACE)in patients with hepatocellular carcinoma (HCC). We evaluated the efficacy and safety of TACE, and the prevention and management of complications among patients in whom the intal thoracic artery (ITA) was involved.Methods A total of 3614 cases of HCC were treated with 12 645 TACEs and 211 of these cases were given ITA angiography, including 156 cases of which the ITA was involved. We performed 562 TACEs in the 156 cases. We analyzed imaging examinations, types of embolization, and the incidence, prevention, and treatment of complications.Results The ITA was successfully embolized in 156 cases. Angiography of the ITA showed that the major trunks were thickened with an increased number of branching vessels, contributing to intrahepatic and extrahepatic tumor blood supply. Different embolization methods were selected according to the blood supply, to effectively embolize the tumor and mitigate or avoid serious complications. TACE with ITA embolization extended the mean interval time between two treatments from 2.54 months (1-17 months) to 4.23 months (1-30 months) compared with that without ITA embolization.The ITA supplied the HCC in the following instances: HCC was located in the ventral hepatic area and abutted the diaphragm (P=0.0064) and repeated TACE (P=0.0003). The survival rate of TACE with ITA embolization for HCC was better than TACE without ITA embolization (P ＜0.00001 ).Conclusions In cases with massive HCC or nodular HCC, the ITA may be involved in supplying blood to the tumor.This occurs when the tumor is positioned in the ventral hepatic area and abuts the diaphragm (S2, S4, and S8), and especially if cases have a previous history of TACE. In this case series, embolization was effective, extended the mean interval time of interventional therapy, and prolonged survival time.