Eligible patients were between 18 and 75 years of age with histologically proven T1 or T2 HCC (according to the AJCC TNM Classification of HCC, 7th); an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1; Child-Pugh class A or B; no history of neoadjuvant therapy; no lymph node or distant metastasis; no intrahepatic or extrahepatic recurrence at radiological follow-up (4-6 weeks after surgery); adequate bone marrow, hepatic, and renal function according to laboratory test results. Patients were excluded if they had undergone margin-positive resections or resection of recurrence HCC; had lymph node or distal metastases; underwent concomitant ablation or radiation during surgery; were subjected to severe postoperative complications; had serious co-morbidities; had known allergy to iodine and drugs used in TACE; or if an investigator judged participation to be incompatible with the safety of the study. This clinical trial was done in accordance with the Declaration of Helsinki and local laws. All participants provided written informed consent. The study protocol was approved by the institutional Medical Ethics Review Committee.

Participants enrolled in the adjuvant TACE group received one to two cycles of TACE with an interval of 4\~6 weeks, and the first TACE was given within 1 week after randomization. Participants enrolled in the observation group were subjected to active surveillance without any adjuvant treatment. The TACE procedure was performed as follows. Briefly, a 4F or 5F catheter was introduced into the abdominal aorta through the superficial femoral artery according to the Seldinger technique. Angiography of the celiac and superior mesenteric arteries was performed to show the hepatic arterial supply. Then the left and right hepatic arteries were accessed by a microcatheter and intraarterial epirubicin (40 mg) and oxaliplatin (150 mg) in a mixture of lipiodol (3～5 mL) were injected. The follow-up interval was 3 months in the first two years postoperatively and 6 months thereafter. During each follow-up visit, blood tests including complete blood count, serum level of alpha-fetoprotein (AFP), and liver function tests were examined. During follow-up, contrast-enhanced abdominal CT or MRI scans were first performed at 3 months after operation and then every 6 months, with liver ultrasonography performed 3 months after every CT/MRI scan thereafter. Chest CT was performed at 1-year intervals. All participants with tumor recurrence were treated according to the decision made by a multidisciplinary board.

The primary endpoint was RFS, defined as the time from randomization to the first documented HCC recurrence by independent radiological assessment or death due to any cause, whichever occurred first. Secondary endpoints were OS (defined as the time from randomization to death due to any cause), RFS rate, and safety. Patients who were recurrence-free or alive at the point of final analysis were censored at the date of the last follow-up.

Intrahepatic recurrence was defined according to the non-invasive criteria of the European Association for the Study of the Liver (EASL) guideline. Newly-onset intrahepatic nodules with the longest diameter ≥ 1cm and a typical hallmark of HCC on contrast-enhanced CT/MRI imaging (hypervascular in the arterial phase with washout in the portal venous or delayed phase) were diagnosed as HCC recurrence. Lesions ≥ 1cm without a typical vascular pattern could also be diagnosed as HCC recurrence by evidence of a fast growth pattern as showed in subsequent scans and were independently reviewed by two radiologists. Extrahepatic recurrence was defined as per Response Evaluation Criteria in Solid Tumors. The safety of adjuvant TACE was assessed according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.03.