For early-stage hepatocellular carcinoma, i.e. Barcelona Clinical Liver Cancer Stage 0, ablation is the standard treatment with a comparable prognosis and less risk of ablation compared with liver resection. However, ablation is demanding on the surgeon and patients often face early recurrence if ablation is not complete. Therefore, it is necessary to find reasonable adjuvant treatment to consolidate the effect of microwave therapy.

For early-stage hepatocellular carcinoma, i.e. Barcelona Clinical Liver Cancer Stage 0, ablation is the standard treatment with a comparable prognosis and less risk of ablation compared with liver resection. However, ablation is demanding on the surgeon and patients often face early recurrence if ablation is not complete. Therefore, it is necessary to find reasonable adjuvant treatment to consolidate the effect of microwave therapy. There is no consensus on postoperative adjuvant therapy, especially for the management of early-stage HCC. Most scholars believe that HCC in this period does not have high-risk factors for tumor recurrence, thus neglecting the role of adjuvant therapy. Early studies have found that microwave ablation can alter the tumor microenvironment, which is conducive to the action of immune checkpoint inhibitors such as PD-1 inhibitors and even has a synergistic anti-tumor effect. We therefore designed this prospective cohort study to explore the efficacy and safety of adjuvant PD-1 inhibitors after microwave surgery.

Inclusion Criteria:

• Aged 18-75 years
• Pathological type is HCC, BCLC stage 0-A
• No extrahepatic HCC
• No radiographic recurrence at 2-4 weeks after ablation
• Eastern Cooperative Oncology Group (ECOG) performing status of 0-1
• Child-Pugh grade A or B and adequate hematologic and organ function

Exclusion Criteria:

• Any history of other malignant tumors or recurrent HCC
• Any preoperative treatment for HCC including local and systemic therapy
• Any acute active infectious diseases, active or history of autoimmune disease, or immune deficiency
• Any persistent serious ablation-related complications
• Esophageal and/or gastric variceal bleeding within 6 months
• Inability or refusal to comply with the treatment and monitoring
• Participation in other clinical trials