Tumor Thrombosis

This is a single-center, single-arm, open-label study that includes patients meeting the inclusion criteria (liver-GTV volume \< 700ml or estimated liver-GTV V5 \< 300ml) with hepatocellular carcinoma with diffuse tumor thrombosis involving both left and right lobes. All lesions receive moderate-dose hypofractionated intensity-modulated radiotherapy, with a gross tumor dose of 25Gy/5f, and a maximum dose of 35Gy/5f at the tumor center. One week before or during the radiotherapy, patients receive concurrent Pembrolizumab at a dose of 200mg. Subsequently, Pembrolizumab is administered intravenously every 3 weeks. Follow-up examinations are conducted 1-3 months post-radiotherapy. Lenvatinib 4mg may be used for maintenance therapy with Pembrolizumab if there are no contraindications. Maintenance therapy is continued until disease progression or intolerance. The primary endpoint is median overall survival (mOS), and secondary endpoints include objective response rate (ORR), progression-free survival (PFS), and toxicity.