PULSAR Radiotherapy Combined With Immunotherapy for High-Risk Advanced Liver Cancer

Inclusion Criteria: * Age 19 years or older * Hepatocellular carcinoma diagnosed histologically or clinically according to the Korean Liver Cancer Association-National Cancer Center guidelines * Unresectable and/or locally advanced or metastatic disease, currently receiving or scheduled to receive immune checkpoint inhibitor-based systemic therapy (e.g., atezolizumab plus bevacizumab or durvalumab plus tremelimumab) * At least one of the following high-risk features: * Tumor larger than 5 cm in maximum diameter * Portal vein tumor thrombosis (Vp2-4) * Infiltrative lesion * Bile duct invasion * Inferior vena cava invasion * Extrahepatic metastasis * At least one measurable target lesion per RECIST version 1.1, with PULSAR already planned by the treating physician * ECOG performance status 0-1 * Child-Pugh score 7 or lower * Known hepatitis B and C virus status, with antiviral therapy per institutional policy if indicated * Voluntary written informed consent Exclusion Criteria: * Pregnant or breastfeeding women * Active brain or leptomeningeal metastases * More than 5 extrahepatic metastatic lesions (multiple intrahepatic lesions are allowed) * Prior radiotherapy to the treatment site * Moderate or refractory ascites, or hepatic encephalopathy * Contraindications to immune checkpoint inhibitors, such as active autoimmune disease requiring systemic treatment (hypothyroidism stable on hormone replacement and type 1 diabetes controlled with insulin are allowed) * Uncontrolled serious comorbidities (e.g., uncontrolled infection, NYHA class II or higher heart disease, myocardial infarction or stroke within 3 months, unstable angina or arrhythmia) * Unable to comply with the study protocol * Considered unsuitable for the study by the investigator