Oligometastasis is a definition that has been described in the past in the 1990s, and in some patients, metastases are not extensive and are limited to a small number of metastases. The local ablative treatment for oligometastasis is not a new concept. In case of liver metastasis from colorectal cancer, long-term survival can be expected if the liver resection is performed. Effectiveness has been demonstrated in studies of adrenal and brain metastasis from lung cancer as well as lung metastasis from sarcoma. A recent non-randomized study reported that patients with oligometastasis improved treatment outcomes with aggressive treatment. This study demonstrated that local ablative treatment for oligometastasis showed better treatment outcomes than expected. Also, the long-term outcomes in SABR-COMET trial showed that the overall survival were increased by 22 months. So far, the standard treatment for metastatic disease is systemic chemotherapy. However, based on these results from studies, active local treatment for patients with oligometastasis is currently being performed in the clinic. In this study, we aimed to apply this concept to patients with hepatocellular carcinoma. To confirm the efficacy and safety of stereotactic radiotherapy in patients with oligometastasis hepatocellular carcinoma

Inclusion Criteria:

i. 19 years or older

ii. Patients who signed the informed consent form

iii. The clinical trial protocol can be complied with at the discretion of the investigator

iv. Performance status (based on ECOG) less than 2 (0, 1)

v. Patients with life expectancy greater than 3 months

vi. Condition in which primary cancer is controlled

• Definition: A condition that has not progressed at the time of review of clinical trials after curative treatment of primary cancer 3 months ago

vii. Number of metastatic lesions up to 5

viii. 3 or less metastatic lesions in one metastatic organ

ix. Those who are undergoing targeted therapy or chemotherapy can also be included (during radiation therapy, drug treatment is stopped)

Exclusion Criteria:

i. Serious medical complications that cannot proceed with radiation therapy

ii. Previous radiation therapy history at the location where radiation therapy is to be performed

iii. malignant pleural effusion

iv. When the spinal cord and the tumor are close (the tumor is located within 3 mm)

v. In case of brain metastasis requiring surgical intervention

In case that individual participant data is being shared, the study protocol is planned to be shared.