The purpose of this study is to determine the technical success rate of creating a safety margin of 5 mm or more including the tumor by performing image-guided percutaneous microwave thermal therapy using a microwave generator and antenna developed by StarMed for the treatment of small liver cancer and the 1-year local recurrence rate based on follow-up imaging tests.

Study Design and-Purpose: This is a prospective, single-center clinical study to evaluate the effectiveness of microwave ablation (MWA) for treating small liver malignancies using the Starwave™ microwave generator and antenna. The primary purpose is to assess the 12-month local tumor recurrence rate. Secondary objectives include evaluating the technical success of achieving a ≥5 mm safety margin around the tumor, as well as procedural time, ablation volume, and safety.

Background: Hepatocellular carcinoma (HCC) and metastatic liver tumors are major causes of cancer-related death worldwide. For small tumors (≤5 cm), thermal ablation techniques like Radiofrequency Ablation (RFA) and Microwave Ablation (MWA) are common treatment options, especially for patients who are not candidates for surgery. MWA offers several advantages over traditional RFA, including faster ablation times, larger ablation zones, and less susceptibility to the "heat sink" effect from nearby blood vessels. Achieving a sufficient safety margin (5-10 mm) around the tumor is critical to prevent local recurrence.

The Starwave™ MWA system, a domestic product in Korea, can deliver a higher maximum power output (150W) compared to some existing systems (e.g., Emprint™, 100W), potentially enabling more efficient energy delivery and larger, more spherical ablation zones. This study aims to prospectively evaluate the 12-month outcomes of this system, as no such data currently exists.

Eligibility Criteria The study will enroll 128 patients who meet the following key criteria. Inclusion Criteria: 1) Age 20-85 years; 2) Diagnosed with liver malignancy ≤4 cm in size (HCC, metastatic cancer, or recurrent/residual HCC); 3) Child-Pugh class A or B liver function; 4) Provided informed consent.

Exclusion Criteria:1) More than 3 malignant liver tumors; 2)Tumors larger than 4 cm; 3) Diffuse infiltrative type cancer;4) Severe coagulopathy or liver failure (Child-Pugh class C); 5) Tumor invasion into major hepatic vessels; 6) Intervention and Follow-up

Intervention: Patients will undergo percutaneous MWA using the Starwave™ system. The procedure will be performed under image guidance (ultrasound, often with CT/MR fusion imaging) with one or two 13-gauge antennas. The goal is to ablate the tumor and a 5-10 mm safety margin.

Follow-up: A CT or MRI scan will be performed immediately post-procedure to assess technical success. Subsequent follow-up with CT or MRI will occur approximately every 3 months for up to 12 months to monitor for local tumor recurrence.

Outcome Measures

1. Primary Outcome Measure: Local Tumor Recurrence Rate at 12 Months: The percentage of patients with tumor recurrence at the ablation site within 12 months, as assessed by CT or MRI.

2. Secondary Outcome Measures:

   1. Technical Success Rate: The percentage of procedures that achieve complete tumor ablation with a safety margin of at least 5 mm on the immediate post-procedure CT/MRI scan.
   2. Ablation Volume: The volume of the necrosis area created by the MWA procedure.
   3. Procedure Time: Time from the insertion to the removal of the MWA antenna.
   4. Safety: Incidence and severity of procedure-related complications, graded using the Clavien-Dindo classification system.

Inclusion Criteria:

• Child-Pugh Class A or B
• Patients with suspected hepatocellular carcinoma or residual/recurrent hepatocellular carcinoma of 4 cm or less on MDCT, CEUS, or MRI performed within the last 60 days or Patients with suspected metastatic liver cancer of 4 cm or less on MDCT, CEUS, or MRI performed within the last 60 days, for whom microwave thermal ablation is being considered

Exclusion Criteria:

• In cases where there are three or more malignant liver tumors
• When the maximum size of the tumor exceeds 4 cm
• Diffuse infiltrative type of cancer with unclear tumor boundaries
• When the tumor is adhered to the central hepatic portal vein, hepatic vein, or bile duct by 5 mm or more
• Severe liver failure (Child-Pugh Class C)
• In cases of vascular invasion by malignant liver tumors
• Severe coagulopathy (platelet count below 50,000/mm³ or INR prolonged by more than 50%)
• In cases of multiple extrahepatic metastases
• Situations where it is highly unlikely to obtain appropriate data for research purposes