| Summary: | 碩士 === 國立臺灣大學 === 臨床醫學研究所 === 106 === Background：
Radiofrequency（RF）ablation is a curative therapy for small hepatocellular carcinoma（HCC）. Although mono-polar electrode with centrifugal ablation method is the mainstream in current clinical practice, a higher local recurrence rate and need of repeated treatment sessions are the main drawbacks of mono-polar RF ablation in comparison with surgical resection. Multi-bipolar RF ablation is a newly developed method for HCC therapy by using multiple bipolar electrodes simultaneously. The concept of “No-touch ablation” enables centripetal ablation of tumor and is the most important technical progress of bipolar electrodes. However, the comparison of long-term treatment outcomes between no-touch multi-bipolar RF ablation and mono-polar RF ablation remains unclear.
Aim：
In this multicenter retrospective study, we aimed to compare the long-term outcomes of no-touch multi-bipolar versus mono-polar radiofrequency ablation for patients with hepatocellular carcinoma ≤4 cm.
Methods：
From January 2010 to December 2017, a total of 385 cirrhotic patients with newly diagnosed HCC in three medical centers were surveyed. The maximal tumor size was 4 cm and the maximal tumor number was three. After propensity score matching for baseline characteristics, a total of 234 patients with 331 tumors were enrolled and allocated equally in both treatment groups.
About 68% of patients had more than one tumor and 82% of tumors were more than 2 cm in diameter（mean：2.66 ± 0.83）. About 22% of tumors were in the subcapsular area which was considered to be a difficult location for RF ablation. For the no-touch treatment group, 2 ~ 5 bipolar electrodes were deployed outside the tumor margin with centripetal ablation. For the mono-polar treatment group, one electrode was applied into the tumor center with centrifugal ablation. Most procedures were performed in the operation room under general anesthesia. Percutaneous approach with ultrasound guidance was used for all of the patients. Contrast-enhanced dynamic computed tomography（CT）or magnetic resonance images（MRI）were performed one month after ablation and every 3 months for one year and every 6 months thereafter.
Kaplan-Meier method was used to assess the survival probability and the Cox proportional hazard method was used to assess the predictive parameters for complete ablation rate, local and distant tumor progression rate and overall survival. Among these endpoints, complete ablation was calculated as per tumor basis and tumor progression as well as overall survival were assessed as per patient basis.
Results：
Complete ablation rate after one session of treatment was 98.2% for the no-touch treatment group and 77.6% for the mono-polar treatment group. Mono-polar method and tumor size > 2 cm were the two predictive factors for incomplete ablation（P<0.001 and 0.001, respectively）. After repeated treatment sessions, there were 2 patients in the no-touch treatment group and 4 patients in the mono-polar treatment group failed to achieve complete ablation of the original index tumor.
After a median follow-up of 2.14 years（range：3 ~ 96 months）, the cumulative 1-year、3-year、5-year local recurrence rate were 4.2%、5.7%、5.7% for the no-touch treatment group, respectively and 30.0%、41.3%、41.3% for the mono-polar treatment group, respectively. Safety margin less than 5 mm , mono-polar method and tumor abutting vessel >3 mm were three significant factors for local tumor progression（P=0.001, P=0.006, P=0.015 respectively）.
The cumulative 1-year、3-year、5-year distant recurrence rate were 12.8%、24.9%、35.9% for the no-touch treatment group, respectively and 36.3%、57.3%、65.6% for the mono-polar treatment group, respectively. Tumor number more than one and safety margin less than 5 mm were the two main factors contributing to distant recurrence（P<0.001）. Mono-polar treatment group also had a higher risk of distant recurrence（P=0.013）.
The 1-year、3-year、5-year overall survival were 93.6%、84.8%、65.3% for the no-touch treatment group, respectively and 91.3%、70.3%、58.0% for the mono-polar treatment group, respectively. Liver reserve of Child-Pugh B class was the most significant factor for poor overall survival.
There was no difference about major complication rate between these two groups （4.27% vs. 6.84%）.
Conclusions：
This is the largest cohort in Asia to compare the long-term outcomes of two commonly used RF ablation methods for treatment-naïve patients with small HCC. No-touch multi-bipolar RF ablation method may provide better disease free survival and less need of repeated treatment sessions with similar complication rate to mono-polar method. Child-Pugh B disease is found to be the most significant factor affecting overall survival in our study. Taken together, no-touch ablation method is not only an effective and safe method to treat small HCC no more than 4 cm but also provides better life quality for HCC patients.
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