Treatment outcomes and complications of percutaneous thermal ablation for subcapsular hepatocellular carcinoma

Background : To evaluate treatment efficacy and safety, local tumor progression-free survival (LTPFS), and risk factors for local tumor progression (LTP) after percutaneous thermal ablation for subcapsular hepatocellular carcinomas (HCCs), defined as tumors located not more than 1 cm from the hepatic capsule. Methods : Between January 2011 and December 2020, 55 patients (mean age 66.3 ± 9.2 years) with 67 subcapsular HCCs (mean size 16.3 ± 6.3 mm) underwent percutaneous thermal ablation. We categorized subcapsular HCCs into two groups: surface contact (n = 30) and non–surface contact (n = 37). The non–surface contact group was further divided into those with a closest tumor-to-capsule distance of no more than 5 mm and those with distances greater than 5 mm. Per-lesion technical success, treatment efficacy, LTP, risk factors for LTP, and LTPFS were analyzed and compared. Results : The technical success rate was 95.5% (64 of 67 cases). Primary and secondary technical efficacy rates were 98.5% and 33.3%, respectively, with a local control rate of 54.5%. LTP occurred in 12 of 66 tumors (18.2%) during a median follow-up of 21 months. These outcomes and LTPFS probabilities did not differ significantly between the two major groups or among the non–surface contact subgroups. The major complication rate was 4.5%, all of which were tumor seeding. In univariate analysis, tumor size > 2 cm was a significant risk factor for LTP (P = 0.042, odds ratio 3.91, 95% confidence interval 1.05–14.5). Conclusion : Percutaneous thermal ablation remains a feasible and safe treatment for subcapsular HCCs, with a low major complication rate. The distance between subcapsular tumors and the liver capsule does not appear to limit procedural effectiveness.