为了比较经皮射频消融（RFA）在包膜下和非包膜下位置对单个直径≤3cm的肝细胞癌（HCC）的安全性和疗效，使用倾向评分匹配分析。此回顾性研究纳入了2005年至2015年在两个大型肝脏中心以RFA作为初次治疗的单个直径≤3cm的孤立性HCC患者。患者被分为两组，即包膜下和非包膜下肿瘤位置的患者。在倾向评分匹配前后，比较了这两组患者在合并症、局部肿瘤进展（LTP）和总生存率（OS）方面的差异。研究对象包括964名患者（712名男性[74%]），平均年龄为58.3岁。在这964名患者中，561名（58%）有非包膜下HCC，403名（42%）有包膜下HCC。倾向评分匹配生成了402对患者。虽然较低，但包膜下组的重要并发症发生率显著较高（p = 0.047）。这两组的技术有效率分别为99%和98%（p = 0.315）。然而，在随访期间，无论是在整体队列还是在倾向评分匹配队列中，1年、3年、5年和10年的LTP和OS率在两组中都有显著差异，非包膜下组分别为8%、15%、20%和26%，而包膜下组分别为13%、24%、30%和31%（p = 0.015），两组分别为99%、91%、80%和59%以及98%、85%、73%和50%（p = 0.004）。在对单个直径≤3cm的肝细胞癌进行初次RFA治疗时，主要并发症、LTP和OS的发生率显著有所不同，非包膜下位置效果更好。这项大规模研究提供了证据，表明对于小于等于3cm的肝细胞癌，射频消融在非包膜下位置比包膜下位置更安全、更有效。• 关于早期肝细胞癌的RFA疗效存在相互矛盾的结果，取决于肿瘤位置。• 在包膜下肝细胞癌中，局部肿瘤进展率显著较高。• 包膜下肝细胞癌的总生存率显著较低。©2023年。作者，欧洲放射学学会独家许可。

To compare the safety and efficacy of RFA for single HCCs ≤ 3 cm in subcapsular versus nonsubcapsular locations using a propensity score matched analysis.This retrospective study included patients with solitary HCCs ≤ 3 cm in size who underwent percutaneous RFA from 2005 to 2015 as initial treatment at two large-volume liver centers. Patients were divided into two groups, consisting of those with subcapsular and nonsubcapsular tumor locations. Complications, local tumor progression (LTP), and overall survival (OS) were compared in these two groups before and after propensity score matching (PSM).The study population consisted of 964 patients (712 men [74%]) of mean age 58.3 years. Of these 964 patients, 561 (58%) had nonsubcapsular and 403 (42%) had subcapsular HCCs. PSM generated 402 pairs of patients. Major complication rate was low, but significantly higher in the subcapscular group (p = 0.047). Rates of technical effectiveness in these two groups were 99% and 98%, respectively (p = 0.315). However, during follow-up, cumulative 1-, 3-, 5-, and 10-year LTP and OS rates did significantly differ in both entire and PSM cohorts, resulting in the latter 8%, 15%, 20%, and 26% in the nonsubcapsular group vs. 13%, 24%, 30%, and 31% in the subcapsular group (p = 0.015), and 99%, 91%, 80%, and 59% vs. 98%, 85%, 73%, and 50% in the two groups (p = 0.004), respectively.Rates of major complications, LTP, and OS differed significantly following first-line RFA treatment of single HCCs ≤ 3 cm in favor of the nonsubcapsular locations.This large-scale study provides evidence that radiofrequency ablation for small (≤ 3 cm) hepatocellular carcinomas is safer and more effective in nonsubcapsular location than in subcapsular location.• There exist conflicting outcomes on the effectiveness of RFA for early HCC depending on tumor location. • Rate of local tumor progression was significantly higher in the subcapsular hepatocellular carcinomas. • Overall survival rate was significantly poorer in the subcapsular hepatocellular carcinomas.© 2023. The Author(s), under exclusive licence to European Society of Radiology.