Safety and efficacy of radiofrequency ablation for papillary thyroid carcinoma adjacent to the thyroid capsule.

BACKGROUND: Ultrasound-guided radiofrequency ablation (RFA) has become an established minimally invasive treatment for selected patients with low-risk papillary thyroid carcinoma (PTC). However, the safety and efficacy of RFA for PTCs located immediately adjacent to the thyroid capsule (≤2 mm) remain insufficiently characterized because of the increased risk of thermal injury to adjacent critical structures. This study aimed to evaluate the safety and oncologic outcomes of ultrasound-guided RFA for solitary T1N0M0 PTC in this anatomically challenging setting. METHODS: This single-center retrospective study included 303 consecutive patients with solitary PTC located within 2 mm of the thyroid capsule who underwent ultrasound-guided RFA between June 2015 and December 2023. All diagnoses were confirmed by fine-needle aspiration, and all patients declined surgical treatment. Tumors were classified as T1a (n = 263) or T1b (n = 40). The primary efficacy endpoints were technical success and complete tumor disappearance. The primary safety endpoint was the incidence of procedure-related complications. Disease progression was assessed as a secondary endpoint. Patients underwent serial ultrasonographic follow-up according to a predefined protocol. RESULTS: Technical success was achieved in all patients (100%, 303/303). After a median follow-up of 36 months, complete tumor disappearance of the treated tumor was observed in 294 patients (97.0%). The complete disappearance rate was higher in the T1a group than in the T1b group (98.1% [258/263] vs 90.0% [36/40]), and the difference was statistically significant (P <0.001). Disease progression occurred in five patients (1.65%), all in the T1a group, including four cases of newly developed primary thyroid carcinoma and one case of cervical lymph node metastasis. Procedure-related complications occurred in 10 patients (3.3%), all of whom experienced transient hoarseness that resolved spontaneously within 6 months. The complication rate was significantly higher in the T1b group than in the T1a group (10.0% [4/40] vs 2.3% [6/263]; P = .034). BRAFV600E mutation status was not associated with disease progression (P = .99). CONCLUSION: Ultrasound-guided RFA combined with hydrodissection and the lever maneuver is an effective and generally safe minimally invasive treatment option for solitary T1N0M0 PTC located adjacent to the thyroid capsule. Careful patient selection remains essential, as T1b tumors were associated with a numerically lower complete disappearance rate and a significantly higher risk of transient hoarseness compared with T1a tumors.