Radiofrequency Ablation of Calcified Papillary Thyroid Microcarcinoma: Long-Term Imaging Evolution and Clinical Outcomes

Background: Radiofrequency ablation (RFA) is a minimally invasive treatment for low-risk papillary thyroid microcarcinoma (PTMC). Although intratumoral calcification is a common feature of papillary thyroid carcinoma (PTC), its impact on RFA efficacy remains unclear. We aimed to evaluate the technical feasibility, clinical outcomes, and pattern-specific course of calcification resolution with RFA for PTMC. Methods: This retrospective study included 258 consecutive patients with low-risk, unifocal PTMC who underwent RFA between November 2017 and August 2022. Intratumoral calcification was classified on ultrasonography as microcalcification, macrocalcification, rim calcification, or mixed calcification. The primary outcomes were technical success and calcification disappearance rates by calcification pattern. Secondary outcomes included serial volume reduction ratio (VRR), cumulative disease progression, local tumor recurrence, and complications. Results: Among 258 PTMCs, 94 had calcifications (68 microcalcifications, 12 macrocalcifications, 14 rim calcifications) and 164 had none. Mean follow-up was 53.5 ± 16.7 months. Technical success was achieved in all patients in both groups. By 18 months, mean VRR exceeded 90% in both groups, and all tumors achieved 100% VRR at the final follow-up (≥36 months). Cumulative disease progression occurred in one patient (0.4%, lymph node metastases at ipsilateral neck level IV and VI), and 15 patients (5.8%) developed new PTC in the remaining thyroid; the rates did not differ between groups. Among PTMCs with calcifications, complete disappearance of calcification occurred in 90 cases (90/94, 95.7%) after 14.2 ± 12.3 months. Disappearance rates were highest for microcalcifications (100%), followed by rim calcifications (92.9%) and macrocalcifications (75.0%). Microcalcifications were resolved significantly faster (mean, 12.0 months), whereas rim calcifications were resolved the slowest (mean, 24.8 months; p < 0.001). The solid component and calcification resolved concurrently in 75.5% of tumors. One minor complication (transient hoarseness, 0.4%) occurred, and no major or delayed complications were observed. Conclusions: In this retrospective cohort, RFA achieved complete resolution of the viable soft-tissue component with a low complication rate in low-risk PTMC, both with and without intratumoral calcification. Technical success was achieved in 100% of tumors regardless of calcification status, and no significant difference in outcomes was observed between the calcified and noncalcified groups. These findings suggest that intratumoral calcification does not preclude effective ablation.