Clinical outcomes of radiofrequency ablation for multifocal papillary thyroid microcarcinoma versus unifocal papillary thyroid microcarcinoma: a propensity-matched cohort study.

Objective: To investigate and compare the clinical outcomes of radiofrequency ablation (RFA) for multifocal papillary thyroid microcarcinoma (PTMC) versus unifocal PTMC in a large cohort. Methods: Patients with low-risk PTMC (n = 487) who underwent RFA were included in this retrospective study and divided into the unifocal group (U group) (n = 432) and the multifocal group (M group) (n = 55) according to the number of lesions. After 1:1 propensity score matching (PSM), volume, volume reduction ratio (VRR), the development of local tumor progression including lymph node metastasis (LNM), recurrent PTMC and persistent lesions, and recurrence-free survival (RFS) rate were evaluated and compared between the two groups. The different impacts of multifocality on recurrence after RFA for PTMC were investigated by Cox analysis. Results: During a mean follow-up time of 49.25 ± 12.98 months, the overall VRR was 99.40 ± 4.43% and the overall incidence of local tumor progression was 3.70% (18/487). No complications occurred after RFA. After PSM, no significant differences were found in volume (0.11 ± 0.69 mm3 vs 0 mm3, p = 0.441), VRR (99.87 ± 0.78% vs 100%, p = 0.441), complete disappearance rate (95.61% vs 89.09%, p = 0.201), incidence of local tumor progression (5.45% vs 5.45%, p = 1.000), LNM (1.82% vs 0%, p = 0.317), recurrent PTMC (1.82% vs 5.45%, p = 0.611), persistent lesions (1.82% vs 0%, p = 0.317), and RFS rate (96.36% vs 94.55%, p = 0.632) between the M group and U group. The association between multifocality and local tumor recurrence also remained nonsignificant (p = 0.619). No distant metastasis or delayed surgery occurred. Conclusions: The impact of multifocality on the prognosis after RFA for low-risk PTMC was little. RFA might be a promising treatment for both unifocal and multifocal PTMC in properly selected patients after sufficient preoperative evaluation. Key Points: • No significant differences are found in the local tumor progression between the unifocal PTMC and multifocal PTMC. • Multifocality is not associated with higher recurrence after RFA for low-risk PTMC. • RFA is a promising alternative for both unifocal and multifocal PTMC. [ABSTRACT FROM AUTHOR]