Long-term outcomes of radiofrequency ablation for unifocal low-risk papillary thyroid microcarcinoma: a large cohort study of 414 patients.

OBJECTIVES The purpose of this study was to evaluate the long-term efficacy and safety of radiofrequency ablation (RFA) for low-risk papillary thyroid microcarcinoma (PTMC) in a large population. METHODS From June 2014 to December 2017, 414 patients (323 females, 91 males, mean age 43.56 ± 9.79 years, range 18-73 years) with unifocal low-risk PTMC confirmed by core-needle biopsy (CNB) were treated by RFA. Patients were followed up at 1, 3, 6, and 12 months and every 6-12 months thereafter by ultrasound and contrast-enhanced ultrasound (CEUS). The volume and the volume reduction ratio (VRR) were calculated. Recurrence and lymph node or distant metastasis were evaluated. RESULTS The mean initial volume was 92.74 ± 83.43 mm3 (range 4.19-490.07 mm3), which decreased significantly to 1.37 ± 7.94 mm3 (range 0-67.97 mm3) at a mean follow-up time of 42.15 ± 11.88 months (range 24-69 months) with a mean VRR of 98.81 ± 6.41% (range 50-100%). No life-threatening or delayed complications occurred. After RFA, 366 tumors (88.41%) completely disappeared. The overall incidence of local tumor progression rate was 3.62%. Among them, one patient (0.24%) was diagnosed to have residual cancer by CNB and underwent additional RFA. Four patients (0.97%) developed metastatic lymph node, and 10 patients (2.42%) had recurrent PTMC. A total of 13 patients underwent additional RFA, and 11 lesions completely disappeared during the follow-up. CONCLUSIONS RFA is an effective and safety treatment for low-risk PTMC after a long-term follow-up period for a large cohort with careful patient enrollment evaluation. KEY POINTS • Radiofrequency ablation is an effective and safe alternative for low-risk PTMC. • The overall incidence of local tumor progression rate was low. • No life-threatening or delayed complications occurred.