Preliminary Study of Microwave Ablation for Multifocal Papillary Thyroid Microcarcinoma in Nonoperative Candidates.

Purpose: To study the feasibility, safety, and effectiveness of microwave ablation (MWA) in patients with multifocal papillary thyroid microcarcinoma (PTMC). Materials and

Methods: This retrospective study included patients who underwent MWA for multifocal PTMC (number of nodules ≤3). A total of 44 patients were included, and the mean age was 43 years (SD ± 11). After ablation, progression-free survival (PFS) at 6, 12, 24, 36, and 48 months; disease progression; change in tumor size and volume; tumor disappearance rate; and adverse events (AEs) were assessed, and the feasibility, safety, and effectiveness of MWA for PTMC were evaluated on the basis of statistical analysis.

Results: The median follow-up period was 18 months (interquartile range, 12-33 months). The PFS rates at 6, 12, 24, 36, and 48 months were 100.0%, 96.4%, 96.4%, 70.3%, and 52.7%, respectively. The disease progression rate was 11.4% (5 of 44 patients). The maximum diameter (MD) and volume of the ablation zone were larger at the 3-month follow-up than before ablation (median MD, 13.0 vs 7.0 mm; P < .001; median volume, 503.8 vs 113.0 mm3; P < .001). Subsequently, the tumors exhibited a reduction in both size and volume after 18 months (median MD, 4.0 vs 7.0 mm; P = .04; median volume, 12.6 vs 113.0 mm3; P = .055). At the end of the follow-up period, the complete response rate was 59% (26 of 44 patients). The overall AE rate was 6.8%.

Conclusions: MWA is a feasible treatment for PTMC (number of nodules ≤3), and this study preliminarily demonstrated the safety and effectiveness of this technique.