Long-term follow-up of the radiofrequency ablation of benign thyroid nodules: the value of additional treatment

Abstract

Purpose: This study aimed to evaluate the efficacy of additional radiofrequency ablation (RFA) treatment for benign thyroid nodules.

Methods: Electronic medical records at a single institution from September 2008 to August 2016 were searched, and consecutive patients treated with RFA due to benign thyroid nodules with cosmetic or symptomatic problems were enrolled. All patients were followed up for at least 30 months. The nodules were divided into three groups: group 1 included nodules that met the criteria for additional treatment and underwent additional treatment, group 2 included nodules that met the criteria but did not undergo additional treatment, and group 3 included nodules that did not meet the criteria. The ablation results were compared among the three groups in terms of the initial ablation ratio (IAR) and volume reduction ratio (VRR).

Results: Ninety nodules from 88 patients were included in the study. At the last follow-up, group 1 showed a significantly smaller nodule volume and larger VRR (2.5 mL and 84.6%, respectively) than group 2 (8.1 mL and 39.8%, respectively, P<0.001), but did not present a significant difference from group 3 (0.9 mL, P=0.347, and 92.8%, P=0.238). The IAR was significantly higher in group 3 (94.5%) than in the other two groups (group 1, 81.1%; group 2, 82.8%; P<0.001).

Conclusion: Multiple treatment sessions achieve greater VRR. Therefore, additional treatment could be considered for patients who meet the corresponding criteria.

Keywords: Radiofrequency ablation; Thyroid gland; Thyroid nodule.

Fig. 1.. Diagram showing changes in the Vt, Va, and Vv.

Here, initial means the status immediately after RFA. Va shows a decreasing pattern during the follow-up period, and the slope is steep during the first year and there is little change in the slope thereafter. Vt shows a decreasing pattern until about 3 years and shows a slight increase afterward. Vv is relatively stable up to 3 years. However, it increases slightly thereafter. Vt, total volume; Va, ablated volume; Vv, viable volume; RFA, radiofrequency ablation.

Fig. 2.. Diagram showing changes in Vt according to the groups.

Group 1 show declining curve during follow-up period, while group 2 show a volume increase 2 years after RFA. Group 3 show a declining curve during 4 years, but its volume increased slightly at 5 years. Vt, total volume; RFA, radiofrequency ablation.

Fig. 3.. Symptom score and cosmetic score in the three groups during follow-up.

All three groups show improvement in symptoms and cosmetic problems at the final follow-up compared to the initial score. However, group 2 show aggravation in symptom and cosmetic score at 5 years after radiofrequency ablation.

Fig. 4.. Diagram and US images immediately after RFA and at the first follow-up.

Diagram (A) and US image (B) show a nodule immediately after RFA. As there is marked swelling due to the hemorrhage and edema, an accurate measurement of both Vt_initial and Va_initial is not possible. Diagram (C) and US image (D) show the nodule at the first follow-up. The swelling has been absorbed and measurements can be made accurately. The arrows and arrowheads in D indicate the deeper margins of Vt and Va, respectively. IAR, initial ablation ratio; RFA, radiofrequency ablation; US, ultrasonography; Va, ablated volume; Vt, total volume; Vv, viable volume.