Monopolar Radiofrequency Ablation of Thyroid Nodules: A Prospective Austrian Single-Center Study

Abstract

Background: Monopolar radiofrequency ablation is currently deemed an exotic treatment option for benign thyroid nodules in many central European countries. The aim of this study was to evaluate prospectively the safety and efficacy of this method in a large patient cohort following its introduction in Austria.

Methods: Peri- and post-interventional complications were analyzed for 277 patients. Efficacy was determined for 300 and 154 nodules at 3 and 12 months post treatment, respectively. All treatments were performed with an internally cooled 18G radiofrequency electrode using a free-hand, "moving-shot" technique following subcutaneous and local perithyroidal anesthesia.

Results: Mean patient age (SD) was 52 ± 12.9 years (75% female), and overall mean baseline nodule volume (SD) was 13.8 ± 15.9 mL. Nodules were visible in 62.8% of patients, 40% had a symptom score ≥4 on a 10-point visual analogue scale, and 14.4% had hyperthyroidism. Mean overall nodule volume reduction rates (VRR) at 3 and 12 months were 68 ± 16% and 82 ± 13%, respectively (p < 0.001). At 12 months, 81% of nodules exhibited a VRR of ≥70%, with 10%, 6%, and 2% of nodules showing VRRs of 60-70%, 50-60%, and ≤50%, respectively. Subgroup analysis according to baseline nodule size (≤10 mL to >30 mL) or baseline nodule composition (solid, mixed, cystic) revealed significantly higher VRRs for smaller and cystic nodules. Moreover, nodule shrinkage was accompanied by significantly improved symptom and cosmetic scores after 3 and 12 months (p < 0.001). Of 32 hyperthyroid patients, 27 (84%) were euthyroid, four had subclinical hyperthyroidism, and one had subclinical hypothyroidism at last follow-up. Post-procedural complications were absent in 83% of patients, minimal in 12.9%, moderate and reversible in 3.2% (1.8% voice change, 0.7% hyperthyroidism, 0.3% wound infection treated with antibiotics, 0.3% epifascial hematoma), and irreversible in 0.7% (one case with hypothyroidism and one with a wound infection treated by surgery).

Conclusions: It is concluded that a single treatment course with monopolar radiofrequency ablation is both safe and highly effective in terms of nodule volume reduction, relief of local symptoms, and (in patients with hyperthyroidism) restoration of euthyroid function. In no case was a prescription of thyroid medication required among those patients who were euthyroid at baseline.

Keywords: RFA; cystic nodule; nodule shrinkage; thermal ablation; thyroid nodule; toxic nodule.

FIG. 1.

Subgroup analysis of nodule volume reduction ratio at 3 and 12 months according to different baseline nodule characteristics based on initial size and nodule composition (mean ± SD).

FIG. 2.

The graph shows nodule VRR for consecutively treated nodules at 3 and 12 months since introduction of the RFA method. Analysis of variance was significant for VRR at three months (p = 0.01) but not at 12 months (p = 0.08). The trend over time suggests a VRR difference of approximately 10% and a learning curve for monopolar RFA that reached a plateau quite early.

FIG. 3.

Percentage of patients and their outcomes in terms of volume reduction ratio (VRR) and cosmetic and symptom scores at baseline and at 3 and 12 months. Cosmetic score: CS 0, no palpable nodule; CS 1, nodule palpable; CS 2, nodule visible during swallowing and/or neck extension; CS 3, nodule easily visible. Symptom score was measured using a visual analog scale (0–10). Nodule volume reduction categories were significantly different between 3 and 12 months. Cosmetic and symptom scores at 3 and 12 months were significantly different from baseline scores, as well as from each other (p < 0.001).

FIG. 4.

Individual results of hyperthyroid patients at baseline and development of volume of toxic nodules and TSH values over time. Approximately half of patients had antithyroid medication at baseline, none at follow-up. Of 32 patients with follow-up measurements, 27 (84.3%) were euthyroid at last visit, one (3.1%) patient developed subclinical hypothyroidism, and four had subclinical hyperthyroidism (all had manifest hyperthyroidism at baseline).