RF Ablation Significantly Reduces Thyroid Nodules in Biggest Study

Nancy A. Melville

May 21, 2018

Monopolar radiofrequency ablation (RFA) shows high efficacy and safety in reducing the volume of benign thyroid nodules while avoiding the need for invasive surgery in a new study.

The authors conclude that "a single treatment course with monopolar RFA 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," say Harald Dobnig, MD, of the Thyroid, Endocrine and Osteoporosis Institute Dobnig, Graz, Austria, and colleagues.

The findings were published in the April issue of Thyroid.

The study of 277 Austrian patients, the largest prospective cohort of benign thyroid nodules treated with a single monopolar RFA treatment to date, showed mean volume reduction rates after 12 months to be as much as 82%, with more than 81% of nodules showing a volume reduction of 70% or more.

Whereas approximately 90% of thyroid nodules do not increase in size over time, those that do grow can present cosmetic as well as functional problems and are commonly treated with surgery.

Thermoablative alternatives such as RFA — though primarily used by just a few research groups worldwide — offer the potential to avoid surgery and conserve normal thyroid function.

"The results of the current study are consistent with the existing literature and confirm the safety of RFA in general and the efficacy of a single treatment course of monopolar RFA in a large central European cohort," write Dobnig and colleagues.

"The results also provide some potentially significant data for future discussions regarding possible selection criteria for patients with thyroid nodules that could be treated with RFA," they add.

Study Included Patients With Larger Thyroid Nodules

In the current study, mean baseline nodule volume (± standard deviation) was 13.8 ± 15 mL, which corresponds to a nodule diameter of 3.0 cm, the authors note. This contrasts with the previous largest study to date, conducted in 200 participants in Asia (AJNR Am J Neuroradiol. 2015;36:1321-1325), which was retrospective and included patients with relatively smaller nodules (mean volume, 5.4 mL).

Almost 300 patients were treated as outpatients at Dobnig's institute with a single RFA session from April 2014 to June 2017. Nodules were visible in 62.8% of patients and 40% had a symptom score of 4 or higher on a 10-point visual analog scale.

Treatment involved an internally cooled 18G RF electrode used with a free-hand "moving-shot" technique after patients received subcutaneous and local peri-thyroidal anesthesia.

Mean overall rates of nodule volume reduction were 68% ± 16% at 3 months and 82% ± 13% at 12 months (P < .001).

In addition to the 81% of nodules with a volume reduction rate of 70% or higher at 12 months, 10% had volume reductions of 60% to 70%, 6% had reductions of 50% to 60%, and only 2% had reductions of 50% or less.

Most nodules were solid or predominantly solid (74.4%), and these nodules had a mean volume of 13.6 ± 15.9 mL. The rest were mixed (12.1%) or cystic/predominantly cystic (13.5%).

Volume Reduction Rates Higher for Smaller and Cystic Nodules

In a subgroup analysis of nodules based on factors including baseline size (≤ 10  mL or > 30  mL), or nodule composition (solid, mixed or cystic), volume reduction rates were significantly higher for smaller and cystic nodules, at rates of 8.8% and 14.5% higher, respectively, than for the other groups at 12 months post-RFA (P < .001).

Importantly, scores on symptoms as well as cosmetic appearance significantly improved at 3 and 12 months (P < .001).

Specifically, the percentage of nodules that were visible with or without neck extension declined from 62.8% prior to RFA to 17.1% at 3 months post-RFA and 7.1% after 12 months.

In addition, the percentage of patients with significant symptoms (visual analog scale ≥ 4) declined from 38.2% to 0%.

Of 32 hyperthyroid patients who had follow-up data available, 27 (84%) became euthyroid, one (3.1%) developed subclinical hypothyroidism, and four (12.5%) had subclinical hyperthyroidism at their last visit.

Although RFA is currently not endorsed in the United States for the treatment of thyroid nodules, the findings add to increasing interest in the modality.

As reported by Medscape Medical News, a smaller recent study of 14 patients treated with a median of eight RFA cycles at the Mayo Clinic, Rochester, Minnesota, showed a mean nodule reduction of 44.6% at a mean follow-up of 8.6 months, with 8 of 12 patients having compressive symptoms resolved and four patients having reduced symptoms.

The authors of that study noted that skill and patient selection are key factors in RFA treatment, with appropriate candidates including those with poor ultrasonographic visualization of the nodule and poor access to the nodule.

The authors have reported no relevant financial relationships.

Thyroid. 2018;28:472-480. Full text

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