RF Ablation Effective for Large Benign Thyroid Nodules in US Study

Nancy A Melville

March 28, 2018

The use of radiofrequency ablation (RFA) for the treatment of large, benign thyroid nodules, a common practice in other countries but not endorsed in the United States, substantially and safely reduces nodule volume without compromising thyroid function, according to a retrospective review of patients at the Mayo Clinic.

"The present experience confirms that ultrasound-guided RFA is a clinically effective and safe outpatient treatment in patients with symptomatic or steadily growing benign, large, predominantly solid thyroid nodules, reproducing the experience generated in European and Asian studies," the authors write.

"In centers with appropriate expertise, this technique could become an alternative for the management of benign large toxic and nontoxic thyroid nodules."

In the study published online March 21 in Mayo Clinic Proceedings, Oksana Hamidi, DO, Mayo Clinic, Rochester, Minnesota, and colleagues reported that the use of RFA in 14 patients with predominantly solid thyroid nodules resulted in a mean nodule volume reduction of 44.6% at a median follow-up of 8.6 months. In addition, 8 of 12 patients had resolution of compressive symptoms and 4 patients had a reduction in symptoms. There were no adverse effects on thyroid function.

"These results are consistent with data from multiple studies performed outside North America," the authors said.

The majority of thyroid nodules are benign and can be managed with observation, as is recommended in the 2015 American Thyroid Association guidelines. However, the nodules can occasionally grow to the point of causing compressive symptoms and cosmetic concerns.

In such cases, thyroid surgery is the conventional treatment, however the risks of surgery deter some patients while others may not be suitable candidates.

RFA has gained favor in recent years outside of the United States as a well-tolerated alternative to surgery. In randomized clinical trials in South Korea and Italy, researchers saw 50% to 80% volume reductions for thyroid nodule volumes with RFA, with results sustained for at least 3 years.

Hamidi and colleagues note that starting in 2013, physicians have been offering RFA treatment to patients with large (3 cm or greater), predominantly solid tumor nodules that were increasing in size or causing compressive symptoms or cosmetic concerns.

The retrospective review of the center's experience included 14 patients treated between 2013 and 2016, with a median age of 60 years and a median baseline thyroid nodule volume of 24.2 mL (interquartile range [IQR], 17.7–42.5 mL).

Of the patients, 13 had multinodular goiter and 1 had a single thyroid nodule. The nodules were increasing in size in 10 of the 14 patients, with a median increase of 114% (IQR, 49%–148%) over a median of 51 months (IQR, 29–107 months).

Twelve of the nodules were causing compressive symptoms and 8 were causing cosmetic concerns.

Each of the nodules was ablated with a median of 8 radiofrequency ablation cycles (IQR, 6–13).

The median reduction in tumor nodule volume was 44.6% (IQR, 42.1%–59.3%) during a median follow-up of 8.6 months.

At 0 to 3 months follow-up, the median volume decrease was 36.8%; at 3 to 6 months, 43.9%; at 6 to 12 months, 44.2%; at 12 to 24 months, 54.3%; at 12 to 24 months, 54.3%; and at more than 24 months, 52.8%.

The compressive symptoms of the neck or dysphagia resolved in 67% (8 of 12) of patients and improved in the remaining 33%. All 8 patients with cosmetic concerns saw improvements after treatment.

Of the 14 patients, 13 had normal thyroid function prior to their RFA treatment, with 2 taking levothyroxine replacement for primary hypothyroidism. During the follow-up period, there were no changes in the patients' thyroid function test parameters.

One patient had subclinical hyperthyroidism as the result of a toxic adenoma, however thyroid function was normal at 4 months following ablation of the toxic nodule.

RFA Safe, Well-Tolerated

In terms of safety, 1 patient developed hypotension following the ablation procedure, which was attributed to a vasovagal response resulting from the thyroid nodule's deep posterior location. The patient was dismissed the following day without any residual hemodynamic changes.

In addition, 3 patients developed mild neck discomfort, swelling, bruising, and dysphagia that resolved completely within 2 to 5 days of the procedure.

The RFA treatment was well-tolerated and no patients have had a thyroidectomy following the procedure. "During follow-up, all the patients expressed overall satisfaction with the decision to undergo the procedure," the authors said.

Whereas other studies on RFA for large thyroid nodules report maximum benefits of 69% to 90%, the median reduction in the current series was lower at 45%, with most of the reduction achieved in 6 months. The authors speculated that the discrepancy is possibly because of the number of RFA procedures per nodule and the total energy delivered per procedure.

And while at least one previous study showed a link between smaller thyroid nodules (12 mL or less) and response to RFA, the new study showed no factors that correlated with volumetric reduction.

Safety Compared to Thyroid Surgery

The authors note that whereas there were no disruptions in thyroid function associated with RFA, surgical therapy for nodular thyroid disease is linked to a significant risk of hypothyroidism, with thyroid hormone replacement required in approximately 15% to 20% of patients following thyroid lobectomy for benign thyroid disease.

Recurrent laryngeal nerve injury, though uncommon, is also a risk with lobectomy, occurring in 1% to 2% of patients, and post-surgical scarring is also a cosmetic concern for some patients.

With widely varying reports of potential regrowth of treated nodules after RFA, ranging from 5.6% to 24.1%, beginning 1 to 2 years after ablation, the authors say they plan to continue to monitor outcomes in their patient population.

Skill, Patient Selection Key

The authors underscore that skill and patient selection are essential for the procedure's success.

"As discussed in multiple studies, patient selection for RFA is important. The technique requires a substantial amount of experience and expertise with specific training in this procedure," the authors write.

Factors that can suggest patients may not be good candidates for the approach include if ultrasonographic visualization of the nodule of interest is poor and if the nodule cannot be easily accessed.

"Combining the efficacy and safety data with patients' medical limitations and cultural preferences will be an ongoing process to understand the potential role of this procedure in US clinical practice as RFA evolves into an attractive approach for the therapy of large compressive or toxic thyroid nodules," the authors conclude.

The authors have reported no relevant financial relationships.

Mayo Clin Proc. Published online March 21, 2018. Abstract

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