Microwave Ablation a Safer Option for Multifocal Papillary Thyroid Carcinoma?

The use of microwave ablation to treat ultrasound-detected, multifocal papillary thyroid carcinoma (PTC) was associated with the same outcomes but fewer complications compared with surgical resection, according to results from a Chinese retrospective, multi-center study.

Progression-free survival (PFS) was comparable between the two groups, with 1-, 3-, and 5-year rates for microwave ablation versus surgical resection groups of 98.7% and 98.5% (P=0.39), 91.5% and 95.0% (P=0.26), and 77.2% and 83.1% (P=0.36), respectively.

Overall risk of disease progression was 4.8% with microwave ablation and 3.5% with surgery (P=0.42), reported Ming-An Yu, MD, of the China-Japan Friendship Hospital in Beijing, and colleagues, in Radiology.

As for the major complications associated with treating thyroid cancer, transient hoarseness occurred in 3.1% of patients who underwent microwave ablation and 7.5% of those who underwent surgical resection, with recovery within 3 months. Permanent hoarseness (2.2%) and permanent hypoparathyroidism (4.0%) were reported only in the surgical resection group.

In an editorial accompanying the study, Christos Georgiades, MD, PhD, of Johns Hopkins University in Baltimore, said the bad news is that 35.5% of the patients in the surgical resection group who were initially classified as having T1N0M0 (organ-confined disease) PTC were found to have lymph node metastases and had their cancer reclassified as T1N1M0 after neck dissection.

“This suggests that ablative treatment of multifocal, organ-confined (at imaging) PTC may potentially undertreat 35.5% of patients,” he wrote. The good news, he added, is that “despite the risk of residual nodal disease after ablative treatment the investigators found no difference in oncologic outcomes.”

Georgiades added that there are currently no uniformly accepted treatment guidelines for PTC, and that most professional associations “lukewarmly, albeit sometimes indirectly, support surgery.”

Considering the indolent nature and generally favorable prognosis of the disease, as well as the risk of complications with surgery, it is likely that many patients with PTC are being overtreated, he said. “Ablative modalities should be considered.”

PTC is the most common type of thyroid cancer and often presents with multifocality (two or more separate foci within the thyroid gland).

While microwave ablation has shown promising efficacy as a less invasive option than surgery that could preserve thyroid function, the authors pointed out that only a few small studies have thoroughly evaluated these modalities for multifocal PT, precluding a definitive conclusion regarding the safety and efficacy of microwave ablation in this setting.

This retrospective study included 775 patients with preoperative ultrasound-detected T1N0M0 multifocal PTC treated at 10 centers in China from May 2015 through December 2021.

After propensity score matching, 229 patients (median age 44 years, 179 female) in the microwave ablation group and 453 patients (median age 45 years, 367 female) in the surgical resection group were observed for a median of 20 months and 26 months, respectively.

In the surgery group, the majority (54.7%) underwent total thyroidectomy, while 35% underwent hemithyroidectomy and 9.9% underwent subtotal thyroidectomy.

The authors found that microwave ablation was associated with shorter procedure times (median 30 vs 90 minutes) and hospitalization durations (median 3 vs 5 days).

Furthermore, estimated blood loss was lower in the microwave ablation group than the surgical resection group (median 1 vs 10 mL), and incision length was also shorter for microwave ablation compared with surgical resection (median 0.4 vs 7 cm).

In addition to the major complications described above, minor complications included hematoma requiring surgical hemostasis and infections, both of which were seen only in the surgical resection group (0.4% in both cases).

Transient hypoparathyroidism occurred in 17.0% of patients in the surgical resection group, resolving within 6 months with oral vitamin D and calcium supplementation.

Limitations included the fact the study was retrospective, resulting in likely selection bias, and that follow-up time was relatively short.

“The follow-up period was short considering the natural history of this disease (20 months for microwave ablation vs 26 months for surgical resection), although some patients were observed for up to 10 years,” Georgiades wrote. “Nonetheless, it is reassuring that the outcomes in this study mirror those in studies with far longer follow-up periods.”

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