Thyroid radiofrequency ablation (RFA) has become increasingly used as a thyroid-sparing nonsurgical intervention for thyroid nodules throughout the world. Although the efficacy and safety of this treatment has been well-established for benign thyroid nodules, the use of RFA for papillary thyroid carcinoma (PTC) remains more controversial. In their novel study, Yan et al¹ followed-up a cohort of 179 patients with T1 PTC treated with RFA over 10 years to determine long-term oncologic outcomes and complications. Overall, the results demonstrate the feasibility and safety of the technique in both the short- and long-term periods. The study and results are commendable, and contribute critical data in support of the ablative treatment of appropriately selected thyroid malignant diseases. Herein, we write to add additional context that is important in considering these results.

It should first be noted in this study that the rate of complete disappearance was substantially higher in the T1a group than the T1b group (98.8% vs. 71.4%; difference, 27.4%; 95% CI, 10.2%-53.4%), and that the T1b (>1 cm PTC) cohort was considerably smaller (n = 165 vs 14). Other oncologic outcomes, including disease-free survival and disease progression were similar between the 2 groups. A significant portion of patients required percutaneous core needle rebiopsy of the nodule following ablation, often due to ultrasonographic presence of a persistent nodule (44 patients, 24.5%). Although the rate of malignant disease in these biopsies was reassuringly low, the need for repeat biopsies and continued surveillance of radiographic abnormalities may contribute to ongoing anxiety in some patients. For volumetric perspective, T1a tumors are typically no larger than 0.5 mL, whereas nodule volumes in the T1b category can be up to 8 times greater (up to 4 mL). This significant volume difference intuitively renders complete treatment response more challenging.

Other studies have also noted inferior rates of complete disappearance when ablating larger primary thyroid carcinomas. Most recently, Fei et al² reported a 74.2% volume reduction rate at 12 months in 32 patients with T2N0M0 PTC treated with RFA or microwave ablation (MWA). Hoarseness also notably occurred in 5 patients (14.7%). Similarly, a study by Xiao et al³ using propensity score matching in 262 patients with a minimum of 12 months of follow-up found a large difference in the tumor disappearance rate between T1a and T1b nodules (81.7% vs 52.7%; difference 29.0%, 95% CI, 17.8%-39.2%). Histologic analysis confirmed a higher rate of persistence among T1b tumors. A recent study⁴ demonstrated malignant disease in 12.2% of T1b nodules vs 2.9% of T1a nodules in core needle biopsies of ablation zones following successful ablation. These results are not surprising given the need to extend the ablation zone slightly beyond the visible boundaries of the tumor to ensure complete treatment. This becomes challenging with larger lesions that are more likely to abut critical structures susceptible to thermal damage. The visual obscuration that results from ablation also becomes a more important factor as the size of the treated nodule increases.

Finally, we also remind the readers that outcomes from low-risk T1 PTC, regardless of treatment (including, often, no treatment at all), have been established to be excellent. Indeed, robust data from multidecade follow-up of over 5000 patients did not show meaningful differences in oncologic outcomes between patients undergoing upfront surgery vs active surveillance, and no treatment or disease-related mortality in either group.⁵ Thermal ablation has come to occupy an attractive middle ground in the management of low-risk thyroid malignant diseases, offering an option that is more active than surveillance but less invasive than surgery. Yet, there is still much we have to understand about thyroid ablation, its consequences and best applications. Although complete long-term ultrasonographic disappearance of a primary malignant tumor is the most ideal outcome, this is not attainable in all patients. It also appears less likely with increasing size (T stage) of the initial nodule. Encouragingly, as we see in this study,¹ the presence of a radiographic remnant does not necessarily imply persistence of malignant disease, nor does it portend worse oncologic outcomes. However, its mere existence and the relative uncertainty over its nature and potential necessitate ongoing surveillance and may be a source of patient and physician concern. Particularly in the case of T1b tumors, the physician must critically consider what benefit is being provided to the patient in performing an ablative procedure.

As we continue to debate and collectively decide the appropriate treatment extent for these small differentiated cancers (including total thyroidectomy plus radioactive iodine, total thyroidectomy alone, thyroid lobectomy, percutaneous ablation, and active surveillance), RFA should certainly play a role and is supported by this study. The growing body of literature addressing long-term oncologic and quality of life outcomes for each approach will further define the patient, tumor, and treatment factors that should drive decision-making in this complex paradigm.

Corresponding Author: Julia E. Noel, MD, Santa Clara Valley Medical Center, Department of Otolaryngology–Head & Neck Surgery, Stanford University School of Medicine, 751 S Bascom Ave, San Jose, CA 95128 (jnoel@stanford.edu).

Published Online: November 7, 2024. doi:10.1001/jamaoto.2024.3563

Conflict of Interest Disclosures: Dr Wrenn discloses that he has received reimbursement and honorarium from StarMed USA for teaching an RFA course. Dr Noel discloses that she serves as a consultant for Pulse Biosciences and Medtronic.