RFA of Cervical Thyroid Cancer Metastases

In This Article

Abstract and Introduction

Abstract

Context: Radiofrequency ablation (RFA) is used in the United States to treat benign thyroid nodules; however, experience with treating cervical recurrence/persistence of papillary thyroid cancer (PTC) is limited.

Objective: To evaluate the efficacy RFA for the treatment of cervical recurrence/persistence of PTC in the United States.

Methods: This is a retrospective, multicenter study of 8 patients who underwent RFA of 11 cervical metastatic PTC lesions between July 2020 and December 2021. The volume reduction (VR) of the lesions, thyroglobulin (Tg) levels and complications following RFA were assessed. Energy applied per unit volume (E/V) during RFA was also determined.

Results: Nine out of 11 (81.8%) lesions had initial volume under 0.5 mL and showed a complete (n = 8) or near-complete (n = 1) response. The 2 lesions with initial volume over 1.1 mL had a partial response, 1 of which had regrowth. There was a median VR of 100% (range 56.3–100%) after a median follow-up period of 453 days (range 162–570 days), with corresponding decline in Tg levels from a median of 0.7 ng/mL (range 0–15.2 ng/mL) to a median of 0.3 ng/mL (range 0–1.3 ng/mL). All patients with an E/V of at least 4483 J/mL or higher had a complete or near-complete response. There were no complications.

Conclusion: RFA performed in an endocrinology practice is an efficacious treatment option for selected patients with cervical metastases of PTC, particularly those who cannot or do not want to undergo further surgery.

Introduction

Well-differentiated thyroid cancer generally has a favorable prognosis; however, depending on risk factors, the incidence of structural recurrence ranges from 1% to 55%.^[1–3] More than 90% of recurrences of papillary thyroid cancer (PTC) are in the neck and cervical lymph nodes.^[3,4] The conventional treatment options for metastatic thyroid cancer include surgery and radioiodine therapy. Repeated surgeries in the neck can lead to complications such as fibrosis, hypoparathyroidism, vocal cord paralysis, and alteration of normal tissue architecture.^[5,6]

In cases of recurrent thyroid cancer in the neck where the patient is not a surgical candidate, the current American Thyroid Association (ATA) guidelines suggest the use of radiofrequency ablation (RFA).^[7] RFA is a minimally invasive procedure that has been used to treat benign thyroid lesions and recurrent thyroid neoplasms.^[8–12] RFA has been shown to be safe and effective in the management of metastatic cervical lymph nodes secondary to PTC in literature from South Korea and China.^[4,10,11]

Despite the increasing popularity of thermal ablation techniques being used to treat thyroid nodules and recurrent thyroid cancer in the United States, clinical data on efficacy and safety of RFA in the management of metastatic thyroid carcinoma to cervical lymph nodes remain extremely limited.

The first reported use of RFA in the United States for cervical recurrence of thyroid carcinoma was in 2001 at Brown Medical School, Rhode Island Hospital, Providence, where 8 patients (7 with PTC, and 1 with follicular thyroid carcinoma) were treated, with long-term follow-up reported in 2006 with 16 patients (15 with PTC, and 1 with medullary thyroid cancer), and in 2013 with 21 patients; after which only case reports have been published.^[13–17] Table 1 summarizes the international studies on RFA used to treat cervical metastases from PTC.^{[10,11,18–24]} A limited number of case reports with successful outcomes have also been published.^[25,26]

This retrospective study was undertaken to evaluate the efficacy and safety of RFA as a treatment modality for PTC metastatic to cervical lymph nodes in adult patients in the United States performed in the private outpatient endocrinology practice setting.

Table 1. International studies reporting radiofrequency ablation used in cervical metastases from papillary thyroid carcinoma
First author, year, country	N/n	%VR	%Efficacy	Follow-up (m)	Complications^a
Chung, 2021, S. Korea	119/172	81.2	72.1	47.9	21.4%
Chung, 2019, S. Korea	29/46	99.5	91.3	80	10.3%
Guang, 2017, China	33/54	94.9	61.1	21	NR
Kim, 2016, S. Korea	129	NR	NR	NR	10.1%
Kim, 2015, S. Korea	27/36	NR	86.1	36	7.3%
Lim, 2015, S. Korea	39/61	95.1	82	26.4	7.7%
Long, 2015, China	12/12	NR	NR	6	NR
Lee, 2014, S. Korea	32/35	96.4	88.6	30	17%
Wang, 2014, China	8/20	76.9	25	9.4	0%
Guenette, 2013, Ireland	14/21	NR	NR	61.3	7.1%
Park, 2011, S. Korea	11/16	50.9	NR	6	9%
Baek, 2011, S. Korea	10/12	93	50	23	10%

Abbreviations: %VR, percentage volume reduction; %Efficacy, the percentage of nodes that completely disappeared after radiofrequency ablation; m, months; N, number of patients; n, number of nodes; NR, not reported.
^aComplications, major and minor, as defined by the Society of Interventional Radiology criteria.

Table 2. Characteristics and baseline clinical features of patients included in the study
Patients (age/sex)	TNM	ATA/MACIS	Time (y)	Location	Num	Surg	RAI	Sys	Reason
Pt 1 (35/F)	T1b,N1a,M0	L/<4	2.5	L level VI	2	1	N	N	NSC: prior RLN injury
Pt 2 (43/M)	T1a,N1a,M0	I/<4	12	C level VI	2	4	Y	N	NSC: high risk
Pt 3 (44/F)	T3,Nx,M1	H/>4	4.3	L thyroid bed	1	1	Y	Y	Palliative
Pt 4 (51/M)	T2,N1a,M0	I/<4	9.5	R level VI	2	2	Y	N	Pt preference
Pt 5 (33/M)	T2,N1b,M0	I/<4	2.1	L thyroid bed	1	1	Y	N	NSC: high risk
Pt 6 (37/F)	T1,N1a,M0	L/<4	2	L level IV	1	1	Y	N	Pt preference
Pt 7 (37/F)	T2,N1a,M0	I/>4	5.7	R level III	1	1	Y	N	Pt preference
Pt 8 (39/M)	NA	NA	10.6	L level III	1	2	Y	N	Pt preference

Age is given in years.
Time refers to the time between the patients' initial thyroid surgery and the radiofrequency ablation procedure. Location refers to the surgical level of the neck the recurrence occurred. Reason refers to the reason patient underwent radiofrequency ablation rather than surgery.
MACIS score <4 indicates low-risk disease and >4 indicates higher risk disease.
Abbreviations: ATA, American Thyroid Association 2015 guidelines; C, central; F, female; H, high; I, intermediate; L, left; Lo, low; M, male; MACIS, distant metastasis, patient age, completeness of resection, local invasion, and tumor size; N, no; NA, not available; NSC, not a surgical candidate; Num, number: refers to the number of metastatic lymph nodes or lesions that were present; Pt, patient; R, right; RAI, radioactive iodine ablation; RLN, recurrent laryngeal nerve; Surg, surgeries: refers to the number of surgeries, including initial thyroidectomy the patient had prior to radiofrequency ablation; Sys, systemic therapies; TNM, tumor, node and metastases staging; Y, yes.

Table 3. Outcomes of cervical metastatic lymph nodes treated with radiofrequency ablation
Node	Pre-RFA vol (mL); d (cm); Tg (ng/mL)	Post-RFA vol (mL); d (cm); Tg (ng/mL)	E/V (J/mL)	Follow-up (days)	VR (%)	Response
1.1	0.417; 0.83; 0.7	0.014; 0.3; 0.4	1336	570	96.6	Near complete
1.2	0.183; 0.68; 0.7	0; 0; 0.4	1336	570	100	Complete
2.1	0.252; 1; 1.4	0; 0; 0.4	1367	494	100	Complete
2.2	0.132; 0.7; 1.4	0; 0; 0.4	1367	494	100	Complete
3.1	1.147; 1.4; 2	0.5; 0.6; 1.3	3979	467	56.3	Partial
4.1	0.232; 0.7; 0.8	0; 0; 1.3	4483	523	100	Complete
4.2	0.206; 0.8; 0.8	0; 0; 1.3	4483	523	100	Complete
5.1	1.247; 1.2; 15.2	0.15; 0.6; 0.2	2165	398	87.9	Partial
6.1	0.210; 1; 0.1	0; 0; 0.1	12 250	363	100	Complete
7.1	0.269; 0.38; <2	0; 0; <2	8333	438	100	Complete
8.1	0.148; 0.71; <0.4	0; 0; <0.4	30 405	162	100	Complete

Abbreviations: d, diameter: refers to the largest short-axis diameter of the lymph node/lesion; E/V, energy applied per unit volume; post-RFA vol, postradiofrequency ablation volume; pre-RFA vol, preradiofrequency ablation volume; Tg, thyroglobulin; VR, volume reduction.