Salvage radiofrequency ablation followed by external beam radiotherapy for inoperable recurrent differentiated thyroid cancer

Figures & data

Table 1. Baseline patient characteristics.

Characteristic	N = 11 (%)
Age (years)
<55	3 (27.7%)
>55	8 (72.3%)
Sex (Male vs. female)	1:10
Number of lesions	14
Tumor histology
Papillary	10 (90.9%)
Follicular variant of papillary	1 (9.1%)
Pretreatment survey
PET-CT	10 (90.9%)
Contrast-enhanced head & neck and chest CT	11 (100%)
Metastatic status at the diagnosis of rDTC
No	6 (54.5%)
Yes	5 (46.4%)
Mean Tg level (ng/ml) ± SEM (range)
M0	27.13 ± 16.04 (0.2-79.2)
M1	133.26 ± 60.18 (10.6-279.0)
Follow-up, median (range)	33.7 (5.8–39.5)

Tg: thyroglobulin; M0: patients without distant metastases; M1: patients with distant metastases; SEM: standard error of the mean.

Table 2. Characteristics of lesions and treatment outcomes.

Number of lesions	14
Location
Thyroid surgical bed	5
Paratracheal LN	8
Lateral neck LN	1
Largest diameter of tumor (cm)
Mean ± SEM (range)	2.1 ± 0.3 (0.8-4.5)
Tumor volume (ml)
Mean ± SEM (range)	11.8 ± 5.9 (1.2-86.0)
2-year locoregional control (%)	100
2-year volume reduction ratio (%)
Mean ± SEM (range)	92.1 ± 5.1 (67.6-100)
2-year Tg reduction rate of M0 (%)
Mean ± SEM (range)	95.7 ± 0.49 (95.17-96.15)
2-year overall survival	90.9%
Interval from RFA to the nadir Tg (month)
Median (range)	5.4 (4.7–14)
Nadir Tg of M0 after treatment (ng/ml)
Mean ± SEM (range)	1.40 ± 0.81 (0.20–4.88)

LN: lymph nodes; Tg: thyroglobulin; M0: patients without distant metastases; SEM: standard error of the mean.

Figure 1. Change in tumor volume percentage before RFA and RT and at each follow-up.

Error bars represent the standard error of the mean; ***p ≤ 0.001

Figure 2. A 63-year-old man with recurrent thyroid cancer.

(a) contrast-enhanced CT before RFA and RT, showing one enhanced mass invading the tracheal wall and esophageal wall; (b) PET-CT before RFA and RT, showing increased FDG uptake in the paratracheal mass lesion (SUV max: 22.25); (c) contrast-enhanced CT 39 months after RFA and RT, showing that the recurrent tumor had almost completely disappeared; (d) PET-CT 6 months after RFA and RT, showing background FDG avidity with complete metabolic response in the left paratracheal region; CT, computed tomography; RFA, radiofrequency ablation; RT, radiotherapy; PET-CT, positron emission tomography and computed tomography; FDG: fludeoxyglucose F-18; SUV max, maximum standardized uptake value

Figure 3. The relationship between relative tumor volume and relative Tg in patients with localized recurrent disease and initial detectable Tg (Pearson correlation coefficient, 0.886; p < 0.001).

Figure 4. (A) OS and (B) locoregional PFS of eligible patients after salvage RFA and RT.

Table 3. Incidence of toxicity.

Toxicity	Grade 1	Grade 2	≥Grade 3
Acute
Xerostomia	0	0	0
Pharyngeal mucositis	7(63.6%)	4(36.4%)	0
Dermatitis	8(72.8%)	3(27.2%)	0
Dysphagia	7(63.6%)	4(36.4%)	0
Late
Xerostomia	0	0	0
Laryngeal edema	0	0	0
Dermatitis	0	0	0
Dysphagia	0	0	0

Data availability statement

Research data are available upon request to the corresponding authors.