Efficacy and safety of ultrasound-guided radiofrequency ablation for low-risk papillary thyroid microcarcinoma in patients aged 55 years or older: a retrospective study

Figures & data

Figure 1. Follow chart of this study. PTC: papillary thyroid carcinoma; PTMC: papillary thyroid microcarcinoma; RFA: radiofrequency ablation.

Table 1. Demographics and characteristics of the nodules.

Characteristic	Patients (n = 95)
Patients (n = 95)
Age, years
Mean ± SD [range]	66 ± 4.4 [55, 74]
Gender (man/woman)	24/71
Man	24 (25.3%)
Woman	71 (74.7%)
Follow up (month)	36.6 ± 16.6 [15, 74]
PTMCs (n = 95)
Position 1
Isthmic	8 (8.4%)
Left lobe	45 (47.4%)
Right lobe	42 (44.2%)
Position 2
Uper	13 (14.8%)
Middle	49 (55.7%)
Lower	26 (27.4%)
Largest diameter, cm
Mean ± SD [range]	0.607 ± 0.196 [0.2, 1.0]
Initial tumor volume, mm^3
Mean ± SD [range]	107.27 ± 99.10 [6.29, 424.44]
Ratio of taller than wide
<1	46 (48.4%)
>1	49 (51.6%)
Edge
Smooth	32 (33.7%)
Ill-defined or irregular	63 (66.3%)
Calcification
No	43 (45.7%)
Dotted	42 (44.7%)
Scattered dots	8 (8.5%)
Large plaques	1 (1.1%)
CDFI (Adler)
0	65 (68.4%)
1	25 (26.3%)
2	5 (5.3%)
3	0
BRAF mutation
NO	17 (22.4%)
YES	59 (77.6%)
Thyroid function, mean ± SD [range]
T3	1.64 ± 0.27 [1.08, 2.49]
T4	101.86 ± 20.83 [71.2, 168.9]
FT3 level (pmol/l)	4.53 ± 0.51 [3.8, 6.64]
FT4 level (pmol/l)	14.82 ± 1.73 [10.95, 17.58]
TSH level (mIU/l)	2.05 ± 1.08 [0.5, 5.95]

SD: standard deviation; PTMC: papillary thyroid microcarcinoma; CDFI: color doppler flow imaging; T3: triiodothyronine; T4: thyroxine; FT3: free triiodothyronine; FT4: free thyroxine; TSH: thyroid-stimulating hormone.

Table 2. RFA information of the 95 nodules.

Radiofrequency ablation	Mean ± SD	Range
RFA power, Watt	4.89 ± 1.433	[3, 8]
RFA time, s	177.74 ± 128.091	[43, 767]
RFA energy, kJ/ml	0.749 ± 0.497	[0.17, 2.54]
Post-RFA volume, ml	1042.75 ± 752.24	[100.61, 4841.76]
Energy, /ml	0.849 ± 0.474	[0.274, 2.867]
Post-RFA volume/initial volume	16.745 ± 14.529	[0.864, 96.333]

RFA: radiofrequency ablation; SD: standard deviation.

Table 3. Complications after RFA.

Complication	Patient number	%	Time to recovery (days)
Hematoma	0	0
Fever	0	0
Pain	1	0.01	0.5
Neck swelling	0	0
Voice change	0	0
Wound infection	0	0
Cardiac event	1	0.01	1
Total events	2	0.02	0.75

RFA: radiofrequency ablation.

Figure 2. A 60-year old woman with a papillary thyroid carcinoma in the middle of the left thyroid lobe (A) A hypoechoic nodule (white arrow) with an irregular margin was detected in the middle of the left thyroid lobe. (B) Immediately after radiofrequency ablation (RFA), a non-enhanced area measuring 1.4 × 1.4 × 1.4 cm was observed in the ablation zone. (C–E) Follow-up images showed that the ablation zone decreased gradually to 1.1 × 1.1 × 0.8, 0.9 × 1.0 × 0.8, and 0.6 × 0.7 × 0.5 cm at 1, 3 and 6 months, respectively. (F) At 12 months after RFA, the ablation area had disappeared on ultrasonography.

Figure 3. Tumor disappearance time curve after ablation. 46.3% of tumors completely disappeared within 12 months during their follow-up period.

Table 4. Volume changes of the nodules in the 95 patients.

Time	Volume (mm^3)		p-Value (vs last volume)	VRR (%)
	Mean ± SD	Range		Mean ± SD	Range
Pre-ablation	107.27 ± 99.10	[6.29, 424.44]
Immediately after RFA	1042.75 ± 752.24	[100.61, 4841.76]	p < 0.01
1 month after RFA	484.36 ± 556.08	[0, 4401.60]	p < 0.01	−591.64 ± 623.65	[−3500.00, 100.0]
3 months after RFA	213.25 ± 318.80	[0, 2554.50]	p < 0.01	−170.89 ± 319.51	[−1677.78, 100.0]
6 months after RFA	84.41 ± 162.69	[0, 1383.36]	p < 0.01	9.74 ± 128.43	[−573.47, 100.0]
12 months after RFA	24.17 ± 69.81	[0, 603.65]	p < 0.01	77.99 ± 45.26	[−193.88, 100.0]
18 months after RFA	1.45 ± 10.70	[0, 88.00]	p > 0.01	99.35 ± 3.61	[77.78, 100.0]
24 months after RFA	0.89 ± 5.07	[0, 31.40]	p > 0.01	99.45 ± 3.05	[79.59, 100.0]
36 months after RFA	0.39 ± 2.79	[0, 23.60]	p > 0.01	99.78 ± 1.54	[87.14, 100.0]

RFA: radiofrequency ablation; SD: standard deviation; VRR: volume reduction rate.