Low versus high radioiodine activity for ablation of the thyroid remnant after thyroidectomy in Han Chinese with low-risk differentiated thyroid cancer

Figures & data

Table 1 Patient and tumor characteristics

Characteristics	Low-dose, n (%) (30 mCi, N=85)	High-dose, n (%) (100 mCi, N=88)	P-value
Age (years), mean ± SD (range)	45.33±14.69 (19–71)	47.89±14.82 (19–75)	0.792
Sex			0.499
Female	65 (76.47)	71 (80.68)
Male	20 (23.53)	17 (19.32)
Histology			0.775
Papillary	75 (88.24)	80 (90.91)
Follicular	8 (9.41)	7 (7.95)
Follicular variant	2 (2.35)	1 (1.14)
Family histology			0.134
Yes	3 (3.53)	8 (9.09)
No	82 (96.47)	80 (90.91)
TSH (μIU/mL), mean ± SD	42.15±5.81	41.83±5.63	0.71
Tumor diameter (cm)	1.69±0.84	1.98±0.99	0.034
Number of lobes affected			0.213
One	72 (84.71)	68 (77.27)
Both	13 (15.29)	20 (22.73)
Nodal metastasis			0.302
Present	5 (5.88)	11 (12.5)
Absent	47 (55.29)	43 (48.86)
Not rated	33 (38.82)	34 (38.64)
Tg level before ablation			0.392
⩽1 ng/mL	21 (24.71)	17 (19.32)
≥1 ng/mL	64 (75.29)	71 (80.68)
^131I uptake in neck (%)	1.50±0.86	2.04±0.91	0.139

Abbreviations: TSH, thyroid-stimulating hormone; Tg, thyroglobulin.

Figure 1 The images of WBS and thyroid static imaging of one successful ablation patient.

Notes: (A) A WBS 5 days after the procedure clearly demonstrates that after thyroidectomy the thyroid remnant has accumulated radioiodine in the neck (green arrow). (B) A WBS during follow-up shows that the accumulating spot in image A has been ablated by radioiodine and an abnormal accumulating spot was not found in other parts of the body. (C) Thyroid static imaging using ^99mTcO₄⁻shows the thyroid remnant after thyroidectomy in the neck area (green arrow). (D) Thyroid static imaging using ^99mTcO₄⁻ during follow-up shows no abnormal accumulating spot in the neck area. Scale for A and B: lateral axis: 170 cm; vertical axis: 60 cm. Scale for C and D: lateral axis: 20 cm; vertical axis: 25 cm.
Abbreviations: WBS, whole-body scan; ^99mTcO₄⁻ pertechnetate.

Table 2 Success and recurrence of ablation of the thyroid remnant using radioiodine

Study groups	First-ablation outcome		Second-ablation outcome		Final-ablation outcome		Recurrence
	Success	Failure	Success	Failure	Success	Failure
Low-dose, n (%)	66	19	15	4 (21%)	83	2 (2.4%)	0
(30 mCi, N=85)	(77.6%)	(22.4%)	(79%)		(97.6%)
High-dose, n (%)	63	25	22	3 (22%)	87	1 (1.1%)	0
(100 mCi, N=88)	(71.5%)	(28.5%)	(88%)		(98.9%)
P-value	0.36		0.416		0.54
Total	129/173 (74.6%)		37/44 (84.1%)		170/173 (98.3%)		0

Table 3 Common adverse effects related to radioiodine ablation

Adverse effects	Low-dose, N (%) (30 mCi, N=85)	High-dose, N (%) (100 mCi, N=88)	P-value
Nausea
1 week	10 (11.76)	25 (28.41)	0.006
1 month	2 (2.35)	8 (9.09)	0.058
3 months	1 (1.18)	3 (3.41)	0.329
Neck pain
1 week	14 (16.47)	30 (34.09)	0.008
1 month	10 (11.76)	13 (14.77)	0.56
3 months	5 (5.88)	9 (10.23)	0.295
Radiation gastritis
1 week	2 (2.35)	4 (4.55)	0.431
1 month	1 (1.18)	1 (1.14)	0.98
3 months	0 (0)	0 (0)
Radiation cystitis
1 week	1 (1.18)	2 (2.27)	0.581
1 month	0 (0)	0 (0)
3 months	0 (0)	0 (0)
Taste dysfunction
1 week	7 (8.24)	11 (12.5)	0.358
1 month	4 (4.71)	7 (7.95)	0.381
3 months	1 (1.18)	2 (2.27)	0.581
Salivary dysfunction
1 week	6 (7.06)	10 (11.36)	0.329
1 month	3 (3.53)	4 (4.55)	0.735
3 months	1 (1.18)	1 (1.14)	0.98
Sore throat
1 week	5 (5.88)	14 (15.91)	0.035
1 month	2 (2.35)	7 (7.95)	0.097
3 months	0 (0)	0 (0)
Dry eyes
1 week	6 (7.06)	9 (10.23)	0.459
1 month	5 (5.88)	4 (4.55)	0.692
3 months	3 (3.53)	3 (3.41)	0.966
Serious adverse events	0 (0)	1 (1.14)*

Note:

* Hyponatremia.