Comparisons between Criteria for Successful Radioiodine Remnant Ablation in a cohort of Patients with Papillary Thyroid Carcinoma

Abstract

Objective Multiple criteria for successful radioiodine remnant ablation (RRA) under thyroid-stimulating hormone (TSH)-stimulation have been inconsistently employed, resulting in difficulties in efficacy comparison and iatrogenic hypothyroidism. Establishing an optimal standard for successful RRA is a priority. Methods Five existing criteria for successful RRA under endogenous TSH-stimulation were retrieved and then compared in a cohort of 51 patients with papillary thyroid cancer post RRA. Criterion A, a negative diagnostic ¹³¹I whole-body scan (DxWBS); Criterion B, a negative DxWBS and serum thyroglobulin (Tg) < 2 ng/mL, irrespective of anti-thyroglobulin antibody (TgAb) level; Criterion C, Tg < 2 ng/mL with TgAb ≤ 46 IU/mL; Criterion D, a negative DxWBS and Tg < 1ng/mL with TgAb ≤ 100 IU/mL or a negative DxWBS with TgAb > 100 IU/mL; Criterion E, a negative DxWBS and Tg ≤ 1 ng/mL with TgAb ≤ 46 IU/mL. Non-TSH-stimulated DxWBS was compared to TSH-stimulated DxWBS. Results Success rates of 98.0% (50/51), 78.4% (40/51), 78.0% (32/41), 64.7% (33/51) and 56.1% (23/41) were achieved regarding the criteria A, B, C, D, and E, respectively. The success rate of RRA by criterion A was significantly higher than those by other criteria. The similar success rates of RRA by criteria B and C were higher than that by criterion E. The success rate of RRA regarding non-TSH stimulated DxWBS was comparable to that of TSH-stimulated DxWBS, with a negative predictive value of 98.0%. Conclusions Compared with negative TSH-stimulated DxWBS criterion, the success rate of RRA decreases when the cut-off value of serum Tg is introduced. A negative non-TSH-stimulated DxWBS seems promising in predicting a successful RRA.