Value of postoperative thyroglobulin and ultrasonography for the indication of ablation and 131I activity in patients with thyroid cancer and low risk of recurrence

摘要

Background: This study investigated the value of postoperative stimulated thyroglobulin (Tg) combined with neck ultrasonography for the prediction of the posttherapy whole-body scanning (RxWBS) and the efficacy of ablation with 30 mCi 131I in patients with thyroid cancer and low risk of recurrence to identify those who do not require ablation or only need a low 131I activity. Methods: A total of 237 consecutive patients with well-differentiated thyroid cancer and low risk of recurrence who were initially treated by total thyroidectomy followed by remnant ablation with 1.1 or 3.7 GBq (30 or 100 mCi) 131I were studied. Neck ultrasonography, Tg after levothyroxine withdrawal, and anti-Tg antibodies (TgAb) were obtained before, and RxWBS was performed 7 days after 131I administration. Patients with TgAb were excluded. Results: Postoperative ultrasonography revealed lymph node metastases in 5/237 (2%) patients. RxWBS showed ectopic uptake in 3/232 (1.3%) patients with negative ultrasonography. The negative predictive value of postoperative stimulated Tg 1 ng/mL (n = 132) or 10 ng/mL (n = 213) combined with negative ultrasonography was 100%. Among patients with detectable postoperative stimulated Tg 10 ng/mL and negative ultrasonography, 50 received 1.1 GBq 131I and 31 received 3.7 GBq. In the control assessment, stimulated Tg 1 ng/mL and neck ultrasonography without anomalies were achieved in 47/50 (94%) and in 29/31 patients (93.5%). All patients with stimulated Tg ≤1 ng/mL, negative TgAb, and normal ultrasonography before ablation continued to show the same results 8-12 months after initial therapy as expected, irrespective of the administration of 1.1 GBq (n = 82) or 3.7 GBq 131I (n = 50). Conclusions: Measurement of stimulated Tg combined with neck ultrasonography after total thyroidectomy may exclude the need for ablation in 56% of low-risk patients without TgAb (Tg 1 ng/mL) and permit the administration of an activity of 1.1 GBq 131I in another 34% with low Tg levels.