Effects of surgical method and TSH level before treatment on the efficacy and prognosis of ¹³¹I ablation residual thyroid in patients with differentiated thyroid cancer

Objective To analyze the effects of different surgical methods and thyroid stimulating hormone (TSH) levels before treatment on the efficacy and prognosis of ¹³¹I ablation residual thyroid in patients with differentiated thyroid cancer (DTC).

Methods The clinical data of 147 DTC patients received ¹³¹I ablation residual thyroid were retrospectively analyzed. The dose of ¹³¹I ablation was 3.7 GBq. The level of stimulated thyroglobulin (sTg) was measured, and the diagnostic whole body scan (Dx-WBS) was performed 6-9 months after treatment. According to the surgical methods, the patients were divided into bilateral total resection and cervical lymph node dissection (double total resection group), unilateral total resection and contralateral subtotal resection and cervical lymph node dissection (subtotal resection group), unilateral total resection and cervical lymph node dissection (unilateral total resection group). The patients were again divided into two groups with TSH=30 mU/L as the critical value. The two-sample χ² test was used to compare the success rate of ablation residual thyroid. LSD-t test was used to compare the TSH levels between groups received different surgical methods, and the optimal threshold was determined by receiver operating characteristic (ROC) curve.

Results Among 147 cases, 115 cases succeeded and 32 cases failed in residual thyroid ablation with a successful rate of 78.2% (115/147). There was no statistical significance in the effects of Gender, age, pathological type and TNM stage on the efficacy of ¹³¹I ablation (P > 0.05). The success rate of ¹³¹I ablation residual thyroid in the double total resection group (90.5%) was significantly higher than that in the subtotal resection group (69.2%) and unilateral total resection group (65.0%) (P < 0.01). The success rate of ¹³¹I ablation residual thyroid in patients with TSH≥30 mU/L (84.9%) was significantly higher than that in the TSH≥30 mU/L group (66.7%) (P < 0.01). The results of ROC curve showed that the optimal threshold of TSH before treatment to predict the success of ¹³¹I ablation residual thyroid was 102.0 mU/L. When sTg=1.71 μg/L at the first follow-up and 14.51 μg/L at the second follow-up, the sensitivity and specificity for predicting recurrence or metastasis were 82% and 80%, 94% and 80%, respectively.

Conclusions Bilateral total thyroidectomy with TSH > 102.0 mU/L before treatment can improve the success rate of ¹³¹I ablation residual thyroid, and the close follow-up of sTg after treatment can effectively predict recurrence or metastasis.