Recombinant Human Thyrotropin in Thyroid Remnant Ablation with 131-Iodine in High-Risk Patients

Abstract

Most patients with well-differentiated thyroid cancer (WDTC) are first treated by total thyroidectomy followed by remnant ablation (RA) with (131)I. There are less data regarding the efficacy of recombinant human thyrotropin (rhTSH) for patients with WDTC at high risk of relapse than for low-risk patients. This study compared the efficacies of rhTSH and thyroid hormone withdrawal (THW) to prepare patients at high risk of relapse for RA. Post-thyroidectomy patients with WDTC and complete tumor resection (n = 275) were studied. They were at high risk of recurrence (tumor size >4 cm and/or extrathyroidal extension [pT3] and/or lymph node metastases), and they did not have antithyroglobulin (Tg) antibodies. Group A (n = 77) received 0.9 mg rhTSH for 2 consecutive days followed by RA on day 3. The remaining 198 patients (group B) were prepared by THW for 4 weeks. Patients in groups A and B received 3.7 or 5.5 GBq (131)I. The groups were similar in terms of gender, age, histology, TNM (tumor-node-metastases) stage, (131)I activity, and frequency of metastases on post-therapy whole-body scanning (RxWBS). Among patients without metastases on RxWBS, RA was successful (stimulated Tg <1 ng/mL and negative diagnostic whole body scan and neck ultrasonography) in 56 of 70 patients in group A (80%) and in 135 of 169 patients in group B (79.9%). Among patients with Tg >1 ng/mL immediately before RA, the comparable success rates were 68.4% and 67.4%, respectively. Among patients with metastases on the first RxWBS, no uptake was observed on the RxWBS 1 year later in 5 of 7 patients in group A (71.4%) and in 17 of 29 patients in group B (58.6%). The rhTSH stimulated serum Tg was <1 ng/mL in 3 of 5 and in 12 of 17 patients with a second negative RxWBS in groups A and B, respectively. Persistent disease (stimulated Tg >1 ng/mL and RxWBS continuing to show ectopic uptake) occurred in 2 of 7 patients in group A (28.5%) and in 12 of 29 patients in group B (41.3%). rhTSH is as effective as THW for RA in patients with WDTC who are at a high risk of relapse.