Low-activity (2.0 GBq; 54 mCi) radioiodine post-surgical remnant ablation in thyroid cancer: comparison between hormone withdrawal and use of rhTSH in low-risk patients

Abstract

Objective: (a) To compare the efficacy of low-activity (2 GBq; 54 mCi) 131 I ablation using L-thyroxine withdrawal or rhTSH stimulation, and (b) to assess the influence of thyroid remnants volume on the ablation rate. Design: Patients underwent neck ultrasound, 131 I neck scintigraphy and radioiodine uptake. Posttherapy whole body scan (WBS) was acquired after 4-6 days. Ablation was assessed after 6-12 months by WBS, Tg and TgAb following L-thyroxine withdrawal. Methods: Group A: preparation by L-T 4 withdrawal (37 days); 21 patients received 131 I (2.02G 0.22 GBq; 54.6G5.9 mCi) and on the day of treatment, TSH, Tg, TgAb were measured; Group B: stimulation by rhTSH; 21 patients received 131 I (1.97G0.18 GBq; 53.2G4.9 mCi) 24 h after the second injection of rhTSH (0.9 mg) and TSH, Tg and TgAb were measured after 2 days. Results: At follow-up, 90.0% of patients from group A and 85.0% of patients from group B had Tg levels !1 ng/ml; no uptake was observed in 95.2% and in 90.5% of patients from group A or B respectively, with no statistical differences for both ablation criteria. Before 131 I treatment, small thyroid remnants (!1 ml) were detected by US in !25% of all patients. Conclusions: The use of rhTSH for the preparation of low-risk patients to ablation therapy with low activities of 131 I (2 GBq; 54 mCi) is safe and effective and avoids hypothyroidism. The presence of thyroid remnants smaller than 1 ml at US evaluation had no effect on the ablation rate.

University of the Philippines – Philippine General Hospital Revised Clinical Practice Guidelines for the Management of Well-Differentiated Thyroid Carcinoma of Follicular Cell Origin

“…Use of recombinant human TSH is probably the best solution to avoid hypothyroidism. Studies have found thyroid hormone withdrawal and rhTSH approaches to be equally effective in preparing patients for remnant ablation [55][56] or diagnostic examination. However, it is expensive and not readily available in our institution.…”

Recommendations of the Latin American Thyroid Society on diagnosis and management of differentiated thyroid cancer

“…However, recent publications have shown that 50 mCi 131 I is equally effective to 100 mCi 131 I for thyroid remnant ablation following rhTSH, with no interruption in L-T 4 administration (33,34). The use of rhTSH for ablation has shown to produce lesser exposure of radioiodine to the bone marrow and lowered toxicity related to the radioiodine dose than when administered after withdrawal (35,36).…”

Post-surgical thyroid ablation with low or high radioiodine activities results in similar outcomes in intermediate risk differentiated thyroid cancer patients

“…According to the American Thyroid Association (ATA) and European Thyroid Association (ETA) guidelines (1, 2), sufficient evidences have been accumulated indicating that in low-risk patients who are candidates for thyroid ablation, low RAI activities between 1100 and 1850 MBq have similar ablative effects (3,4,5,6,7,8,9,10,11) and similar (very low) recurrence rates during follow-up (12,13). Very recently, this concept has been reinforced by two prospective, randomized, multicenter studies (14,15), which compared the effectiveness of RAI ablation using 1110 or 3700 MBq of 131 I.…”