Thyroid hormone replacement one day before (131)I therapy in patients with well-differentiated thyroid cancer.

Objective: The current study aimed to determine the efficacy of radioiodine-131 ((131)I) ablation therapy with thyroid hormone replacement one day before (131)I administration in patients with well-differentiated thyroid cancer (DTC).

Methods: This retrospective study included 29 patients who underwent (131)I therapies twice for DTC during 6-12 months. Since all the patients obviously had residual lesions by their serum thyroglobulin levels or their scintigrams at the first therapies, they underwent the second (131)I therapies without diagnostic scintigraphy after the first therapies. After confirming the sufficient elevation of TSH concentration, thyroid hormone replacement was resumed one day before (131)I administration (3.7-7.4GBq). The ablation rate of thyroid remnant at the first (131)I therapy was evaluated by comparing (131)I post-therapeutic images of the two treatments.

Results: Three patients were administrated thyroid hormone after (131)I therapy because of insufficient TSH concentration under thyroid hormone withdrawal. In the remaining 26 patients, 41 thyroid remnant accumulations were detected in all 26 patients at the first (131)I therapy. Based on the second (131)I post-therapeutic images, successful ablation was confirmed in 24 of 26 patients (92.3%) and 38 of 41 sites (92.7%), which was comparable with historically reported ablation rates.

Conclusion: Thyroid hormone replacement one day before (131)I therapy could provide a sufficiently high ablation rate in patients with DTC.