Radioiodine treatment of metastatic differentiated thyroid cancer in patients on L-thyroxine, using recombinant human TSH

Objective: This study tested the hypothesis that administration of human re combinant thyroid-stimulating hormone (rhTSH: Thyrogen, thyrotropin alpha) could promote iodine-131 (I-131) uptake in the therapy for metastatic or lo cally invasive differentiated thyroid cancer (DTC), obviating L-thyroxine s uppressive therapy (L-T4) withdrawal and hypothyroidism in patients with ad vanced disease. Methods: Twelve totally (or almost completely) thyroidectomized adults, nin e of whom had received earlier therapy after L-T4 withdrawal, underwent I t reatment while euthyroid on L-T4, after rhTSH administration. Nine underwen t diagnostic whole-body scanning (WBS) after two consecutive daily i.m. inj ections (0.9 mg) of rhTSH. They then received an identical second course of rhTSH to promote therapeutic 131(I) uptake. Post-therapy WBS was performed one week later Three patients received only rhTSH I-131 therapy. Results: Administration of rhTSH promoted I-131 uptake in all patients, as demonstrated by posttherapy WBS, Administration of rhTSH also promoted a si gnificant increase in serum thyroglobulin (Tg) concentrations, According to the most recent measurements, 3-12 months after therapy, serum Tg levels f ell in four, and stabilized in two out of eleven patients. Upon additional rhTSH-WBS 8 months post-study, a reduction in one metastatic site was noted in one patient. The rhTSH was well tolerated, with mild, transient fever a nd/or nausea occurring in only a minority of patients. Individuals with bon e metastases experienced degrees of peritumoral pain and swelling that were similar (though more short-lived) to those seen in the same or other patie nts after L-T4 withdrawal. Conclusions: Administration of rhTSH is a safe, successful tool for inducin g I-131 uptake in local and metastatic DTC lesions, and avoids L-T4 withdra wal, preserving metabolic homeostasis and preventing the debilitating effec ts of hypothyroidism.