Recombinant human thyroid-stimulating hormone (rhTSH) in the radioablation of well-differentiated thyroid cancer: preliminary therapeutic experience

Abstract

Iodine-131 (I-131) ablation of thyroid remnant and/or persistent, recurrent or metastatic tumour is part of the initial and subsequent management of well-differentiated thyroid carcinoma. Key to optimizing the safety and efficacy of radioablation is maximizing the selective uptake of radioiodine by normal or neoplastic thyroid tissue. This is achieved by ensuring adequate serum concentrations of thyroid-stimulating hormone (TSH). Exogenous TSH administration obviates the thyroid hormone suppression therapy withdrawal that is necessary for endogenous TSH elevation. It also avoids the marked morbidity, discomfort, and impairment in professional and educational pursuits and quality of life that often result from such withdrawal. Multicentre clinical studies have documented the safety and efficacy of recombinant human TSH (rhTSH) in promoting radioiodine uptake in the diagnostic scanning of well-differentiated thyroid cancer. Study of the use of rhTSH to facilitate radioablation of remnant and malignant thyroid tissue is at an earlier stage, with formal clinical investigation underway. Since April 1995, however, rhTSH has been employed as a radioablative adjunct in over 100 patients in the manufacturer's Compassionate Use Program. Twelve of these cases, reported or reviewed in the present paper, provide preliminary evidence that rhTSH is safe and effective in the radioablation setting. More data are needed to confirm these observations and to provide guidelines for optimal radioiodine dosing, and should be furnished by ongoing clinical investigation. rhTSH is the only acceptable treatment option in a subgroup of patients with well-differentiated thyroid cancer, including those with hypopituitarism, ischaemic heart disease, a history of "myxoedema madness," debilitation due to very advanced disease or inability to produce TSH due to continued production of thyroxine by thyroid remnant or metastatic tumour. Therapeutic use of rhTSH may be considered in an increasing number of other cases.