Radioactive iodine treatment of metastatic thyroid carcinoma with clinical thyrotoxicosis

Differentiated thyroid cancer presenting with thyrotoxicosis due to functioning metastases

Thyrotoxicosis due to functioning metastases in differentiated thyroid cancer (DTC) is exceedingly rare. We report a case of follicular carcinoma in a 54-year-old manager, who presented with thyrotoxicosis, shortness of breath and lung metastases. Transbronchial biopsy of a pulmonary nodule demonstrated normal thyroid. This was interpreted as representing very well-differentiated thyroid cancer. CT, (131)I whole-body imaging and dosimetry is described following total thyroidectomy and repeated radioiodine administration (cumulative activity 34.6 GBq). The patient became asymptomatic with almost complete eradication of the pulmonary metastases. Potential complications of thyroid storm, bone marrow failure and pulmonary fibrosis following radioiodine are discussed, together with methods to minimise these risks.

Amiodarone-induced hyperthyroidism in a patient with functioning papillary carcinoma of the thyroid and extensive hepatic metastases

Thyroid hormone producing thyroid carcinoma is an uncommon cause of thyrotoxicosis. A patient with extensive hepatic metastases from well-differentiated carcinoma is presented. Administration of amiodarone for atrial fibrillation led to the development of hyperthyroidism. Precipitation of thyrotoxicosis by iodine-containing compounds in patients with thyroid carcinoma is rare. The relatively high iodine load and the slow elimination of amiodarone complicate the clinical management of such patients.

Iodine 131 (131I) as adjuvant therapy of differentiated thyroid cancer

The importance of the optimization of the up front management of DTC cannot be underestimated. An aggressive approach is advocated, except in situations widely accepted to be low risk (i.e., female patients <40 y, with tumors <1.0 cm confined to the gland). Distant tumor greatly reduces the chances for survival in all patients. The loss of iodine-concentrating ability removes systemic radioiodine from the therapeutic equation and thereby virtually eliminates chances for cure. The role of chemotherapy in non iodine responsive DTC is still in question, and a benefit in advanced disease has not been established. For non iodine-concentrating tumor that cannot be approached surgically, external beam therapy remains an option, both within the neck and for dominant foci of distant metastatic tumor (i.e., brain and bone). Any distant lesion demonstrating the capacity for radioiodine uptake also should be addressed with (131)1, because this will potentially treat tumor not evident on diagnostic survey. In conclusion, (131)1 has demonstrated efficacy for the postsurgical management of DTC. Although its acute and long-term side-effect profile is not especially worrisome relative to other forms of systemic cancer therapy, the administration of (131)1 is not entirely without risk. Taking into account many of the issues described in this article, the administration of (131)I should in every case be optimized. It also should be applied carefully and judiciously to patients expected to derive benefit.