Sudden hemorrhage in metastatic thyroid carcinoma of the brain during treatment with iodine-131

A patient with papillary--follicular carcinoma of the thyroid, with metastases to the lungs, skeleton, and brain was treated 5 weeks after thyroidectomy with 135 mCi of 131I. Although preliminary studies with 1 mCi had not shown any iodine uptake by the brain metastasis, this lesion showed intense concentration at the time of the larger therapeutic dose. Four days later, acute hemorrhage of the tumor occurred, requiring surgical removal. Although 131I therapy would seem an unlikely cause of acute necrosis and hemorrhage in these lesions, the association of therapeutic radioiodine and hemorrhage is interesting. Since recent reports suggest that brain metastasis may be somewhat more common than previously suspected, we suggest that brain imaging be included in the workup prior to radioiodine therapy of patients with advanced metastatic disease or neurologic symptoms.