Cancer Following Treatment of an Autonomously Functioning Thyroid Nodule With Sodium Iodide I 131

Three years, nine months after sodium iodide I 131 therapy for an autonomously functioning thyroid nodule (AFTN) the patient was discovered to have a multifocal thyroid carcinoma involving exclusively extranodular tissue. It is suggested that cancer was induced by a combination of low intensity radiation followed by endogenous thyroid stimulating hormone (TSH) stimulation (nodular function having been ablated). Because radiation to extranodular tissue is inevitable when AFTN are treated with sodium iodide I 131, it is suggested that surgery may be the preferable form of treatment. If surgery is refused or contraindicated patients with AFTN may be treated with sodium iodide I 131, but after therapy thyroid hormone should be administered orally to maintain suppression of endogenous TSH release, and regular examination of the thyroid gland should be carried out indefinitely.