Thyroid carcinoma after radioactive iodine therapy for Graves' disease

Although the causal relation between radioactive iodine therapy (RIT) for Graves' disease and the subsequent occurrence of thyroid carcinoma is not definite, surgeons may be faced with the treatment of such patients. We studied the clinicopathologic features of patients with thyroid carcinoma following RIT for Graves' disease. From January 1983 to December 1991, 11 patients with thyroid carcinoma occurring 1 year or more after RIT for Graves' disease underwent surgery at Ito Hospital. These 11 patients accounted for 0.51% of 2146 surgical cases of thyroid carcinoma and 0.17% of 6419 RIT cases of Graves' disease during the period. They were all women, and their mean ages at RIT and surgery were 44.3 and 51.4 years, respectively. The administered dose of RI was 222.1 MBq and the absorbed dose 45.3 Gy on average. Total thyroidectomy was performed in two patients, subtotal thyroidectomy in three, and lobectomy in six. Bilateral modified neck dissection (MND) was added in two patients, and ipsilateral MND in seven. Histology revealed 10 papillary and 1 follicular carcinoma. The mean diameter of the tumor was 18.5 mm. Intraglandular dissemination of the tumor was noted in only one case and solid growth pattern in two. Nodal metastasis was disclosed in six cases, but in five of them only one node was involved. The present study indicated that thyroid carcinoma occurring after RIT for Graves' disease is not an aggressive variety, and thyroid lobectomy with ipsilateral MND would be sufficient as surgical treatment for such patients.