Preleukemia following large dose radioiodide therapy for metastatic thyroid carcinoma

A 67-yr-old woman had follicular thyroid carcinoma metastatic to several osseous sites. There was also evidence of functioning pulmonary metastases. She was treated by total thyroidectomy and multiple doses of radioiodide (131I). Approximately 2.5 yr after the initial ablative dose, and a total dose of 820 mCi of sodium iodide 131I, preleukemic changes were noted in the bone marrow. This appears to be the second case of preleukemia that bears a temporal relationship to radioiodide therapy of thyroid carcinoma, and the first in which radioiodide alone has been used in therapy (without additional external radiation).