Chronic Myeloid Leukemia After Treatment with 131I for Thyroid Carcinoma

A 27-year-old male developed Philadelphia chromosome-positive chronic myeloid leukemia (CML) 13 years after a first dose of radioiodine (131I) therapy for papillary thyroid carcinoma. He had received a cumulative 131I dose of 670 mCi, in 8 divided doses over 8 years, up to April 1998, for ablation of 131I avid tissues over the anterior neck region. The leukemogenic potential of radioactive iodine has been pointed out by many authors, but most reported cases have been acute leukemias. A literature review disclosed only 9 cases similar to ours. At present, there is no evidence to prove whether the development of CML after thyroid carcinoma represents a treatment-induced complication, a coincidence, or an increased susceptibility to secondary malignancies due to the malignant process itself.