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Sept 16, 1968

Incidence of Leukemia Following Treatment of Hyperthyroidism: Preliminary Report of the Cooperative Thyrotoxicosis Therapy Follow-Up Study

JAMA. 1968;205(12):855-862. doi:10.1001/jama.1968.03140380059014

This study was conducted to test for an increase in the incidence of leukemia in hyperthyroid patients treated by radioactive iodine131I as compared to the incidence in patients treated differently. Of 36,000 patients from 26 medical centers, approximately 22,000 were treated with131I and about 14,000 were treated surgically or solely with antithyroid drugs. More than 96% of patients were followed up. Forty-four cases of leukemia occurred after, and 16 before, treatment. The incidence of leukemia in patients treated with131I for hyperthyroidism and the incidence in those treated surgically do not differ. Patients both undergoing surgery and receiving131I have a higher incidence of leukemia than any other treatment group. The observed mortality from leukemia for hyperthyroid patients is 50% higher than that of the US population.