POCHIN has recently analyzed the incidence of leukemia in patients previously given I131 (an internal source of beta and gamma rays) for the therapy of hyperthyroidism.1 The data were collected by questionnaire from those clinics in Great Britain which used the isotope therapeutically. Information was included which had been assembled by others in several additional countries where I131 therapy is extensively employed.
Eighteen cases of leukemia in hyperthyroid patients previously treated with I131 were collected through May, 1960. Three cases were also recorded in which the onset of leukemia had preceded I131 therapy and which might erroneously have been considered to have followed I131 therapy had not a preliminary blood count been performed.
Pochin concluded, "The present evidence, while giving no support to the idea that leukemia is induced by the radioiodine treatment of thyrotoxicosis, neither excludes such induction nor sets any upper
Werner SC, Gittelsohn AM, Brill AB. Leukemia Following Radioiodine Therapy of Hyperthyroidism. JAMA. 1961;177(9):646-648. doi:10.1001/jama.1961.73040350013014a