Induction of leukemia by 131-I treatment of thyroid carcinoma

The records of 194 patients with thyroid carcinoma treated with (131)I, representing all cases thus treated in Denmark from 1948 to 1972, were reviewed. Two cases of myeloid leukaemia were found compared with 0·097 expected cases of non-lymphocytic leukaemia (0·05 > P > 0·01). In 5 series of (131)I treated thyroid carcinomata, 10 cases of myeloid leukaemia occurred in a total of 487 patients, corresponding to a frequency of leukaemia of about 2%. These findings appear to show that (131)I treatment of thyroid carcinoma is associated with a certain risk of development of leukaemia. This risk must be considered when treatment of localized thyroid carcinoma is planned.