[Long-term hematologic changes caused by radioiodine treatment of thyroid cancer. I. Peripheral blood changes].

In a retrospective study, the hematologic parameters of 296 patients treated with iodine-131 (average: 536 mCi) for carcinoma of the thyroid gland were evaluated with respect to the different doses applied. The average observation period was 65 months. The most frequent hematologic modification was thrombocytopenia which was found in 35%, followed by erythrocytopenia in 24% of cases. The normal concentration of leucocytes was decreased in 11% and increased in 23% of cases, however, the medium value calculated for all patients showed a decrease of leucocytes by 7%. Pancytopenias were found in 4.4% of cases. The most severe decreases were presented after high doses of radio-iodine (greater than or equal to 1000 mCi). Pancytopenia may be considered as one of the causes of the death of three patients.