Thyroid treatment and its possible influence on occurrence of malignant tumors after diagnostic 131I.

The extent to which thyroid surgery, thyroid hormone medication or other forms of thyroid therapy were applied after diagnostic administration of 131I has been determined in 871 patients of the 10 133 patients reported previously. The relevant information was obtained from questionnaires and from hospital records. Of the 871 patients at least 58 per cent had received no form of thyroid treatment and 33 per cent had had some form of treatment, while in 9 per cent no information could be obtained. The large difference between the number of malignant tumors observed in the 10 133 patients after exposure to 131I and the number expected from UNSCEAR's risk figures for radiation-induced thyroid carcinoma (47--124 cases) cannot be ascribed to the various forms of thyroid treatment given after the 131I administration.