The long-term hazards of the treatment of thyroid cancer with radioiodine.

Two-hundred and fifty-eight patients treated with high-activity 131I for thyroid cancer and on prolonged follow-up have been reviewed to determine long-term hazards and their relation to the radiation dose received. The expectation of life of those dying from causes other than cancer was slightly reduced in the female patients. A small, significant excess of deaths from cancer of the bladder and from leukaemia was found which, assuming that these were due to radiation, gave inferred risk-rates respectively of 0.4 and 4.9 deaths per 10(4) PYG (patient-year-grays) to the bladder wall and red marrow. Of 31 younger patients (eight male, 23 female), four of the marriages have been infertile. The fertile marriages produced a total of 44 live births. Considerable gonad irradiation (estimated 0.8-2.7 Gy) was compatible with apparently normal fertility. Despite the high level of irradiation of the salivary glands, no malignancies and only one adenoma was found. Impaired pulmonary function occurred in only one of the patients who had diffuse bilateral metastases. In this patient, tumour in the lung was persistent throughout, so that radiation was probably not alone responsible.