Thyroid cancer after external or internal ionizing irradiation.

It has been known for 50 years that thyroid exposure to high doses of ionizing radiation in childhood and adolescence induces an appreciable cancer risk. Epidemiological studies in children treated with external radiotherapy for benign or malignant lesions in the head and neck have also shown the induction of thyroid cancer. The World Health Organization (WHO) has reported that the risk for developing thyroid cancer due to the Chernobyl accident is greatest in newborns and children below the age of 5, less in adolescents and negligible in adults. As reported, during the first 15 years after the accident, the increase in thyroid cancer cases in Belarus was 87.8 fold in children, 12.7 fold in adolescents and 4.5 fold in adults more than expected. Papillary thyroid cancer with a relative risk incidence of approximately 80% per se is typical in childhood and adolescence. We refer to the differences between adult and childhood papillary thyroid cancers. Gene mutations in thyroid tumors induced after Chernobyl accident have been studied extensively. The treatment comprises thyroid surgery, suppressive doses of thyroxine and radioiodine. It is noteworthy that the thyroid gland can be protected from the intake of radioactive iodine by oral administration of potassium iodide.