RISK OF THYROID CANCERS FOLLOWING IRRADIATION

Evaluations of risks from radiation for use in radiological protection have been made recently by groups of experts set up by the International Commission on Radiological Protection, the International Atomic Energy Agency and the World Health Organisation and the United Nations Scientific Committee on the Effects of Atomic Radiation. The major disadvantage of the risk concept in radiological protection is due to the paucity of the data from which risk estimates can be made. This means that current risk estimates are very tentative and new data may lead to substantial changes. Such a situation has recently arisen as a result of a report published by Hempelmann and his colleagues. The data from this report have been analysed and a risk estimate for thyroid cancer has been obtained of 100/106/rad for persons who received X-irradiation to the thyroid as a result of treatment for thymic enlargement in infancy. This value of risk is compared with the previous lower estimates. A review is made of all the data available from which estimates of the risk of thyroid cancer can be calculated. The cancer risk following X-irradiation in adult life appears to be lower than that following X-irradiation in infancy. The finding of thyroid nodules in persons following intakes of radioiodine is discussed. It is noted that the life expectancy following diagnosis of thyroid cancer varies with the type of cancer and the age at diagnosis. Unlike most other cancers, the longest survival time appears to be for the youngest age groups. © 1968 Health Physics Society.