Endocrine Abstracts

Millions of people were exposed in 1986 to radioactive isotopes in fallout from the Chernobyl accident, with in the first 20 years a large increase in thyroid carcinoma incidence. There is a possible radiation related increase in breast cancer but as yet no general increase in malignancies.

The increase in thyroid carcinoma, attributable to the very large amounts of iodine 131 released, was first noticed in children, with a strong relationship between young age at exposure and risk of developing papillary thyroid carcinoma (PTC). The extent of the increase, the reasons for the relationship to age at exposure, the reduction in attributable fraction with increasing latency, and the role of environmental factors will be discussed.

The large number of radiation induced PTCs has allowed new observations. The subtype, molecular and clinical findings change with latency. The molecular findings will be considered; the gene rearrangements common in these radiation induced tumours are regarded as reflecting their aetiology. More information is needed on germline mutations conferring susceptibility to radiation induced PTCs, particularly DNA repair genes.

Current knowledge of radiation effects is largely dependent on evidence from exposure to atomic bomb whole body radiation, which led to increases in a wide range of malignancies including thyroid carcinomas. The radiation exposure to fallout after Chernobyl was very different from the whole body radiation after the atomic bombs. The type and molecular pathology of the thyroid tumors is predicted to continue changing with increasing latency, long latency tumors in other organs could occur in the future. A comprehensive follow up must continue for the lifetime of those exposed.