Exposure to ionizing radiation has been demonstrated to increase thyroid cancer risk over time. It is known that children’s exposure to radiation leads to a higher risk for thyroid cancer in adulthood. This is because children’s thyroid glands are more sensitive to radiation than adult thyroid glands. Previous studies showed an elevated risk for thyroid cancer in childhood cancer survivors. However, smaller radiation doses were previously also used for non-cancer disorders, such as treatment for fungal skin infections, thymus (a gland just below the thyroid) or tonsillar enlargement, and benign hemangiomas (non-cancerous growths of blood vessels under the skin) in infants and children. One of the studies included environmental radiation exposure, as the Japanese atomic bomb survivors were included.
This study was done to further characterize the risk of even small doses of radiation on developing thyroid cancer in children. In particular, this study was done to evaluate the dose-response pattern of radiation in children, to determine the role of chemotherapy drugs in this risk and to evaluate other factors such as age at exposure in risk for thyroid cancer.
THE FULL ARTICLE TITLE:
Veiga LH et al Thyroid Cancer after Childhood Exposure to External Radiation: An Updated Pooled Analysis of 12 Studies. Radiat Res. 2016;185(5):473-84. Epub April 29, 2016.
SUMMARY OF THE STUDY
Original data from 12 studies of people exposed to radiation at ages under 20 years old were used. These studies contained information about thyroid cancers that developed after treatment for other cancers. This expanded upon a previous report in 1995 of 7 studies with additional information and longer follow-up. The study used a complex statistical analysis to determine the risk of use of radiation. Age at exposure, calendar year of follow-up, time since exposure, age reached, exposure to chemotherapy drugs, thyroid radiation dose, and number of treatments were evaluated. They considered thyroid cancer cases as secondary if the patients had been treated with radiation for cancer, or primary if the patient had been treated with radiation for non-cancerous reasons.