If children are exposed to head and neck radiation, whether it be due to cancer treatments or diagnostic CT scans, there is an increased risk of thyroid cancer for most of the child’s life. The risk of thyroid cancer was found to be elevated 58 years or more after the initial radiation exposure, according to researchers at the University of Rochester Medical Center.
The study is the first of its kind. Never before have a group of people been followed up for such a long period of time after irradiation. The study, published in Radiation Research, provides insight into why thyroid cancer continues to rise. The general population is being exposed to increasing levels of radiation through the more and more frequent use of diagnostic imaging that requires it.
Lead study author, Jacob Adams, M.D., said, “Ionizing radiation is a known carcinogen and, in fact, about 1 million CT scans are performed every year on children five years or younger.
"Although CTs and other imaging tests are an important diagnostic tool and radiotherapy is an important treatment modality for cancer, with everything comes a risk. Our study attempted to measure the very long-term impact on thyroid cancer from medical irradiation. Our findings strongly suggest that those individuals exposed to irradiation from multiple CT scans to the head, neck and chest during early childhood and individuals treated with radiotherapy to the upper body as children have a lifelong increased risk of thyroid cancer."
The children in the radiation group were originally given lower dose chest radiotherapy between 1953 and 1987. They had had an enlarged thymus, something that doctors used to think was a health problem (but it isn’t) and that was the reason for their treatment. None of the treatments were for cancer, so the children didn’t have a genetic susceptibility to it. They were compared with siblings who were not exposed to radiation.
Both groups were followed up again between 2004 and 2008 and it was discovered that thyroid cancer had occurred in 50 of the 1,303 irradiated patients and only 13 of the 1,768 siblings who were not exposed to radiation.