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Early childhood exposure to radiation linked to thyroid cancer
Adams MJ. Radiat Res. 2010;174:753-762.
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Early childhood exposure to radiation from multiple CT scans or other radiotherapy increases the risk for thyroid cancer, according to a study conducted at the University of Rochester Medical Center.
Researchers collected health status data from a cohort of 1,303 patients who, as infants, had received lower-dose chest radiotherapy between 1926 and 1957 for treatment of an enlarged thymus. None of the patients were known to have cancer at the time. Researchers compared these results with the health status of the same group between 2004 and 2008. Health data on the non-irradiated siblings of these patients were also surveyed for the same years.
During 334,347 person-years of follow-up, thyroid cancer occurred in 50 of the irradiated patients (mean thyroid dose, 1.29 Gy) compared with 13 of the 1,768 non-irradiated siblings. The RR for thyroid cancer was 5.6 (95% CI, 3.1-10.8) when adjusted for attained age, Jewish religion, sex and history of goiter. The adjusted excess RR per gray was 3.2 (95% CI, 1.5-6.6); adjusted excess absolute risk per gray was 2.2 (95% CI, 1.4-3.2) per 10,000 person-years. Cumulative incidence of thyroid cancer was elevated in this cohort after a median 57.5-year follow-up and was dose-dependent.
Although researchers found that the incidence of thyroid cancer seemed to decrease after 40 years, they said survivors will continue to have an increased cumulative incidence of the disease.
“These results underscore the importance of limiting radiation doses in the youngest children whenever possible,” they wrote.
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