Professor Jacob Adams, an associate professor in the Department of Community and Preventive Medicine at the University of Rochester Medical Centre and colleagues have indirectly evaluated the future thyroid cancer risks of modern patients by assessing the rates of thyroid cancer in a group that was treated with lower-dose chest radiotherapy in Rochester, NY, between 1953 and 1987. The group had been treated during infancy for an enlarged thymus, a condition that used to be thought to be a health problem. None of the radiation administered was for cancer, so the research was confounded by a susceptibility to the disease.

Adams re-surveyed the population between 2004 and 2008, and compared the health status of the group to their siblings who had not received radiation. Thyroid cancer occurred in 50 of the 1,303 irradiated patients compared to only 13 of the 1,768 siblings. The association between radiation and thyroid cancer remained strong even after researchers accounted for other factors that could contribute to thyroid cancer risk.

Radiation doses in the mid-century group overlapped with current medical practices; however, in general, higher doses and less precision were used years ago. Doses at the lower end of the study cohort were comparable to a diagnostic pediatric chest CT given today, the study said. Not surprisingly, researchers found that thyroid cancer risk increased with higher doses of radiation.

The data also might provide some insight about why the rates of thyroid cancer continue to rise, as the general public is increasingly exposed to higher doses of radiation through more frequently used imaging tests such as computed tomography.

Radiation Research 12/10

Top of page