Background

Researchers from the Radiation Epidemiology Branch, National Cancer Institute and the University of Minnesota, School of Public Health have followed a nationwide cohort of 146,022 radiologic technologists in the U.S. since 1982. This cohort is known as the U.S. Radiologic Technologists Study (USRT) and its goal is to evaluate cancer and other disease risks associated with protracted low-dose ionizing radiation exposure. The ubiquitous nature of exposure of the general population to low-dose radiation from occupational, medical, and environmental sources makes this an important public health concern.

The USRT cohort is the largest cohort of medical radiation workers studied to date and the only one with substantial numbers of women, extensive cancer and other serious diseases risk factor data, incident and fatal cancer and other disease outcomes, estimates of individual historical occupational radiation doses, personal medical radiation doses, and personal and residential solar ultraviolet (UV) radiation doses derived largely from four questionnaire surveys administered during 1983-2014, and biospecimens from breast and thyroid cancer cases and comparison subjects. This cohort is uniquely suited to address gaps in our scientific understanding of radiation risks according to dose-rate of exposure, that is, whether disease risks are similar for comparable cumulative radiation doses from a single or a few high-dose exposures (e.g. atomic bomb, radiotherapy) or from many small doses received over a protracted period that may be mitigated by DNA repair or other mechanisms (e.g. occupational exposures). The large proportion of women (73%) in the cohort enables studies of radiation-related cancer risks for the two most radiosensitive organs, breast and thyroid. The availability of biospecimens allows for identifying genetic main effects for breast and thyroid cancers, rapidly replicating novel genetic main effects identified by consortium colleagues, and identifying potentially radiosensitive genetic variants that may influence the risk of breast and other cancers. Finally, the nationwide cohort distribution, with widely varying solar UV exposures, affords a rare opportunity to assess risks for melanoma, non-melanoma skin cancer, and other cancers that may be associated with ultraviolet radiation.

The fourth survey was completed in 2014. Information was collected on new cancer and other disease outcomes, disease risk factors, and work history with nuclear medicine and diagnostic and interventional fluoroscopy procedures. The information collected will enable the study team to improve occupational, and ultraviolet radiation exposure estimates and further clarify the role of radiation and other factors on cancer and other disease risks.