Cancer and Other Mortality Risks in a Cohort of U.S. Radiologic Technologists? In 1982, the Radiation Epidemiology Branch (REB), in collaboration with the University of Minnesota, initiated a nationwide cohort study of cancer incidence and mortality among 146,022 U. S. radiologic technologists. The cohort is 73% female, offering a rare opportunity to study effects of protracted low- to moderate-dose radiation exposure on breast and thyroid cancer, the two most sensitive organ sites for radiation carcinogenesis in women. Other cancer and non-cancer serious disease outcomes are also being evaluated in relation to protracted low-to-moderate dose exposures. Major findings since 2001 include: Mortality risks for breast cancer increased significantly with increasing number of years worked before 1950; mortality from cerebrovascular diseases increased significantly with earlier year first worked and with number of years worked before 1950; significantly elevated risks were found for incident cancers of the breast (female), thyroid, and melanoma compared to SEER and adjusted for non-response. Internal cohort analyses revealed significantly elevated incidence risks for breast cancer associated with working before 1940, melanoma and non-melanoma skin cancers related to working before 1950, modest elevated risk for non-chronic lymphocytic leukemia related to working >5 years before 1950, and a suggested elevated risk for thyroid cancer with working before 1960, while no associations were found for lung cancer. Mutational analysis of the ATM genes revealed that mutations in these genes are unlikely to account for a significant fraction of inherited breast cancer but a few low-frequency polymorphisms may increase breast cancer risk; kin-cohort analyses of breast cancer among first-degree relatives found a non-significant elevated risk associated with HER2 variant status of probands, significantly increased risks associated with XRCC1 194 and BRIP1 919 variants, and significantly reduced risks associated with APEX 148 and BRCA2 372 variants. During the past year, progress was made on historical dose reconstruction, which is being undertaken to provide estimates of annual and cumulative occupational badge doses (personal dose equivalent) for each technologist for each year worked from 1916 through 2005, as well as absorbed doses to organs and tissues including bone-marrow, female breast, thyroid, ovary, testes, lung and skin. The annual doses are defined as density distributions to account for uncertainties in the estimates. During the past year, a third follow-up survey was conducted, the genetic studies were expanded, and additional refinements were made to the dose assessment.? ? Cancer Mortality in Russian Nuclear Workers Exposed to Plutonium and Protracted External Radiation? A cohort of 26,000 Mayak nuclear facility workers (in the Russian Federation) is being studied because they comprise a unique occupational group for protracted exposure to external radiation at high doses and exposure to plutonium. Dose-response relationships for exposure to external radiation were demonstrated for mortality from leukemia; cancers of the lung, liver and bone (analyzed as a single category); and all solid cancers other than lung, bone and liver cancer. Patterns of risk by sex, age at exposure and time since exposure were generally similar to those observed in A-bomb survivors. Mortality analyses have also clearly demonstrated that internal exposure to plutonium results in excess risks for cancers of the lung, liver and bone cancers, the sites receiving the highest doses from plutonium. Recently conducted dose-response analyses of lung cancer mortality indicated significant associations for both internal dose to the lung from plutonium and external dose (p < 0.001).
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