Cancer and Other Mortality Risks in a Cohort of U.S. Radiologic TechnologistsIn 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. During the past year, we completed a third comprehensive survey of cancer and other medical outcomes, calendar-specific employment factors (procedures performed and related protection practices), and cancer risk factors. Nearly 74,000 of 102,000 (72%) known living first or second survey responders participated in the third survey. We published our first semi-quantitative radiation risk assessment for breast cancer. Studies of breast cancer and genetic polymorphisms in several gene pathways (e.g. ATM, double strand break repair, base excision repair, apoptosis) were completed and manuscripts submitted. Venipuncture blood samples were collected from another 756 breast cancer cases identified on the third survey, and a pilot study of DNA fingerprick blood sample collection by mail was launched. Additionally, we completed development of the Version-3.5 dosimetry system. Corroboration of 152 lifetime dose estimates using individual FISH measurements gives us confidence to use the Version 3.5 dose estimates to conduct dose-response analyses and proceed with publication.Cancer Mortality in Russian Nuclear Workers Exposed to Plutonium and Protracted External RadiationA 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 greater than 0.001).
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