Scientific Protocol for the Study of Leukemia and Other Hematologic Diseases Among Clean-up Workers in Ukraine Following the Chernobyl Accident

Leukemia holds a special place in the study of radiation-related cancer because bone marrow is one of the tissues most sensitive to the carcinogenic effect of ionizing radiation, radiogenic leukemia has the shortest latent period among radiation-induced cancers, and its appearance suggests that solid tumors may follow. These same characteristics also contribute to its considerable significance in radiation protection. There are, nevertheless, important gaps in existing knowledge of radiation-induced leukemia, gaps that derive from characteristics of the study of the atomic bombing of Hiroshima and Nagasaki, and from studies of the effects of medical irradiation and studies of nuclear workers, these being the studies that have provided most of the information to date. These gaps include the presumed reduction in risk resulting from dose-fractionation and low dose-rate, and the time-response function in the first five years after exposure. The primary objective of this study is to investigate leukemia risk as a function of such radiation; it would constitute the largest epidemiologic study conducted to date among working-age males, a group of particular concern in establishing occupational radiation safety standards. In addition, data on cases of multiple myeloma and myelodysplasia identified in the cohort will be collected to test the hypothesis of a dose related association between radiation and increased risk for each of these diseases. The primary scientific objectives of the proposed study are to test the following hypotheses: (a) that there is a dose-related increase in risk of leukemia among these liquidators; (b) that the magnitude of any observed risk per unit dose is less than that seen in the atomic bomb survivors, exposed to essentially instantaneous radiation. Subsidiary objectives include: (a) to investigate the nature of the dose-response relationship among liquidators and to identify modifiers of risk, including time since exposure, age at exposure, etc.; (b) to test the hypothesis that there is a dose-related increased risk of multiple myeloma; (c) to test the hypothesis that there is a dose-related increased risk of myelodysplasial; (d) to collect and store buccal cells from about 2,000 liquidators with a wide range of dose estimates extending to well over 1 Gy for possible use in future molecular studies of their DNA.