Rads, Ca Mortality: A-Bomb Survivors

Radiation effects on cancer mortality among atomic bomb survivors

Kazunori Kodama, Dale L. Preston, Donald A. Pierce, Yukiko Shimizu, Akihiko Suyama, Eiichi Tahara.

Radiation Effects Research Foundation, Hiroshima, Japan; Radiation Effects Research Foundation, Nagasaki, Japan.

In order to determine the late health effects of atomic-bomb radiation, Radiation Effects Research Foundation has been conducting mortality surveillance on a cohort (Life Span Study, or LSS, of 93,000 atomic bomb survivors and 27,000 non- exposed residents of Hiroshima and Nagasaki) since 1950.

Deaths are routinely identified through the family registry system and ascertainment is virtually complete. The present report summarizes the results of the analyses of cancer mortality in the LSS for the period 1950 to date.

As of 1998 slightly more than 50 % of the cohort members had died. About 22 % of the deaths are attributed to cancer, 73 % to other diseases and 5 % to external causes. The central findings of the LSS has been an increase in cancer risk.

Besides the increase in leukemia mortality associated with radiation exposure, increases in solid cancer mortality such as cancers of the lung and stomach have also been demonstrated.

Radiation- related leukemia started to occur 2 to 3 years after exposure, reached its peak within 6 to 8 years after the bombing, and has since declined steadily.

However, the story has been different for solid cancers. Radiation- related solid cancer excess began to appear at later years and continued to increase proportionally with the increase in mortality in the control group as it aged.

Relative to background rates, an increase of solid cancer mortality is larger for those exposed as children than those exposed as adults.

However, since a majority of those exposed as children are still alive and risk estimates for them are somewhat uncertain at this stage, it is essential to continue their follow-up for more detailed risk estimate.

Other issues include the shape of dose response which appeared to be linear and the presence of heterogeneity in site-specific excess solid cancer risk.

AACR Abstract Number: 6394, 2003

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