Mass survey of gastric cancer and leukemia in Miyagi Prefecture, Japan

A little more than 20,000 examinees of x-ray mass survey of gastric cancer and the controls were followed up from 1960 to 1977. Cumulative doses of x-rays were calculated for each examinee, and a collective dose in person-year-rads was constructed. Incidence of leukemia was ascertained from Miyagi Prefectural Cancer Registry. Seven cases of leukemia were found out of 242,689 person-year-rads in the irradiated population, and 9 cases out of 273,344 person-years in the controls. Incidence rate in the two groups was identical. Therefore, the risk of this mass survey was disproved.