The risk of developing cancer of the digestive organs (excluding intestines) in the South Urals Population Exposed to Radiation Cohort

Evaluation of the low dose effect on population health is still a relevant issue. It requires further studies to improve our understanding of these effects. To solve this problem, it is important to conduct studies of the late effects of radiation exposure with direct risk estimation in the population that combines all strata of the society: people of different sex, age, initial health status, social and economic status. Moreover, this population should be sizeable and has been followed up for a long-term period. This manuscript is the first to present the findings of the analysis of the incidence risk of cancer of all the digestive organs, excluding intestines, and stomach cancer taken separately in members of the Southern Urals Population Exposed to Radiation Cohort depending on the dose accumulated in the stomach over the period from 1956 through 2018. This cohort is comprised of individuals exposed in the Southern Urals in two radiation accidents (on the Techa River and in the East-Urals Radioactive Trace) over the period from 01.01.1950 through 31.12.1960. The cohort also includes those who were born during this period; they could have additional in utero exposure or have exposed parents. The population was affected by long-term combined exposure (external and internal) at the low-to-medium soft tissue dose range (up to 1.1 Gy). The size of the incidence cohort was 47,282 people. Over the follow-up period 01.01.1956-31.12.2018, the number of person-years made up 1 292 930; mean dose to the stomach was 47 mGy, maximum – 1,132 mGy. Excess relative risk of the cancer incidence of the digestive organs was assessed using the Poisson regression analysis. Calculations were performed using the EPICURE Statistical software package. Excess relative risk for stomach cancer with a 2-year minimal, was 0.98/Gy (р=0.026), for all cancers of the digestive organs, excluding intestines, – 0.58/Gy, р=0.06. There was no significant modification of the effect by non-radiation factors. These values of excess relative risk do not disagree with the results of similar studies in the Japanese cohort of the atomic bomb survivors who were compatible in terms of age but had acute exposure at higher doses. No significant dose dependence of the cancer incidence of the oral cavity, esophagus, liver, or pancreas was detected at this stage.