Cancer incidence risk of female reproductive organs in the Southern Urals Populations Exposed to Radiation Cohort: 1956-2019

Abstract

The objective of the study is to obtain direct estimates of the excess relative risk of the reproductive organ cancer in women from the cohort of the Southern Urals population exposed to radiation under chronic exposure in the dose range not exceeding 1 Gy. Materials and Methods: The analytical cohort of the Southern Urals population exposed to radiation of women included 26,076 individuals with a follow-up period of 65 years (1956 to 2019) and 749,053 person-years at risk. The cancer incidence catchment area is limited to five districts of the Chelyabinsk region, the city of Chelyabinsk and the city of Ozyorsk. Over a 65 year-period 601 cases of the reproductive organ cancers have been registered in the incidence catchment area. The average cumulative dose to the uterus for women in the analytical cohort was 42 mGy; the maximum dose was 988 mGy. A regression analysis with a simple parametric model of the excess relative risk was used in the study. The significance of the results was assessed by the maximum likelihood method with 95% probability. Calculations were performed with the statistical software package “Epicure”. Results: The risk analysis revealed a statistically significant linear dependence of the excess relative risk of the cervical cancer incidence and that of all reproductive organ cancers in total on the dose accumulated in the walls of the uterus. The paper assesses the influence of modifying factors available for analysis on the magnitude of the risk. No dependence of either uterine body cancer risk on the dose to the uterus or ovary cancer risk on the dose to the ovaries was revealed. The possibility of obtaining significant risk values of the development of site-specific cancers appeared with an increase in the size of the analyzed population as a result of combining people exposed in the Southern Urals in two radiation accidents into one cohort, which increased the statistical power of the study. Assessment of the excess relative risk of the reproductive organ cancer in this cohort was carried out for the first time. This cohort has a great potential for further research to obtain direct estimates of the radiation risk of cancer and non-cancer diseases due to chronic exposure in the dose range up to 1 Gy.