Radiation risks of Russian liquidators of the Chernobyl accident for the period 1992-2017. Part I: solid cancer incidence

This paper presents the results of a study of the National Radiation and Epidemiological Registry (NRER) on the assessment of radiation risks of solid malignant neoplasms (MNs) incidence in a cohort of Russian participants in the liquidation of the consequences of the Chernobyl accident (liquidators) for the observation period 1992 2017. The cohort size - 69,440 people, the total number of person-years under observation - 1266272, the average age at the time of entry into the Chernobyl accident zone - 33.9 years, and the average dose of external gamma irradiation of the whole body accumulated over the period of the liquidator’s operation - 132.9 mGy. During this observation period, 6981 new cases of solid MNs were identified, determined by the interval of diagnosis codes, in accordance with ICD-10, from C00 to C80, including 1908 cases of MNs of the respiratory system (code interval of ICD-10: C33-C34) and 1574 cases of MNs of the digestive system (code intervals of ICD-10: C15-C16 and C18-C21). A statistically significant excess of the incidence of solid MNs was revealed in the cohort of liquidators compared with the incidence of the male population of Russia by 11%: standardized incidence ratio SIR=1.11, with a 95% confidence interval (CI) (1.09; 1.14). Statistically significant estimates of excess relative risk (ERR) per unit dose for all solid MNs (ERR/Gy=0.48, 95% CI) were obtained within the linear non-threshold (LNT) model of the dependence of the incidence on the radiation dose (0.15; 0.84), p=0.005), and, in particular, for MNs of the digestive system (ERR/Gy=0.76, 95% CI (0.06; 1.61), p=0.033). Nonparametric estimates of the relative radiation risk (RR) for all solid MNs, received in the dose intervals, are consistent with the radiation risk assessments for the LNT ERR model, taking into account 95% CI of these estimates. The obtained estimates of the radiation risk of the incidence of MNs of the digestive system, as well as estimates of the radiation risk of the incidence of solid MNs, confirm the need for further radiation epidemiological studies.