Risk factors of liver malignancies in workers chronically exposed to ionizing radiation

Abstract

OBJECTIVE: To assess the impact of non-radiation factors and ionizing radiation on the incidence of liver malignant neoplasms in workers of a nuclear facility. METHODS: This was a retrospective study that considered a cohort of Mayak PA workers (22,377 individuals hired during 19481982 and followed up until 31.12.2018). The analysis included 60 malignant neoplasms of liver that were histologically confirmed. Hazard ratio (HR) and 95% confidence intervals (CI) were estimated in relation to factors under the study using Poissons regression. RESULTS: The risk of total liver malignancies increased with attained age and for individuals with chronic liver diseases HR=3,59 (95%CI 1,57; 7,21), chronic gallbladder and biliary tract diseases HR=1,83 (95%CI 1,07; 3,11), gallstone disease HR=2,45 (95%CI 1,15; 4,77). Viral hepatitis elevated the risk of hepatocellular carcinoma (HCC) HR=7,41 (95%CI 1,20; 24,63). Gallstone disease raised the risk of cholangiocarcinoma (CC) HR=14,69 (95%CI 3,05; 56,18). Risk of hemangiosarcoma (HAS) was increased in individuals with chronic liver diseases HR=7,52 (95%CI 1,68; 24,48), and with diseases of the gallbladder and biliary tract HR=6,01 (95%CI 1,86; 26,88). The risks of total liver malignancies and HAS were found to increase due to external exposure at gamma dose 0,5 Gy and internal exposure at alpha dose of plutonium 1,0 Gy. The risk of HCC increased with alpha dose 4,0 Gy and was not associated with external gamma-ray exposure. The risk of CC increased with gamma-ray exposure at doses 1,0 Gy and was not associated with alpha particle exposure. Among total liver malignancies, the number of HAS was high (26,7%) and among them 68,8% were observed at internal exposure alpha doses 4,0 Gy. CONCLUSIONS: Incidence of liver malignancies in Mayak PA workers was associated with ionizing radiation, chronic diseases of hepatobiliary tract and viral hepatitis (in case of HCC). To investigate the risk related to occupational radiation exposure, we need to perform a dose-response analysis that will consider non-radiation factors.