Risk Factors for Esophageal Cancer in the Cohort of Nuclear Facility Workers

Purpose: To assess the influence of non-radiation factors and occupational radiation exposure on the incidence risk of esophageal cancer in nuclear workers considering various histological types of the cancer. Material and methods: The study was designed as a retrospective analysis that considered data on the cohort of workers employed at reactors, radiochemical and plutonium production facilities of the Mayak Production Association (PA) who had been hired during 1948–1982. The total number of workers included in the cohort was 21645. Using the EPICURE software, the relative risk (RR) and excess relative risk of the esophageal cancer incidence per unit of the accumulated gamma dose from external exposure (ERR/Gy) were estimated based on the Poisson regression. Results: By 31.12.2018, 47 esophageal cancers were reported in members of the study cohort; the majority of these cancers were squamous cell carcinomas. The incidence risk of esophageal cancer was lower in females than in males and it increased with attained age. The increased risk of esophageal cancer (all cases) was associated with current smoking (RR=12.6, 95 % CI 4.21, 42.13), gastroesophageal reflux disease (GERD) (RR=3.96, 95 % CI 1.60, 8.48), excess body weight and obesity (RR=1.21, 95 % CI 1.13, 2.08). The significantly increased RR of squamous cell esophageal carcinoma was found in current smokers and workers had GERD. The significantly increased RR of esophageal adenocarcinoma was found in current and former smokers. The risk of esophageal cancer (all cases and squamous cell carcinomas) was higher in workers who abused alcohol but the RR estimates were not statistically significant. A significant linear association of the esophageal cancer risk with gamma dose from external exposure was found: ERR/Gy=1.28 (95 % CI 0.21, 4.11) for all cases and ERR/Gy=1.01 (95 % CI 0.01, 3.95) for squamous cell carcinoma; these estimates are the risks adjusted for sex, age, smoking, alcohol, GERD and body mass index. No effect of occupational radiation exposure on the esophageal adenocarcinoma risk was found. Conclusion: This study confirmed obtained earlier data on the impact of occupational external gamma exposure on the risk of esophageal cancer in Mayak PA workers. The estimates of ERR/Gy of external gamma-ray exposure were updated having made adjustments for the most important non-radiation factors.