Relationship between follow-up periods and the low-dose ranges with statistically significant radiation-induced risk of all solid cancers in the Russian cohort of Chernobyl emergency workers.

Abstract

Radiation-induced risks for all solid cancer incidence and mortality were studied in the cohort of Russian Chernobyl emergency workers. The cohort included 69,440 persons with documented individual radiation dose accrued over the time of working in the Chernobyl zone. The mean age at entry into the zone of recovery operations was 33.9years and accumulated radiation dose was 132.9mGy. A total of 6981 solid cancer incident cases and 4272 deaths occurred in this cohort from 1992 to 2017. Three follow-up periods were studied: 1992-2009, 1992-2013, and 1992-2017. For each follow-up period, the lowest dose range with statistically significant (p < 0.05) radiation-induced risk of all solid cancer incidence and mortality were obtained. For the incidence of all solid cancer during the follow-up period 1992-2009, this lowest dose range was estimated to be 0-250mGy with an excess relative risk per dose of ERRGy-1 = 0.51 and 95% confidence interval (CI) (0.02; 1.05) Gy-1. For the period 1992-2013, the lowest dose range was 0-175mGy with ERRGy-1 = 0.85 (95% CI 0.03; 1.78), while for the whole follow-up period 1992-2017, it was 0-175mGy with ERRGy-1 = 0.81 (95% CI 0.08; 1.62). For mortality from all solid cancers during the follow-up period 1992-2009, the lowest dose range with statistically significant radiation-induced risk was estimated to be 0-225mGy with ERRGy-1 = 1.07 (95% CI 0.31; 0.97). For the period 1992-2013, the lowest dose range was 0-225mGy with ERRGy-1 = 0.86 (95% CI 0.23; 1.58), while for the whole follow-up period 1992-2017, the lowest dose range was 0-200mGy with ERRGy-1 = 0.82 (95% CI 0.10; 1.65). Thus, it was found that the minimal level of significant exposure (Dmin), for which a statistically significant radiation-induced risk of all solid cancers was obtained for Russian emergency workers (with individual doses of 0 - Dmin), decreases with increasing duration of cohort observation, both for cancer incidence and mortality.