Impact of the Radiation Factor on Mean Survival Time for Chernobyl Clean-up Workers with Solid Cancer

The aim of this study was to investigate the mean survival time for Chernobyl clean-up workers (liquidators) with diagnosed solid cancer. The cohort of liquidators contained 142 871 males who worked in the Chernobyl exclusion zone from 1986–1987. Individual medical and dosimetry information collected during the follow-up period from 1991 up to 2015 was used in the study. The number of liquidators cases with documented stages of the disease was 7652, the number of overall death cases among those liquidators was 5085 (4351 deaths were due to cancer). Mean survival time for liquidators after the diagnosis of solid cancer (ICD-10: C00-C80.9) and documented tumor stages between 2000 over 2015 was 4.73 years. For tumors of respiratory organs (ICD-10: C30-C39.9), the mean survival time was 2.57 years; for tumors of digestive organs (ICD-10: C15-C26.9), 3.55 years. The mean survival time for liquidators with a documented diagnosis of cancer was continuously increasing despite the cohort aging and the increase of total mortality. The relationship between the mean survival time and tumor stage was studied. The dependence of the mean survival time on the stage of the tumor was investigated. The survival time, when changing from the 1st stage to the 4th stage, decreased seven times (from 8.62 to 1.22 years). The relationship between the mean survival time and radiation dose received by a liquidator was studied. Two dose groups were identified: group 0–100 mGy (average dose: 56.6 mGy) and group 100+ mGy (average dose: 187.9 mGy). Mean survival time was 4.66 and 4.72 years and the difference between the values was insignificant. Studies carried out in the cohort with varying size and age provided actual estimates of the effects of technological factors on health of certain human populations and groups.