Cancer incidence among the liquidators of the Chernobyl accident

The work presents data on incidence of solid malignant neoplasms among liquidators of the Chernobyl accident which have been gathered in Russian National Medical and Dosimetric Registry from 1986 to the beginning of 1996. RNMDR contains individual dosimetric data and results of annual medical check-ups of the liquidators living on the territory of Russia. The study involves male liquidators who had no oncological diseases before arrival to the 30-km zone and for whom the following information was available: confirmed dose of external irradiation, birth date, date of arrival to the 30-km zone, time spent in the 30-km zone, results of medical checkups. The number of liquidators under study was 114504 persons, which is about 68% of all liquidators registered in RNMDR. The average dose of the considered cohort is 108 mGy, the average age at the time of their first arrival to the 30-km zone is 34.3 year and the total number of person-years spent in the zone is 797781. The liquidators' cohort is briefly characterized, cancer incidence of liquidators is compared with that of the population of Russia as a whole by calculating standardized incidence ratio (SIR). SIRs with 95% confidence intervals for all solid malignant neoplasms and cancers of the digestive system were 1.23 (1.15; 1.31) and 1.11 (1.01; 1.24) respectively. Estimation of radiation risks for the same disease classes has revealed a statistically significant increase in cancer incidence with increase in external radiation dose of liquidators.