Breast cancer incidence in the regions of Belarus and Ukraine most contaminated by the Chernobyl accident: 1978-2016
Menée à partir de données des registres nationaux des cancers portant sur 85 132 patientes atteintes d'un cancer du sein, cette étude analyse l'association entre la dose de rayonnements ionisants absorbée par le sein et l'incidence de la maladie dans les régions les plus contaminées par l'accident de Chernobyl en Biélorussie et en Ukraine
Even 30 years after the accident, an association between breast cancer incidence and ionizing radiation exposure from Chernobyl fallout remains uncertain. We studied breast cancer incidence in the most contaminated regions of Belarus (Gomel and Mogilev) and Ukraine (Kyiv, Zhytomyr and Chernihiv) before (1978-1986) and after (1987-2016) the accident. Breast cancer cases and female population size data were received from the national cancer registries and the state departments of statistics. The study included 85 132 breast cancers with 150 million person-years at risk. We estimated annual rayon (district)-average absorbed doses to the breast from external and internal irradiation of the adult female population over the period of 1986-2016. We studied an association between rayon-average cumulative absorbed breast dose with 5-year lag, that is, excluding the exposure in 5 years prior to breast cancer diagnosis, and breast cancer incidence using negative binomial regression models. Mean (median) cumulative breast dose in 2016 was 12.3 (5.0) milligray [mGy] in Belarus and 5.7 (2.3) mGy in Ukraine, with the maximum dose of 55 mGy and 54 mGy, respectively. Breast cancer incidence rates statistically significantly increased with calendar year and attained age, and were higher in urban than in rural residents. Adjusting for time, age and urbanicity effects, we found no evidence of increasing incidence with rayon-average 5-year lagged cumulative breast dose. Due to ecological study design limitations, a case-control study covering this area with individually reconstructed absorbed breast doses is needed testing for association between low-dose protracted radiation exposure and breast cancer risk after Chernobyl.