Thyroid cancer after Chernobyl: mechanisms of overestimation

Abstract

Previously, we commented on some studies by A. Romanenko et al. (Jargin 2009), but this comment has not been referred to in subsequent publications by these authors. The main result of the recent study with participation of the same researchers (Fuzik et al. 2011) was the relatively higher increase in thyroid cancer (TC) incidence in areas more heavily contaminated by radionuclides as compared to the less contaminated ones. Considering previous discussions (Jaworowski 2010; Jargin 2011), this result could have been predicted in advance. The following should be commented in addition. The widely spread ‘‘Chernobyl victim syndrome’’ (Bay and Oughton 2005) impeded evaluation of the cause-effect relationship: some people used social competence and other tools to be registered as Chernobyl victims and confabulated information on their whereabouts during and after the accident. Many advanced cases found shortly after the Chernobyl accident and classified as radiogenic were obviously caused by the screening with detection of old neglected cancers, unrelated to the ionizing radiation, and by the fact that patients were brought from other areas and falsely registered as Chernobyl-related cases (Jargin 2010). Uneven geographical distribution of health care resources (Repacholi et al. 2002) obviously contributed to the unevenness of the registered TC incidence: its predominant increase was predictably found in contaminated areas better equipped with diagnostic facilities. It is obviously a reason explaining the differences in TC incidence between the more and the less contaminated areas found by Fuzik et al. (2011). Moreover, the capital city of Kiev, with better developed health care infrastructure, was counted among the more contaminated areas (Fuzik et al. 2011). Kiev together with the surrounding oblast (province) has a larger population than all other areas counted by Fuzik et al. (2011) as more heavily contaminated ones. The bias caused by obviously more developed health care facilities in the capital city and its surroundings is not commented on by the authors. Furthermore, there are medical institutions in Kiev servicing the whole country, and it is very probable that some patients, brought to the capital from other regions, were for certain reasons registered as locals or as Chernobyl victims. Motives for overestimation of Chernobyl consequences are well known: exaggeration of this topic facilitated financing; the Chernobyl accident has been exploited to strangle development of atomic energy (Jaworowski 2010). It partly explains, why in the high-exposure regions, thyroid cancer incidence rates were significantly higher (in some age groups) among people born in 1982–1986 (i.e., before the accident) compared to those born in 1987–1991 (Fuzik et al. 2011): at a later date after the accident, diagnostic quality was improved and cancerophobia subsided, eliminating prerequisites for overdiagnosis (Jargin 2010), and there were no motives to enhance the incidence figures in persons born after the accident. A concluding point is that overestimation of Chernobyl consequences can create a wrong concept about carcinogenicity of some radionuclides.