The study investigated an association between the germline polymorphism at TP53 codon 72 and the development of papillary thyroid cancer (PTC) following exposure to radiation from the Chernobyl accident. TP53 genotype was examined in 48 pediatric/adolescent (age at diagnosis <18 years) and 68 adult post-Chernobyl patient with PTC, 53 adult patients with sporadic PTC and 313 healthy individuals from Russian-Ukrainian population. In addition, we evaluated loss of heterozygosity for TP53 and the allele expression ratio. The genotype of the patients was correlated with clinicopathological data. Arg TP53 homozygotes were found to be significantly underrepresented among adults with post-Chernobyl PTC, but not in children and adolescents when compared with sporadic PTC cases and the general population. In the tumors, cell transformation did not lead to allelic loss or biased TP53 allele expression in heterozygous individuals. None of TP53 genotypes specifically associated with tumor stage and morphology, however there were particular correlations with lymph node status in certain age groups of radiation-associated cases not seen in sporadic PTCs. The findings suggest TP53 allele combinations other than Arg/Arg may contribute to the risk of development of PTC in individuals exposed to radiation during their late childhood, adolescence or in young adulthood.

An analysis is presented of solid cancer incidence during 11 years of follow-up (1991-2001) of Chernobyl emergency workers residing in Russia. The analysis is based on data from the cohort of male emergency workers from 6 regions in Russia including 55718 persons with documented external radiation doses in the range of 0.001-0.3 Gy who worked within the 30 -km zone in 1986-1987. The mean age at exposure for these persons was 34.8 years and the mean external radiation dose 0.13 Gy. In the cohort 1370 cases of solid cancer were diagnosed and 3 follow-up periods were considered: 1991-1995, 1996-2001 and 1991-2001. The second follow-up period was chosen to allow for a minimum latency period of 10 years being characteristic of solid cancers. For risk assessment two control groups have been introduced, the first 'external' one representing incidence rates for corresponding ages in Russia in general, the second 'internal' one consisting of emergency workers. The risk estimates were based on spontaneous incidence rates of solid cancer. The estimated standardized incidence ratio (SIR) is in good agreement (95% CI) with that of the control. The values of excess relative risk per unit dose (ERR/Gy) for solid malignant neoplasms have been estimated to be 0.33 (95% CI: -0.39, 1.22) (internal control) for the follow-up period 1991-2001 and 0.19 (95% CI: -0.66, 1.27) for 1996-2001.

This paper continues a series of publications that analyze the impact of radiation on incidence of circulatory system diseases in the cohort of Russian recovery operation workers (liquidators) and presents the results of the analysis of cardiovascular disease (CVD) incidence. The studied cohort consists of 53,772 liquidators who arrived in the Chernobyl accident zone within the first year after the accident (26 April 1986 to 26 April 1987). The individual doses varied from 0.0001 Gy to 1.42 Gy, and the mean external whole body dose in the cohort was 0.161 Gy. A total of 27,456 cases of CVD were diagnosed during the follow-up period 1986-2012 as a result of annual health examinations. A Poisson regression model was applied to estimate radiation risks and other risk factors associated with CVD. The following factors were identified as risk factors for CVD: the dose, duration of the liquidators' work in the Chernobyl zone, and concomitant diseases (diabetes mellitus, hypertension, overweight, and alcohol dependence). The baseline incidence of CVD is statistically significantly (p < 0.001) associated with all studied concomitant diseases. The incidence of CVD has revealed a statistically significant dose response with the lack of a latent period and with the average ERR Gy = 0.47, 95% CI = 0.31, 0.63, p < 0.001. Radiation risks of CVD statistically significantly (p = 0.01) varied with the duration of liquidators' stay in the Chernobyl zone; for those who stayed in the Chernobyl zone less than 6 wk, ERR/Gy = 0.80, 95% CI = 0.53; 1.08, p < 0.001.

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The work is concerned with assessment of radiation risks for non-cancer disease among the Chernobyl liquidators from 1986 to 1996. As of 1 January 1999, the Russian National Medical and Dosimetric Registry contains medical and dosimetric data for 174,000 liquidators. The cohort of 68,309 liquidators for whom best verified medical data are available is discussed. The dose dependency of incidence of non-cancer diseases was estimated by the cohort method and using the software package Epicure. For some classes of non-cancer diseases among liquidators, statistically significant estimates of radiation risk were derived for the first time. The highest excess relative risk per 1 Gy was found for cerebrovascular diseases; ERR Gy(-1)=1.17 at the 95% confidence interval (0.45; 1.88).

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In this study, we expanded on a previously published population-based case-control study on subjects exposed to iodine-131 (131I) from Chernobyl fallout at age ≤18 years using improved individual 131I absorbed thyroid doses. We further studied the impact of iodine deficiency and other selected host risk factors on 131I-related thyroid cancer risk after childhood exposure. We included 298 thyroid cancer cases and 1934 matched controls from the most contaminated regions of Belarus and the Russian Federation. We performed statistical analysis using conditional logistic regression models. We found a statistically significant linear quadratic dose-effect association between thyroid cancer and 131I thyroid dose in the range up to 5 grays (Gy). Self-reported personal history of benign nodules, any thyroid disease except thyroid cancer, family history of thyroid cancer, increased body mass index, and deficient stable iodine status at the time of the accident were statistically significant risk factors (p < 0.05 for each factor) for thyroid cancer after adjustment for thyroid 131I dose effect. Subjects who received stable iodine supplementation in the years after the accident had a significantly lower 131I-related risk of thyroid cancer. Our findings are important for thyroid cancer prevention, and for further improvement of medical surveillance in the affected populations.

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