EUROMEDICA  Hanover 3-4  Juni 2010	Advanced methods of diagnosis, treatment and prophylactics
	European Academy of Natural Sciences, Hanover European Scientific Society, Hanover Berliner Medizinischen Gesellschaft, Berlin

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After the accident at the Chernobyl Nuclear Power Plant most of Bryansk Oblast was exposed to radioactive contamination. Iodine radionuclides were determinative factors for internal irradiation of the population living in the contaminated territories in April and May 1986. It is because of the very fact that priority was placed on the study of the patients’ thyroid state as a lot of radiogenic thyroid cancer incidences were reported.

143 thyroid cancer incidences were diagnosed in the territory of Bryansk Oblast in 1981–1985, including one case of thyroid cancer diagnosed in a nine-year-old girl in 1984. During this period, the thyroid cancer incidence rate fluctuated from 1.3 per 100,000 people in 1984 to 2.6 in 1991-1992.

From 1986 to 2008, 3547 thyroid cancer incidences were diagnosed in the territory of Bryansk Oblast. Between 1986 and 1991, the thyroid cancer incidence rate increased from 3.3 per 100,000 people to 5.4. Since 1992, the rate has been steadily rising (p<0.05) vs. the one across the Russian Federation. Moreover, these rates have been 3–4 times higher (p<0.001) than the figures observed across the Russian Federation every year since 2002. The all-Russia highest thyroid cancer incidence rate — which amounted to 6.3 — occurred in 2007.

The ratios of males to females living in Bryansk Oblast and diagnosed with thyroid cancer before and after the Chernobyl accident changed from 1:4 to 1:8. There were no regularities identified with regard to the ratio of males to females diagnosed with thyroid cancer before the Chernobyl accident vs. the one calculated after the accident.

Between 1981 to 1997, the ratio of papillary thyroid cancer incidences to follicular one diagnosed in Bryansk Oblast was, on average, 1:1. From 1998 to 2008, it amounted, on average, to 4:1. Therefore, we can state that thyroid cancer which was diagnosed in some patients in Bryansk Oblast after the Chernobyl accident is likely to be of radiogenic nature. The younger the person was at the time of the exposure, the higher the risk of this pathology development is.

Between 1986 to 1990, which is a five-year period after the Chernobyl accident, no child living in Bryansk Oblast was diagnosed with thyroid cancer. In 1991–2000, the thyroid cancer incidence rate fluctuated from 0.3 per 100,000 children in 1991 to 2.5 in 1994. The pediatric thyroid cancer incidence rate across the Russian Federation with regard to the same period ranged from 0.07 in 1991 to 0.2 in 1999. In subsequent years, sporadic cases of this disease were observed in children living in Bryansk Oblast.

The period between 1981 and 1991 is the time of occurrences of spontaneous cancer (taking into account the latency period of 5–6 years, i.e. from 1986 to 1991). The relative risk (RR) was about 1, which means that pediatric incidence rate in Bryansk Oblast was close to the rate observed across the whole country both among boys and girls.

In 1992, the RR increased and then remained relatively constant up to and including 1999 (p<0.05)

From 1993 to 1999, the incidence rate of thyroid cancer diagnosed in boys was higher (p<0.05) than the figures across the Russian Federation. The highest RR occurred in 1999 and amounted to 43.01 (with the 95% confidence interval (CI) = 13.93 – 100.21).

The incidence rate of thyroid cancer diagnosed in girls was higher (p<0.05) than the figures across the Russian Federation in the period from 1994–1997. The highest RR occurred in 1995 and amounted to 17.85 (with the 95% CI = 8.85 – 45).

The data obtained bear evidence that 70% of thyroid cancer incidences diagnosed in patients living in Bryansk Oblast are of radiogenic nature. This assumption should be confirmed with further statistics supported with dosimetric investigation of each thyroid cancer incidence to be held in accordance with the “incidence-control” epidemiological survey methodology.