The study presents the updated data on the multiple myeloma (MM) incidence in Ukrainian cleanup workers after the Chornobyl accident and their survival. The epidemiological analysis is based on the extended follow-up period to identity new MM cases for higher statistical power and to collect additional data on the disease course and outcome for the survival analysis. The objective of the study was to analyze the MM incidence and survival in Chornobyl cleanup workers in 1996 - 2013 in comparison with the national MM statistical data. A study cohort consisted of 152,520 male cleanup workers resided in one of 6 regions of Ukraine or Kyiv city and registered in the Ukrainian State Chornobyl Registry (SChR). The Cohort Database was linked to the Ukrainian National Cancer Registry (NCR) Database to identify MM cases and to analyze MM incidence in 1996 - 2013. Standardized incidence ratios (SIR) for MM over the period 1996 - 2013 were calculated as compared to the general population of Ukraine. A 10-year lag period (when incident cases are not considered radiation-related) was applied. One-year and 5-year cause-specific survival of MM cases were calculated as percentage of those who were alive correspondingly for 1 or 5 years after diagnosis among overall diagnosed. By the moment, the 5-year survival rate either for the sub-period 2008 - 2013 or for the whole study period 1996 - 2013 cannot be determined. Vital status data were updated according to the recent SChR and NCR information. 75 MM cases diagnosed in 1986?2013 were identified in the studied cohort. 69 of them were included to the incidence analysis considering a 10-year lag period. While the incidence over 15 years after the accident did not differ significantly from the corresponding rate in general population of Ukraine, a tendency to increase was seen in the period from 16 to 21 years after the accident, and significantly increased SIR estimate was revealed for 2008 - 2013 (SIR 1.86, 95 % confidence interval (Cl) 1.27 - 2.44). The highest incidence was detected in 2008 - 2013 among cohort members diagnosed over the age of 50 years mostly due to the significant excess among those aged 60 - 69 (SIR 2.46, 95 % Cl 1.32 - 3.59). Survival rates in cleanup workers were shown to be higher than in the general population of Ukraine (73.9 % and up to 65.0 %, respectively). Conclusions: SIR for the 2008 - 2013 period, 22 - 27 years after the accident, demonstrated the significant excess of MM incidence among male cleanup workers. Survival of MM cases is higher in cleanup workers in comparison with that in general population. This article is a part of a Special Issue entitled "The Chornobyl Nuclear Accident: Thirty Years After".

To identify a contributive role of changes in gene regulation of apoptosis and telomere length at transcriptional and translational levels to the formation of radiation-induced effects in immune system. Study groups included 310 Chornobyl (Chornobyl) cleanup workers (dose of external exposure (360,82 +- 32,3) mSv; age 58,9 +- 0,6 (M +- SD) years) and control (n = 77; age (52,9 +- 0,64) (M +- SD) years). Expression of CD95, phosphatidylserine receptors, bcl2 and p53 proteins was studied by flow cytometry; the relative expression (RQ) of BAX, BIRC5, FASLG, MADD, MAPK14, TP53, TP53I3, TERT, TERF1, TERF2 genes was performed using 7900 HT Fast RT-PCR System and TagMan technology. Relative telomere length (RTL) was quantified by flow-FISH assay. Dose-dependent deregulation of apoptosis was shown at transcriptional level (TP53, TP53 I3, BAX, BIRC5, FASL genes) and translational level (bcl-2 and p53 proteins) with blocking entry to apoptosis, dose-dependent activation of anti-apoptotic proteins and TP53-mediated expression of genes-inhibitors of apoptosis. After exposure below 100 mSv a decrease in TERT gene RQ was associated with shortened telomeres, after exposure to doses over 500 mSv the TERT RQ and RTL increase were associated with imbalance in TERF1 and TERF2 genes expression. Conclusion: our study demonstrates a presence ofsubsequent changes in gene expression, regulatory proteins pres& entation, telomere length and distribution of cells by the stages of apoptosis in a late period after radiation exposure from low-dose range to doses over 500 mSv. Results of the study contribute to the basic concepts on the late biological effects in immune system.