Leukemia incidence in the Russian cohort of Chernobyl emergency workers

Insights into the Molecular Mechanisms of Genetic Predisposition to Hematopoietic Malignancies: The Importance of Gene-Environment Interactions

SUMMARY

The recognition of host genetic factors underlying susceptibility to hematopoietic malignancies has increased greatly over the last decade. Historically, germline predisposition was thought to primarily affect the young. However, emerging data indicate that hematopoietic malignancies that develop in people of all ages across the human lifespan can derive from germline predisposing conditions and are not exclusively observed in younger individuals. The age at which hematopoietic malignancies manifest appears to correlate with distinct underlying biological pathways. Progression from having a deleterious germline variant to being diagnosed with overt malignancy involves complex, multistep gene-environment interactions with key external triggers, such as infection and inflammatory stimuli, driving clonal progression. Understanding the mechanisms by which predisposed clones transform under specific pressures may reveal strategies to better treat and even prevent hematopoietic malignancies from occurring.Recent unbiased genome-wide sequencing studies of children and adults with hematopoietic malignancies have revealed novel genes in which disease-causing variants are of germline origin. This paradigm shift is spearheaded by findings in myelodysplastic syndrome/acute myeloid leukemia (MDS/AML) as well as acute lymphoblastic leukemia, but it also encompasses other cancer types. Although not without challenges, the field of genetic cancer predisposition is advancing quickly, and a better understanding of the genetic basis of hematopoietic malignancies risk affects therapeutic decisions as well as genetic counseling and testing of at-risk family members.

Radiation exposure and leukaemia risk among cohorts of persons exposed to low and moderate doses of external ionising radiation in childhood

BACKGROUND

Many high-dose groups demonstrate increased leukaemia risks, with risk greatest following childhood exposure; risks at low/moderate doses are less clear.

METHODS

We conducted a pooled analysis of the major radiation-associated leukaemias (acute myeloid leukaemia (AML) with/without the inclusion of myelodysplastic syndrome (MDS), chronic myeloid leukaemia (CML), acute lymphoblastic leukaemia (ALL)) in ten childhood-exposed groups, including Japanese atomic bomb survivors, four therapeutically irradiated and five diagnostically exposed cohorts, a mixture of incidence and mortality data. Relative/absolute risk Poisson regression models were fitted.

RESULTS

Of 365 cases/deaths of leukaemias excluding chronic lymphocytic leukaemia, there were 272 AML/CML/ALL among 310,905 persons (7,641,362 person-years), with mean active bone marrow (ABM) dose of 0.11 Gy (range 0-5.95). We estimated significant (P < 0.005) linear excess relative risks/Gy (ERR/Gy) for: AML (n = 140) = 1.48 (95% CI 0.59-2.85), CML (n = 61) = 1.77 (95% CI 0.38-4.50), and ALL (n = 71) = 6.65 (95% CI 2.79-14.83). There is upward curvature in the dose response for ALL and AML over the full dose range, although at lower doses (<0.5 Gy) curvature for ALL is downwards.

DISCUSSION

We found increased ERR/Gy for all major types of radiation-associated leukaemia after childhood exposure to ABM doses that were predominantly (for 99%) <1 Gy, and consistent with our prior analysis focusing on <100 mGy.

Lithuanian cohort of Chernobyl cleanup workers: Cancer incidence follow-up 1986-2012

BACKGROUND

Cancer risks following radiation exposure in adulthood after Chernobyl are less studied compared to those after exposure in childhood. We aimed to evaluate cancer risk in the Lithuanian cohort of Chernobyl cleanup workers 26 years after their exposure in Chernobyl.

METHODS

Study population (6707 men) was followed for cancer incidence upon return from Chernobyl till the end of 2012 by linkage procedure with the Lithuanian Cancer Registry and for migration and death - with Central Population Registry. The site-specific cancer risk in the cohort was estimated by calculating the standardised incidence ratio (SIR) with 95 % confidence interval (CI).

RESULTS

A total of 596 cancer cases was observed in the cohort, against 584 expected (SIR 1.02; 95 % CI 0.94, 1.11). Only incidence of mouth and pharynx cancers was increased compared to the expected (SIR 1.41; 95 % CI 1.07, 1.86). Nevertheless, an increased risk of thyroid cancer was observed among cleanup workers who were younger than 30 years when entering the Chernobyl zone (SIR 2.90; 95 % CI 1.09, 7.72), whose radiation dose was above 100 milisievert (mSv) (SIR 3.13; 95 % CI 1.30, 7.52) and who had shorter duration of stay (SIR 2.30; 95 % CI 1.03, 5.13).

CONCLUSIONS

Our findings are consistent with those observed in other cohorts of workers, namely, the increased risk of cancer sites related to behavioural factors. The increased risk of thyroid cancer among cleanup workers who were younger than 30 years when entering Chernobyl and whose radiation dose was above 100 mSv cannot exclude the association with the radiation exposure in Chernobyl.

Crude incidence, age-specific incidence, and standardized incidence rates of leukemia in children under 14 years of age in Iran: an updated meta-analysis

BACKGROUND

Cancer is the second leading cause of death in children aged 0-14 years and leukemia is the most prevalent of them among children in the world and Iran. Estimating cancer incidence is a vital tool in epidemiology and subsequent cancer control programs. The aim is to evaluate the crude incidence, age-specific incidence and standardized incidence rates of leukemia in these children in Iran through a meta-analysis.

METHODS

This is a systematic review and meta-analysis between 1950 and 2019. We searched national (Iran Medex, Mag Iran and Scientific Information Database) and international (Google Scholar, PubMed, Science Direct, Scopus, and the Web of Sciences) databases for this purpose. The quality of articles was evaluated using the guidelines checklist for critically appraising studies of the incidence of a health problem. After the quality assessment the random effect meta-analysis was used to estimate the incidence rates in overall and based on sex.

RESULTS

A total of 382 articles were identified in the search phase and finally, 15 studies were included. The crude incidence rate in the total population using the Random effect model was estimated at 29.29 (CI %95, 25.74-32.84) per one million children aged 0-14 years. This rate was 34.72 (CI %95, 28.85-40.59) in boys and 24.89 (CI %95, 20.28-29.5) in girls. According to the results, three provinces of Fars (51.48), Golestan (40.86) and Qazvin (35.82) had the highest prevalence, respectively.

CONCLUSION

Given that the incidence of leukemia in boys is higher than in girls and it is more drastic in some Iranian provinces, further attention should be dedicated to risk factors in boys and high risk locations in Iran to help prevent of incidence of this disease.

Relationship between follow-up periods and the low-dose ranges with statistically significant radiation-induced risk of all solid cancers in the Russian cohort of Chernobyl emergency workers

Radiation-induced risks for all solid cancer incidence and mortality were studied in the cohort of Russian Chernobyl emergency workers. The cohort included 69,440 persons with documented individual radiation dose accrued over the time of working in the Chernobyl zone. The mean age at entry into the zone of recovery operations was 33.9 years and accumulated radiation dose was 132.9 mGy. A total of 6981 solid cancer incident cases and 4272 deaths occurred in this cohort from 1992 to 2017. Three follow-up periods were studied: 1992-2009, 1992-2013, and 1992-2017. For each follow-up period, the lowest dose range with statistically significant (p < 0.05) radiation-induced risk of all solid cancer incidence and mortality were obtained. For the incidence of all solid cancer during the follow-up period 1992-2009, this lowest dose range was estimated to be 0-250 mGy with an excess relative risk per dose of ERR Gy^-1 = 0.51 and 95% confidence interval (CI) (0.02; 1.05) Gy^-1. For the period 1992-2013, the lowest dose range was 0-175 mGy with ERR Gy^-1 = 0.85 (95% CI 0.03; 1.78), while for the whole follow-up period 1992-2017, it was 0-175 mGy with ERR Gy^-1 = 0.81 (95% CI 0.08; 1.62). For mortality from all solid cancers during the follow-up period 1992-2009, the lowest dose range with statistically significant radiation-induced risk was estimated to be 0-225 mGy with ERR Gy^-1 = 1.07 (95% CI 0.31; 0.97). For the period 1992-2013, the lowest dose range was 0-225 mGy with ERR Gy^-1 = 0.86 (95% CI 0.23; 1.58), while for the whole follow-up period 1992-2017, the lowest dose range was 0-200 mGy with ERR Gy^-1 = 0.82 (95% CI 0.10; 1.65). Thus, it was found that the minimal level of significant exposure (D_min), for which a statistically significant radiation-induced risk of all solid cancers was obtained for Russian emergency workers (with individual doses of 0 - D_min), decreases with increasing duration of cohort observation, both for cancer incidence and mortality.

Cancers after Chornobyl: From Epidemiology to Molecular Quantification

An overview and new data are presented from cancer studies of the most exposed groups of the population after the Chornobyl accident, performed at the National Research Center for Radiation Medicine (NRCRM). Incidence rates of solid cancers were analyzed for the 1990-2016 period in cleanup workers, evacuees, and the general population from the contaminated areas. In male cleanup workers, the significant increase in rates was demonstrated for cancers in total, leukemia, lymphoma, and thyroid cancer, as well as breast cancer rates were increased in females. Significantly elevated thyroid cancer incidence was identified in the male cleanup workers cohort (150,813) in 1986-2012 with an overall standardized incidence ratio (SIR) of 3.35 (95% CI: 2.91-3.80). A slight decrease in incidence rates was registered starting at 25 years after exposure. In total, 32 of 57 deaths in a group of cleanup workers with confirmed acute radiation syndrome (ARS) or not confirmed ARS (ARS NC) were due to blood malignancies or cancer. Molecular studies in cohort members included gene expression and polymorphism, FISH, relative telomere length, immunophenotype, micronuclei test, histone H2AX, and TORCH infections. Analysis of chronic lymphocytic leukemia (CLL) cases from the cohort showed more frequent mutations in telomere maintenance pathway genes as compared with unexposed CLL patients.

Recent Epidemiologic Studies and the Linear No-Threshold Model For Radiation Protection-Considerations Regarding NCRP Commentary 27

National Council on Radiation Protection and Measurements Commentary 27 examines recent epidemiologic data primarily from low-dose or low dose-rate studies of low linear-energy-transfer radiation and cancer to assess whether they support the linear no-threshold model as used in radiation protection. The commentary provides a critical review of low-dose or low dose-rate studies, most published within the last 10 y, that are applicable to current occupational, environmental, and medical radiation exposures. The strengths and weaknesses of the epidemiologic methods, dosimetry assessments, and statistical modeling of 29 epidemiologic studies of total solid cancer, leukemia, breast cancer, and thyroid cancer, as well as heritable effects and a few nonmalignant conditions, were evaluated. An appraisal of the degree to which the low-dose or low dose-rate studies supported a linear no-threshold model for radiation protection or on the contrary, demonstrated sufficient evidence that the linear no-threshold model is inappropriate for the purposes of radiation protection was also included. The review found that many, though not all, studies of solid cancer supported the continued use of the linear no-threshold model in radiation protection. Evaluations of the principal studies of leukemia and low-dose or low dose-rate radiation exposure also lent support for the linear no-threshold model as used in protection. Ischemic heart disease, a major type of cardiovascular disease, was examined briefly, but the results of recent studies were considered too weak or inconsistent to allow firm conclusions regarding support of the linear no-threshold model. It is acknowledged that the possible risks from very low doses of low linear-energy-transfer radiation are small and uncertain and that it may never be possible to prove or disprove the validity of the linear no-threshold assumption by epidemiologic means. Nonetheless, the preponderance of recent epidemiologic data on solid cancer is supportive of the continued use of the linear no-threshold model for the purposes of radiation protection. This conclusion is in accord with judgments by other national and international scientific committees, based on somewhat older data. Currently, no alternative dose-response relationship appears more pragmatic or prudent for radiation protection purposes than the linear no-threshold model.

Influence of diet and metabolism on hematopoietic stem cells and leukemia development following ionizing radiation exposure

PURPOSE

The review aims to discuss the prominence of dietary and metabolic regulators in maintaining hematopoietic stem cell (HSC) function, long-term self-renewal, and differentiation.

RESULTS

Most adult stem cells are preserved in a quiescent, nonmotile state in vivo which acts as a "protective state" for stem cells to reduce endogenous stress provoked by DNA replication and cellular respiration as well as exogenous environmental stress. The dynamic balance between quiescence, self-renewal and differentiation is critical for supporting a functional blood system throughout life of an organism. Stress-conditions, for example ionizing radiation exposure can trigger the blood forming HSCs to proliferate and migrate through extramedullary tissues to expand the number of HSCs and increase hematopoiesis. In addition, a wealth of investigation validated that deregulation of this balance plays a critical pathogenic role in various different hematopoietic diseases including the leukemia development.

CONCLUSION

The review summarizes the current knowledge on how alterations in dietary and metabolic factors could alter the risk of leukemia development following ionizing radiation exposure by inhibiting or even reversing the leukemic progression. Understanding the influence of diet, metabolism, and epigenetics on radiation-induced leukemogenesis may lead to the development of practical interventions to reduce the risk in exposed populations.

Epidemiology of Late Health Effects in Ukrainian Chornobyl Cleanup Workers

This article summarizes the results of 30 y of follow-up of cancer and noncancer effects in Ukrainian cleanup workers after the Chornobyl accident. The number of power plant employees and first responders with acute radiation syndrome under follow-up by the National Research Center for Radiation Medicine decreased from 179 in 1986-1991 to 105 in 2011-2015. Cancers and leukemia (19) and cardiovascular diseases (21) were the main causes of deaths among acute radiation syndrome survivors (54) during the postaccident period. Increased radiation risks of leukemia in the Ukrainian cohort of 110,645 cleanup workers exposed to low doses are comparable to those among survivors of the atomic bomb explosions in Japan in 1945. Additionally, an excess of chronic lymphocytic leukemia was demonstrated in the cleanup workers cohort for 26 y after the exposure. A significant excess of multiple myeloma incidence [standardized incidence rate (SIR) 1.61 %, 95% confidence interval (CI) 1.01-2.21], thyroid cancer (SIR 4.18, 95% CI 3.76-4.59), female breast cancer (SIR 1.57 CI 1.40-1.73), and all cancers combined (SIR 1.07; 95% CI 1.05-1.09) was registered. High prevalence was demonstrated for cardio- and cerebrovascular diseases and mental health changes. However, the reasons for the increases require further investigation. To monitor other possible late effects of radiation exposure in Chornobyl cleanup workers, analytical cohort and case-control studies need to include cardiovascular pathology, specifically types of potentially radiogenic cancers using a molecular epidemiology approach. Possible effects for further study include increased rates of thyroid, breast, and lung cancers and multiple myeloma; reduction of radiation risks of leukemia to population levels; and increased morbidity and mortality of cleanup workers from cardio- and cerebrovascular pathology.

Radiation-related occupational cancer and its recognition criteria in South Korea

Ionizing radiation is a well-known carcinogen, and is listed as one carcinogenic agent of occupational cancer. Given the increase in the number of workers exposed to radiation, as well as the increase in concern regarding occupational cancer, the number of radiation-related occupational cancer claims is expected to increase. Unlike exposure assessment of other carcinogenic agents in the workplace, such as asbestos and benzene, radiation exposure is usually assessed on an individual basis with personal dosimeters, which makes it feasible to assess whether a worker’s cancer occurrence is associated with their individual exposure. However, given the absence of a threshold dose for cancer initiation, it remains difficult to identify radiation exposure as the root cause of occupational cancer. Moreover, the association between cancer and radiation exposure in the workplace has not been clearly established due to a lack of scientific evidence. Therefore, criteria for the recognition of radiation-related occupational cancer should be carefully reviewed and updated with new scientific evidence and social consensus. The current criteria in Korea are valid in terms of eligible radiogenic cancer sites, adequate latent period, assessment of radiation exposure, and probability of causation. However, reducing uncertainty with respect to the determination of causation between exposure and cancer and developing more specific criteria that considers mixed exposure to radiation and other carcinogenic agents remains an important open question.

History of Disaster Epidemiology

Disaster epidemiology is not a new field, and the methods utilized to conduct disaster epidemiology studies are no different than the methods used in everyday applied public health research and investigations. The only difference is the circumstances under which the methods are employed. The challenges of conducting epidemiologic studies during a disaster are many—limited access to study sites and populations; access to reliable electricity, connectivity, and communication systems; and typically a short time frame in which to gather, analyze, and report data to decision-makers so that it can be utilized to prevent morbidity and mortality. However, many innovations have been developed by disaster epidemiologists to meet these challenges. Rapid needs assessments, innovative surveillance and tracking systems, and adapted epidemiologic study designs are some of the innovations that will be discussed in this chapter.

Gilbert W. Beebe Symposium on 30 Years after the Chernobyl Accident: Current and Future Studies on Radiation Health Effects

This commentary summarizes the presentations and discussions from the 2016 Gilbert W. Beebe symposium "30 years after the Chernobyl accident: Current and future studies on radiation health effects." The symposium was hosted by the National Academies of Sciences, Engineering, and Medicine (the National Academies). The symposium focused on the health consequences of the Chernobyl accident, looking retrospectively at what has been learned and prospectively at potential future discoveries using emerging 21st Century research methodologies.

Initial Diagnostic Workup of Acute Leukemia: Guideline From the College of American Pathologists and the American Society of Hematology

CONTEXT

- A complete diagnosis of acute leukemia requires knowledge of clinical information combined with morphologic evaluation, immunophenotyping and karyotype analysis, and often, molecular genetic testing. Although many aspects of the workup for acute leukemia are well accepted, few guidelines have addressed the different aspects of the diagnostic evaluation of samples from patients suspected to have acute leukemia.

OBJECTIVE

- To develop a guideline for treating physicians and pathologists involved in the diagnostic and prognostic evaluation of new acute leukemia samples, including acute lymphoblastic leukemia, acute myeloid leukemia, and acute leukemias of ambiguous lineage.

DESIGN

- The College of American Pathologists and the American Society of Hematology convened a panel of experts in hematology and hematopathology to develop recommendations. A systematic evidence review was conducted to address 6 key questions. Recommendations were derived from strength of evidence, feedback received during the public comment period, and expert panel consensus.

RESULTS

- Twenty-seven guideline statements were established, which ranged from recommendations on what clinical and laboratory information should be available as part of the diagnostic and prognostic evaluation of acute leukemia samples to what types of testing should be performed routinely, with recommendations on where such testing should be performed and how the results should be reported.

CONCLUSIONS

- The guideline provides a framework for the multiple steps, including laboratory testing, in the evaluation of acute leukemia samples. Some aspects of the guideline, especially molecular genetic testing in acute leukemia, are rapidly changing with new supportive literature, which will require on-going updates for the guideline to remain relevant.

Somatic health effects of Chernobyl: 30 years on

2016 marked the 30th anniversary of the Chernobyl Nuclear Power Plant accident. We and others wrote reviews for the 25th anniversary. Since then, additional papers have appeared and it seems timely to highlight lessons learned. To present, not a systematic review, but a commentary drawing attention to notable findings. We include not only recent reports and updates on previous results, but key findings from prior Chernobyl studies. The dose-dependent increase in Papillary Thyroid Cancer (PTC) following childhood I-131 exposure in Ukraine and Belarus has now been shown to persist for decades. Studies of post-Chernobyl PTCs have produced novel information on chromosomal rearrangements and gene fusions, critical to understanding molecular mechanisms. Studies of clean-up workers/liquidators suggest dose-related increases of thyroid cancer and hematological malignancies in adults. They also report increases in cardiovascular and cerebrovascular disease. If confirmed, these would have significant public health and radiation protection implications. The lens opacities following low to moderate doses found earlier are also a concern, particularly among interventional radiologists who may receive substantial lens doses. Finally, there is some, inconsistent, evidence for genetic effects among offspring of exposed persons. Further efforts, including improved dosimetry, collection of information on other risk factors, and continued follow-up/monitoring of established cohorts, could contribute importantly to further understand effects of low doses and dose-rates of radiation, particularly in young people, and ensure that appropriate public health and radiation protection systems are in place. This will require multinational collaborations and long-term funding.

Clinical characteristics of chronic lymphocytic leukemia occurring in chornobyl cleanup workers

The recently demonstrated radiation-induction of chronic lymphocytic leukemia (CLL) raises the question as to whether the amount of radiation exposure influences any of the clinical characteristics of the disease. We evaluated the relationship between bone marrow radiation doses and clinical characteristics and survival of 79 CLL cases diagnosed during 1986-2006 in a cohort of 110 645 male workers who participated in the cleanup work of the Chornobyl nuclear accident in Ukraine in 1986. All diagnoses were confirmed by an independent International Hematology Panel. Patients were followed up to the date of death or end of follow-up on 31 October 2010. The median age at diagnosis was 57 years. Median bone marrow dose was 22.6 milligray (mGy) and was not associated with time between exposure and clinical diagnosis of CLL (latent period), age, peripheral blood lymphocyte count or clinical stage of disease in univariate and multivariate analyses. Latent period was significantly shorter among those older at first exposure, smokers and those with higher frequency of visits to the doctor prior to diagnosis. A significant increase in the risk of death with increasing radiation dose was observed (p = 0.03, hazard ratio = 2.38, 95% confidence interval: 1.11,5.08 comparing those with doses ≥22 mGy to doses <22 mGy). After adjustment for radiation dose, survival of CLL cases was significantly shorter among those with younger age at first exposure, higher peripheral blood lymphocyte count, more advanced clinical stage of disease and older age at diagnosis (all p < 0.05). This is the first study to examine association between bone marrow radiation doses from the Chornobyl accident and clinical manifestations of the CLL in Chornobyl cleanup workers. The current study provides new evidence on the association of radiation dose and younger age at first radiation exposure at Chornobyl with shorter survival after diagnosis. Future studies are necessary with more cases in order to improve the statistical power of these analyses and to determine their significance. Copyright © 2016 John Wiley & Sons, Ltd.

A comparative assessment of major international disasters: the need for exposure assessment, systematic emergency preparedness, and lifetime health care

BACKGROUND

The disasters at Seveso, Three Mile Island, Bhopal, Chernobyl, the World Trade Center (WTC) and Fukushima had historic health and economic sequelae for large populations of workers, responders and community members.

METHODS

Comparative data from these events were collected to derive indications for future preparedness. Information from the primary sources and a literature review addressed: i) exposure assessment; ii) exposed populations; iii) health surveillance; iv) follow-up and research outputs; v) observed physical and mental health effects; vi) treatment and benefits; and vii) outreach activities.

RESULTS

Exposure assessment was conducted in Seveso, Chernobyl and Fukushima, although none benefited from a timely or systematic strategy, yielding immediate and sequential measurements after the disaster. Identification of exposed subjects was overall underestimated. Health surveillance, treatment and follow-up research were implemented in Seveso, Chernobyl, Fukushima, and at the WTC, mostly focusing on the workers and responders, and to a lesser extent on residents. Exposure-related physical and mental health consequences were identified, indicating the need for a long-term health care of the affected populations. Fukushima has generated the largest scientific output so far, followed by the WTCHP and Chernobyl. Benefits programs and active outreach figured prominently in only the WTC Health Program. The analysis of these programs yielded the following lessons: 1) Know who was there; 2) Have public health input to the disaster response; 3) Collect health and needs data rapidly; 4) Take care of the affected; 5) Emergency preparedness; 6) Data driven, needs assessment, advocacy.

CONCLUSIONS

Given the long-lasting health consequences of natural and man-made disasters, health surveillance and treatment programs are critical for management of health conditions, and emergency preparedness plans are needed to prevent or minimize the impact of future threats.

[Effects on health of the Chernobyl accident: 30 years on]

This paper reflects the current state of research into the short- and long-term effects on health in the former Soviet Union and Europe of the nuclear accident in Chernobyl. It discusses the latest results of epidemiological studies and presents future research perspectives.

Chronic Lymphocytic Leukemia in Chornobyl Cleanup Workers

This paper describes the chronic lymphocytic leukemia (CLL) incidence in a cohort of 110,645 (enlarged later to 152,520) male Ukrainian cleanup workers of the Chornobyl (Chernobyl) accident who were exposed to a range of radiation doses over the 1986-1990 time period. The standardized incidence rates are presented for a 27-y period after the exposure. For 2007-2012 period, the authors have identified the incident CLL cases in an enlarged cohort of 152,520 persons by linkage of the cohort file with the Ukrainian National Cancer Registry (NCRU). CLL data for the previous period (1987-2006) were identified in a frame of the Ukrainian-American leukemia study in the original cohort of 110,645 male clean-up workers. A significant CLL incidence excess was shown for the entire study period 1987-2012, with more prominent levels for the earliest years (1987-1996) when the standardized incidence rate (SIR) value was estimated to be 3.61 with 95% confidence interval from 2.32 to 4.91. In 2007-2012, the CLL incidence decreased substantially but still exceeded the national level although not significantly. In parallel, the several studies were performed at the National Research Center for Radiation Medicine (NRCRM) to explore if any clinical and cytogenetic features of CLL existed in the clean-up workers. The clinical study included 80 exposed and 70 unexposed CLL cases. Among the major clinical differences of the CLL course in the clean-up workers were a shorter period of white blood cells (WBC) doubling (10.7 vs. 18.0; p<0.001), frequent infectious episodes, lymphoadenopathy and hepatosplenomegaly (37 vs. 16), higher expression for CD38, and lower expression for ZAP-70 antigen.

30 years After the Chernobyl Nuclear Accident: Time for Reflection and Re-evaluation of Current Disaster Preparedness Plans

It has been 30 years since the worst accident in the history of the nuclear era occurred at the Chernobyl power plant in Ukraine close to densely populated urban areas. To date, epidemiological studies reported increased long-term risks of leukemia, cardiovascular diseases, and cataracts among cleanup workers and of thyroid cancer and non-malignant diseases in those exposed as children and adolescents. Mental health effects were the most significant public health consequence of the accident in the three most contaminated countries of Ukraine, Belarus, and the Russian Federation. Timely and clear communication with affected populations emerged as one of the main lessons in the aftermath of the Chernobyl nuclear accident.

EURADOS strategic research agenda: vision for dosimetry of ionising radiation

Since autumn 2012, the European Radiation Dosimetry Group (EURADOS) has been developing its Strategic Research Agenda (SRA), which is intended to contribute to the identification of future research needs in radiation dosimetry in Europe. The present article summarises-based on input from EURADOS Working Groups (WGs) and Voting Members-five visions in dosimetry and defines key issues in dosimetry research that are considered important for the next decades. The five visions include scientific developments required towards (a) updated fundamental dose concepts and quantities, (b) improved radiation risk estimates deduced from epidemiological cohorts, (c) efficient dose assessment for radiological emergencies, (d) integrated personalised dosimetry in medical applications and (e) improved radiation protection of workers and the public. The SRA of EURADOS will be used as a guideline for future activities of the EURADOS WGs. A detailed version of the SRA can be downloaded as a EURADOS report from the EURADOS website (www.eurados.org).

Non-radiation risk factors for leukemia: A case-control study among chornobyl cleanup workers in Ukraine

BACKGROUND

Occupational and environmental exposure to chemicals such as benzene has been linked to increased risk of leukemia. Cigarette smoking and alcohol consumption have also been found to affect leukemia risk. Previous analyses in a large cohort of Chornobyl clean-up workers in Ukraine found significant radiation-related increased risk for all leukemia types. We investigated the potential for additional effects of occupational and lifestyle factors on leukemia risk in this radiation-exposed cohort.

METHODS

In a case-control study of chronic lymphocytic and other leukemias among Chornobyl cleanup workers, we collected data on a range of non-radiation exposures. We evaluated these and other potential risk factors in analyses adjusting for estimated bone marrow radiation dose. We calculated Odds Ratios and 95% Confidence Intervals in relation to lifestyle factors and occupational hazards.

RESULTS

After adjusting for radiation, we found no clear association of leukemia risk with smoking or alcohol but identified a two-fold elevated risk for non-CLL leukemia with occupational exposure to petroleum (OR=2.28; 95% Confidence Interval 1.13, 6.79). Risks were particularly high for myeloid leukemias. No associations with risk factors other than radiation were found for chronic lymphocytic leukemia.

CONCLUSIONS

These data - the first from a working population in Ukraine - add to evidence from several previous reports of excess leukemia morbidity in groups exposed environmentally or occupationally to petroleum or its products.

Dosimetry Support of the Ukrainian-American Case-control Study of Leukemia and Related Disorders Among Chornobyl Cleanup Workers

This paper describes dose reconstruction for a joint Ukrainian-American case-control study of leukemia that was conducted in a cohort of 110,645 male Ukrainian cleanup workers of the Chornobyl (Chernobyl) accident who were exposed to various radiation doses over the 1986-1990 time period. Individual bone-marrow doses due to external irradiation along with respective uncertainty distributions were calculated for 1,000 study subjects using the RADRUE method, which employed personal cleanup history data collected in the course of an interview with the subject himself if he was alive or with two proxies if he was deceased. The central estimates of the bone-marrow dose distributions range from 3.7 × 10(-5) to 3,260 mGy, with an arithmetic mean of 92 mGy. The uncertainties in the individual stochastic dose estimates can be approximated by lognormal distributions; the average geometric standard deviation is 2.0.

Incidence and mortality of solid cancer among emergency workers of the Chernobyl accident: assessment of radiation risks for the follow-up period of 1992-2009

This paper presents the results of a retrospective cohort study of cancer incidence and mortality among emergency workers of the Chernobyl accident, for the follow-up period 1992-2009. The cohort selected for analysis consists of 67,568 emergency workers who worked in the Chernobyl exclusion zone in 1986-1987. External radiation whole-body absorbed dose varied from 0.0001 gray (Gy) to 1.24 Gy, with a median of 0.102 Gy. Over the follow-up period 1992-2009, a total of 4,002 solid cancers of different sites were identified as the result of annual compulsory health examination, and a total of 2,442 deaths from all solid cancers in the study cohort were reported. Poisson regression was applied for the analysis of cancer incidence and mortality. The analysis of the standardized incidence ratio (SIR) has shown a statistically significant increase in cancer incidence in the cohort as compared with baseline cancer incidence among males of Russia. The average excess over the entire follow-up period is 18 % [SIR = 1.18, 95 % confidence interval (CI) 1.15; 1.22]. In contrast, however, no increase in the mortality from all cancers among the emergency workers as compared to the baseline mortality in Russian men was found. Values of excess relative risk of cancer incidence and mortality per 1 Gy (ERR Gy(-1)) are 0.47 (95 % CI 0.03; 0.96, p value = 0.034) and 0.58 (95 % CI 0.002; 1.25, p value = 0.049), respectively. These values are statistically significant.

Estimating the lifetime risk of cancer associated with multiple CT scans

Multiple CT scans are often done on the same patient resulting in an increased risk of cancer. Prior publications have estimated risks on a population basis and often using an effective dose. Simply adding up the risks from single scans does not correctly account for the survival function. A methodology for estimating personal radiation risks attributed to multiple CT imaging using organ doses is presented in this article. The estimated magnitude of the attributable risk fraction for the possible development of radiation-induced cancer indicates the necessity for strong clinical justification when ordering multiple CT scans.

Comparing risk estimates following diagnostic CT radiation exposures employing different methodological approaches

The current study has two aims: the first is to quantify the difference between radiation risks estimated with the use of organ or effective doses, particularly when planning pediatric and adult computed tomography (CT) examinations. The second aim is to determine the method of calculating organ doses and cancer risk using dose-length product (DLP) for typical routine CT examinations. In both cases, the radiation-induced cancer risks from medical CT examinations were evaluated as a function of gender and age. Lifetime attributable risk values from CT scanning were estimated with the use of ICRP (Publication 103) risk models and Russian national medical statistics data. For populations under the age of 50 y, the risk estimates based on organ doses usually are 30% higher than estimates based on effective doses. In older populations, the difference can be up to a factor of 2.5. The typical distributions of organ doses were defined for Chest Routine, Abdominal Routine, and Head Routine examinations. The distributions of organ doses were dependent on the anatomical region of scanning. The most exposed organs/tissues were thyroid, breast, esophagus, and lungs in cases of Chest Routine examination; liver, stomach, colon, ovaries, and bladder in cases of Abdominal Routine examination; and brain for Head Routine examinations. The conversion factors for calculation of typical organ doses or tissues at risk using DLP were determined. Lifetime attributable risk of cancer estimated with organ doses calculated from DLP was compared with the risk estimated on the basis of organ doses measured with the use of silicon photodiode dosimeters. The estimated difference in LAR is less than 29%.

Leukaemia incidence in the Techa River Cohort: 1953-2007

Background:

Little is known about leukaemia risk following chronic radiation exposures at low dose rates. The Techa River Cohort of individuals residing in riverside villages between 1950 and 1961 when releases from the Mayak plutonium production complex contaminated the river allows quantification of leukaemia risks associated with chronic low-dose-rate internal and external exposures.

Methods:

Excess relative risk models described the dose–response relationship between radiation dose on the basis of updated dose estimates and the incidence of haematological malignancies ascertained between 1953 and 2007 among 28 223 cohort members, adjusted for attained age, sex, and other factors.

Results:

Almost half of the 72 leukaemia cases (excluding chronic lymphocytic leukaemia (CLL)) were estimated to be associated with radiation exposure. These data are consistent with a linear dose response with no evidence of modification. The excess relative risk estimate was 0.22 per 100 mGy. There was no evidence of significant dose effect for CLL or other haematopoietic malignancies.

Conclusion:

These analyses demonstrate that radiation exposures, similar to those received by populations exposed as a consequence of nuclear accidents, are associated with long-term dose-related increases in leukaemia risks. Using updated dose estimates, the leukaemia risk per unit dose is about half of that based on previous dosimetry.

Endothelial cells mitigate DNA damage and promote the regeneration of hematopoietic stem cells after radiation injury

Endothelial cells (ECs) are an essential component of the hematopoietic microenvironment, which maintains and regulates hematopoietic stem cells (HSCs). Although ECs can support the regeneration of otherwise lethally-irradiated HSCs, the mechanisms are not well understood. To further understand this phenomenon, we studied HSC regeneration from irradiated bone marrow using co-culture with human aortic ECs (HAECs). Co-culture with HAECs induced a 24-fold expansion of long-term HSCs (CD150(+), lineage(lo), Sca-1(+), c-Kit(+); CD150(+)LSK cells) in vitro. These cells gave rise to functional hematopoietic stem and progenitor cells (HSPCs) with colony-forming activity, multilineage reconstitution and serial transplantation potential. Furthermore, HAECs significantly reduced DNA damage in irradiated LSK cells within 24h. Remarkably, we were able to delay the exposure of irradiated bone marrow to the regenerative, HAEC-derived signals for up to 48h and still rescue functional HSCs. G-CSF is the gold standard for promoting hematopoietic regeneration in vivo. However, when compared to HAECs, in vitro G-CSF treatment promoted lineage differentiation and regenerated 5-fold fewer CD150(+)LSK cells. Together, our results show that HAECs are powerful, direct mitigators of HSC injury and DNA damage. Identification of the HAEC-derived factors that rescue HSCs may lead to improved therapies for hematopoietic regeneration after radiation injury.

Estimation of risk from medical radiation exposure based on effective and organ dose: how much difference is there?

The authors compare radiation risks of potential cancer following diagnostic radiation exposure evaluated with the use of organ and effective doses. Lifetime attributable risk values of CT scanning are estimated with the use of ICRP (Publication 103) risk models and Russian national medical statistics data. For populations under the age of 50, the risk evaluated using organ doses usually differs from that using effective doses by <30 %. In older populations, the difference can be up to a factor of 3. Calculated values of lifetime attributable cancer risk for particular organs are presented as well.

Chernobyl cleanup workers from Estonia: follow-up for cancer incidence and mortality

This study examined cancer incidence (1986-2008) and mortality (1986-2011) among the Estonian Chernobyl cleanup workers in comparison with the Estonian male population. The cohort of 4810 men was followed through nationwide population, mortality and cancer registries. Cancer and death risks were measured by standardised incidence ratio (SIR) and standardised mortality ratio (SMR), respectively. Poisson regression was used to analyse the effects of year of arrival, duration of stay and time since return on cancer and death risks. The SIR for all cancers was 1.06 with 95% confidence interval 0.93-1.20 (232 cases). Elevated risks were found for cancers of the pharynx, the oesophagus and the joint category of alcohol-related sites. No clear evidence of an increased risk of thyroid cancer, leukaemia or radiation-related cancer sites combined was apparent. The SMR for all causes of death was 1.02 with 95% confidence interval 0.96-1.08 (1018 deaths). Excess mortality was observed for mouth and pharynx cancer, alcohol-related cancer sites together and suicide. Duration of stay rather than year of arrival was associated with increased mortality. Twenty-six years of follow-up of this cohort indicates no definite health effects attributable to radiation, but the elevated suicide risk has persisted.