The incidence of leukemia, lymphoma and multiple myeloma among atomic bomb survivors: 1950-2001

Risk bases can complement dose bases for implementing and optimising a radiological protection strategy in urgent and transition emergency phases

Current radiological emergency response recommendations have been provided by the International Commission on Radiological Protection and adopted by the International Atomic Energy Agency in comprehensive Safety Standards. These standards provide dose-based guidance for decision making (e.g., on sheltering or relocation) via generic criteria in terms of effective dose in the range from 20 mSv per year, during transition from emergency to existing exposure situation, to 100 mSv, acute or annual, in the urgent phase of a nuclear accident. The purpose of this paper was to examine how such dose reference levels directly translate into radiation-related risks of the main stochastic detrimental health effects (cancer). Methodologies, provided by the World Health Organization after the Fukushima accident, for calculating the lifetime and 20 year cancer risks and for attributing relevant organ doses from effective doses, have been applied here for this purpose with new software, designed to be available for use immediately after a nuclear accident. A new feature in this software is a comprehensive accounting for uncertainty via simulation technique, so that the risks may now be presented with realistic confidence intervals. The types of cancer risks considered here are time-integrated over lifetime and the first 20 years after exposure for all solid cancers and either the most radiation-sensitive types of cancer, i.e., leukaemia and female breast cancer, or the most radiation-relevant type of cancer occurring early in life, i.e., thyroid. It is demonstrated here how reference dose levels translate differently into specific cancer risk levels (with varying confidence interval sizes), depending on age at exposure, gender, time-frame at-risk and type of cancer considered. This demonstration applies German population data and considers external exposures. Further work is required to comprehensively extend this methodology to internal exposures that are likely to be important in the early stages of a nuclear accident. A discussion is provided here on the potential for such risk-based information to be used by decision makers, in the urgent and transition phases of nuclear emergencies, to identify protective measures (e.g., sheltering, evacuation) in a differential way (i.e., for particularly susceptible sub-groups of a population).

Time-Dependent Measurement of Nrf2-Regulated Antioxidant Response to Ionizing Radiation Toward Identifying Potential Protein Biomarkers for Acute Radiation Injury

PURPOSE

Potential acute exposure to ionizing radiation in nuclear or radiological accidents presents complex mass casualty scenarios that demand prompt triage and treatment decisions. Due to delayed symptoms and varied response of radiation victims, there is an urgent need to develop robust biomarkers to assess the extent of injuries in individuals.

EXPERIMENTAL DESIGN

The transcription factor Nrf2 is the master of redox homeostasis and there is transcriptional evidence of Nrf2-dependent antioxidant response activation upon radiation. The biomarker potential of Nrf2-dependent downstream target enzymes is investigated by measuring their response in bone marrow extracted from C57Bl/6 and C3H mice of both genders for up to 4 days following 6 Gy total body irradiation using targeted MS.

RESULTS

Overall, C57Bl/6 mice have a stronger proteomic response than C3H mice. In both strains, male mice have more occurrences of upregulation in antioxidant enzymes than female mice. For C57Bl/6 male mice, three proteins show elevated abundances after radiation exposure: catalase, superoxide dismutase 1, and heme oxygenase 1. Across both strains and genders, glutathione S-transferase Mu 1 is consistently decreased.

CONCLUSIONS AND CLINICAL RELEVANCE

This study provides the basis for future development of organ-specific protein biomarkers used in diagnostic blood test for radiation injury.

Acute and late effects of combined internal and external radiation exposures on the hematopoietic system

Purpose: Incidents, such as nuclear facility accidents and the release of a 'dirty bomb', might result in not only external irradiation of personnel, but additional internal exposures through concomitant inhalation and/or ingestion of radioactive particulates. The purpose of this study was to define the impact of such a combination of radiation injuries on the hematopoietic niche.Material and methods: To assess changes in the murine hematopoietic system, we used a combined exposure of total body irradiation (TBI, 6 Gy) followed immediately by an internal (intraperitoneal) administration of 100 µCi of soluble 137Cs. We then evaluated acute survival in combined versus single modality exposure groups, as well as assessing hematopoietic function at 12 and 26 week time points.Results: Acutely, the combination of external and internal exposures led to an unexpected delay in excretion of 137Cs, increasing the absorbed dose in the combined exposure group and leading to mortality from an acute hematopoietic syndrome. At 12 weeks, all exposure paradigms resulted in decreased numbers of phenotypic hematopoietic stem cells (HSCs), particularly the short-term HSCs (ST-HSC); long-term HSCs (LT-HSC) were depleted only in the internal and combined exposure groups. At 26 weeks, there was significant anemia in both the TBI alone and combined exposure groups. There were decreased numbers in both the LT- and ST-HSCs and decreased functionality, as measured by competitive repopulation, was seen in all radiation groups, with the greatest effects seen in the internal and combined exposure groups.Conclusions: Our data indicate that a combined injury of sublethal external irradiation with internal contamination induces significant and persistent changes in the hematopoietic system, as may have been predicted from the literature and our own group's findings. However, a novel observation was that the combined exposure led to an alteration in the excretion kinetics of the internal contamination, increasing the acute effects beyond those anticipated. As a result, we believe that a combined exposure poses a unique challenge to the medical community during both the acute and, possibly, delayed recovery stages.

Assessing Measurable Residual Disease in Chronic Myeloid Leukemia. BCR-ABL1 IS in the Avant-Garde of Molecular Hematology

Chronic myelogenous leukemia (CML) is a malignancy of the myeloid cell lineage characterized by a recurrent chromosomal abnormality: the Philadelphia chromosome, which results from the reciprocal translocation of the chromosomes 9 and 22. The Philadelphia chromosome contains a fusion gene called BCR-ABL1. The BCR-ABL1 codes for an aberrantly functioning tyrosine kinase that drives the malignant proliferation of the founding clone. The advent of tyrosine kinase inhibitors (TKI) represents a landmark in the treatment of CML, that has led to tremendous improvement in the remission and survival rates. Since the introduction of imatinib, the first TKI, several other TKI have been approved that further broadened the arsenal against CML. Patients treated with TKIs require sensitive monitoring of BCR-ABL1 transcripts with quantitative real-time polymerase chain reaction (qRT-PCT), which has become an essential part of managing patients with CML. In this review, we discuss the importance of the BCR-ABL1 assay, and we highlight the growing importance of BCR-ABL1 dynamics. We also introduce a mathematical correction for the BCR-ABL1 assay that could help homogenizing the use of the ABL1 as a control gene. Finally, we discuss the growing body of evidence concerning treatment-free remission. Along with the continuous improvement in the therapeutic arsenal against CML, the molecular monitoring of CML represents the avant-garde in the struggle to make CML a curable disease.

Analysis of 153 115 patients with hematological malignancies refines the spectrum of familial risk

Estimating familial cancer risks is clinically important in being able to discriminate between individuals in the population at differing risk for malignancy. To gain insight into the familial risk for the different hematological malignancies and their possible inter-relationship, we analyzed data on more than 16 million individuals from the Swedish Family-Cancer Database. After identifying 153 115 patients diagnosed with a primary hematological malignancy, we quantified familial relative risks (FRRs) by calculating standardized incident ratios (SIRs) in 391 131 of their first-degree relatives. The majority of hematological malignancies showed increased FRRs for the same tumor type, with the highest FRRs being observed for mixed cellularity Hodgkin lymphoma (SIR, 16.7), lymphoplasmacytic lymphoma (SIR, 15.8), and mantle cell lymphoma (SIR, 13.3). There was evidence for pleiotropic relationships; notably, chronic lymphocytic leukemia was associated with an elevated familial risk for other B-cell tumors and myeloproliferative neoplasms. Collectively, these data provide evidence for shared etiological factors for many hematological malignancies and provide information for identifying individuals at increased risk, as well as informing future gene discovery initiatives.

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.

Radiation Biology and Its Role in the Canadian Radiation Protection Framework

The linear no-threshold (linear-non-threshold) model is a dose-response model that has long served as the foundation of the international radiation protection framework, which includes the Canadian regulatory framework. Its purpose is to inform the choice of appropriate dose limits and subsequent as low as reasonably achievable requirements, social and economic factors taken into account. The linear no-threshold model assumes that the risk of developing cancer increases proportionately with increasing radiation dose. The linear no-threshold model has historically been applied by extrapolating the risk of cancer at high doses (>1,000 mSv) down to low doses in a linear manner. As the health effects of radiation exposure at low doses remain ambiguous, reducing uncertainties found in cancer risk dose-response models can be achieved through in vitro and animal-based studies. The purpose of this critical review is to analyze whether the linear no-threshold model is still applicable for use by modern nuclear regulators for radiation protection purposes, or if there is sufficient scientific evidence supporting an alternate model from which to derive regulatory dose limits.

Risk of Leukemia Associated with Protracted Low-Dose Radiation Exposure: Updated Results from the National Registry for Radiation Workers Study

While the link between risk of leukemia and acute radiation exposure is well established for large doses received acutely, uncertainty remains around the translation of these risk estimates to occupational exposure scenarios where the doses are low and accumulated over time, possibly over many years. We present leukemia incidence and mortality radiation risk estimates derived from the National Registry for Radiation Workers, which is a large cohort of occupationally exposed workers from the United Kingdom (UK). The cohort comprised 173,081 workers from the UK who were monitored for occupational exposure to radiation. The cohort was followed for a total of 5.3 million person-years and the incidence and mortality due to leukemia was identified through to the end of follow-up in 2011. Poisson regression was used to investigate the relationship between cumulative radiation dose and leukemia mortality and incidence rates using excess relative risk (ERR) and excess additive risk (EAR) models. The results of this work showed a collective dose of 4,414 person-Sv accumulated by the cohort with an average cumulative dose of 25.5 mSv. Among male workers both the ERR and EAR models showed evidence of increased leukemia risk (excluding chronic lymphatic leukemia) associated with increasing cumulative dose. The ERR was 1.38 per Sv (90% CI: 0.04; 3.24) and EAR was 1.33 per 10,000 person-year-Sv (90% CI: 0.04; 2.89) when a linear model was used. These excess risks were driven by increased risks for chronic myeloid leukemia [ERR/Sv = 6.77 (90% CI: 2.14; 15.44)]. In conclusion, this study provides further evidence that leukemia risks may be increased by low-dose and protracted external radiation exposure. The risks are generally consistent with those observed in the atomic bomb survivor studies, as well as with risk coefficients on which international radiation safety standards, including the dose limits and constraints used to control exposures, are based.

Three Synchronous Primary Extranodal Mantle Cell Lymphomas Involving Torus Tubarius, Posterior Nasopharynx, and Base of the Tongue 65 Years After Treatment of Chronic Sinusitis with Nasopharyngeal Radium Irradiation

Patient: Male, 81

Final Diagnosis: Mantle cell lymphoma

Symptoms: Dificulty in swallowing and pain in the right ear

Medication: —

Clinical Procedure: Otorhinolaryngology panendoscopy • biopsy of the tumors

Specialty: Otolaryngology

Demographic and Clinical Characteristics of Chronic Myeloid Leukemia Patients: A Study on Confined Populations of Southern India

Context: Chronic myeloid leukemia (CML) is one of the most common hematological malignancies in all populations throughout the world. Even though the pathophysiology of CML was well explained in majority of the studies, the incidence of CML was shown to exhibit population diversity, and hence, the demographic factors underlying CML origin remain to be understood. Further, the introduction of tyrosine kinase inhibitors had revolutionized the treatment of CML over the years; however, there is a need for developing tailoring therapy to individual risk since the patient clinical heterogeneity poses a major problem during drug response. Therefore, the study of basic clinical picture may aid in planning treatment strategies for CML patients. Aim: The aim of this article is to study the epidemiological and clinical variables associated with the prognosis of CML. Subjects and Methods: We have considered the distribution of various demographic and clinical variables among 476 CML patients diagnosed at Nizam’s Institute of Medical Sciences, Hyderabad, Telangana, India. Statistical Analysis Used: All the analyses were performed through SPSS software (version 21.0). Correlation and Cox regression analyses were also performed. Results: Apart from the elevated male sex ratio in CML incidence, high frequency of males was observed to be nonresponders to imatinib mesylate (IM). IM response was shown to be dependent on phase of diagnosis, whereas overall survival of CML patients depends on the age at onset and response to IM. Conclusions: The study of epidemiology and clinical picture of CML patients may help in planning better treatment strategies at diagnosis to achieve long-term progression-free survival.

Understanding, justifying, and optimizing radiation exposure for CT imaging in nephrourology

An estimated 4-5 million CT scans are performed in the USA every year to investigate nephrourological diseases such as urinary stones and renal masses. Despite the clinical benefits of CT imaging, concerns remain regarding the potential risks associated with exposure to ionizing radiation. To assess the potential risk of harmful biological effects from exposure to ionizing radiation, understanding the mechanisms by which radiation damage and repair occur is essential. Although radiation level and cancer risk follow a linear association at high doses, no strong relationship is apparent below 100 mSv, the doses used in diagnostic imaging. Furthermore, the small theoretical increase in risk of cancer incidence must be considered in the context of the clinical benefit derived from a medically indicated CT and the likelihood of cancer occurrence in the general population. Elimination of unnecessary imaging is the most important method to reduce imaging-related radiation; however, technical aspects of medically justified imaging should also be optimized, such that the required diagnostic information is retained while minimizing the dose of radiation. Despite intensive study, evidence to prove an increased cancer risk associated with radiation doses below ~100 mSv is lacking; however, concerns about ionizing radiation in medical imaging remain and can affect patient care. Overall, the principles of justification and optimization must remain the basis of clinical decision-making regarding the use of ionizing radiation in medicine.

Hematopoietic stem and progenitor cell responses to low radiation doses - implications for leukemia risk

Studies of the responses of hematopoietic stem and progenitor cells (HSPCs) to low doses of ionizing radiation formed an important aspect of the RISK-IR project ( www.risk-ir.eu ). A brief overview of these studies is presented here. The findings confirm the sensitivity of HSPCs to radiation even at low doses, and illustrate the substantial impact that differentiation state has upon cell sensitivity. The work provides mechanistic support for epidemiological findings of leukemia risk at dose levels used in diagnostic CT imaging, and further suggests that low-dose irradiation may facilitate bone marrow transplantation, a finding that could lead to refinements in clinical practice.

Radiation databases and archives - examples and comparisons

Studies of ionizing radiation effects through the archiving of data began with standardizing medical treatments in the early 1900s shortly after the discovery of X-rays. Once the breadth of the delayed effects of ionizing radiation was recognized, the need for long-term follow up became apparent. There are now many human archives of data from nuclear disasters and accidents, occupational exposures, and medical procedures. Planned animal irradiation experiments began around the time of the Cold War and included a variety of doses, fractions, dose rates, and types of ionizing radiation. The goal of most of these studies was to supplement information coming from human data through carefully planned experimental conditions and immediate and uninterrupted data collection. This review aims to highlight major archives and databases that have shaped the field of radiation biology and provide a broad range of the types of datasets currently available. By preserving all of these data and tissue sets, radiation biologists can combine databases and conduct large-scale analyses of detailed existing data and perform new assays with cutting edge scientific approaches.

The impact of dose rate on the linear no threshold hypothesis

The goal of this manuscript is to define the role of dose rate and dose protraction on the induction of biological changes at all levels of biological organization. Both total dose and the time frame over which it is delivered are important as the body has great capacity to repair all types of biological damage. The importance of dose rate has been recognized almost from the time that radiation was discovered and has been included in radiation standards as a Dose, Dose Rate, Effectiveness Factor (DDREF) and a Dose Rate Effectiveness Factor (DREF). This manuscript will evaluate the role of dose rate at the molecular, cellular, tissue, experimental animals and humans to demonstrate that dose rate is an important variable in estimating radiation cancer risk and other biological effects. The impact of low-dose rates on the Linear-No-Threshold Hypothesis (LNTH) will be reviewed since if the LNTH is not valid it is not possible to calculate a single value for a DDREF or DREF. Finally, extensive human experience is briefly reviewed to show that the radiation risks are not underestimated and that radiation at environmental levels has limited impact on total human cancer risk.

Epidemiological studies of atomic bomb radiation at the Radiation Effects Research Foundation

Epidemiological studies of people who were exposed to atomic bomb radiation and their children who were conceived after parental exposure to radiation (F₁) have investigated late health effects of atomic bomb radiation and its transgenerational effects. Those studies were initiated by the Atomic Bomb Casualty Commission (ABCC) in the 1950s. ABCC was reorganized to the Radiation Effects Research Foundation (RERF) in 1975, which continued the work of the ABCC. Follow-up of vital status and cause of death is performed for all RERF cohorts, including the atomic bomb survivors (the Life Span Study: LSS), in utero survivors, and the children of the survivors (F₁). Cancer incidence is investigated for accessible subpopulations of the cohorts. Health examinations for subcohorts of the LSS and in utero survivors are conducted as the Adult Health Study (AHS); a program of health examinations for a subcohort of the F₁ study is called the F₁ Offspring Clinical Study (FOCS). Participants of all clinical programs are asked to donate their blood and urine for storage and future biomedical investigations. Epidemiological studies have observed increased radiation risks for malignant diseases among survivors including those exposed in utero, and possible risks for some noncancer diseases. No increased risks due to parental exposure to radiation have been observed for malignancies or other diseases in F₁, but continuing investigations are required.

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.

Evaluation of the Incidence of Hematologic Malignant Neoplasms Among Breast Cancer Survivors in France

IMPORTANCE

Breast cancer survivors are at an increased risk of developing certain types of hematologic malignant neoplasm after diagnosis.

OBJECTIVE

To estimate the incidence of various types of hematologic malignant neoplasm in breast cancer survivors, both in absolute terms and in association with the general population.

DESIGN, SETTING, AND PARTICIPANTS

This nationwide cohort study conducted in France used data from the French National Health Data System, a database that contains all of French residents' health-related expenses. All French women aged 20 to 85 years with an incident breast cancer diagnosis between July 1, 2006, and December 31, 2015, were included (n = 439 704) and followed up until hematologic malignant neoplasm occurrence, death, loss of follow-up, or December 31, 2016, whichever came first. Comparisons were made with all French women in the general population who were registered in the French general health insurance program each year from January 1, 2007, and December 31, 2016. Data analysis was performed from January 23, 2018, to May 25, 2018.

MAIN OUTCOMES AND MEASURES

Main outcomes were incident hematologic malignant neoplasm cases occurring at least 6 months after breast cancer diagnosis. The various types of hematologic malignant neoplasm considered were acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), myeloproliferative neoplasms (MPNs), multiple myeloma (MM), Hodgkin lymphoma or non-Hodgkin lymphoma (HL/NHL), and acute lymphoblastic leukemia or lymphocytic lymphoma (ALL/LL). Incidence of these various types was estimated among breast cancer survivors and compared with the incidence in women in the general population.

RESULTS

The 439 704 women in the study had a median (interquartile range [IQR]) age of 59 (50-69) years and were followed up for a median (IQR) duration of 5 (2.8-7.5) years. Overall, 3046 cases of hematologic malignant neoplasm occurred: 509 cases (16.7%) of AML (crude incidence rate [CIR] per 100 000 person-years, 24.5; 95% CI, 22.4-26.8), 832 cases (27.3%) of MDS (CIR, 40.1; 95% CI, 37.4-42.9), and 267 cases (8.8%) of MPN (CIR, 12.8; 95% CI, 11.4-14.5). Lymphoid neoplasm cases included 420 cases (13.8%) of MM (CIR, 20.3; 95% CI, 18.4-22.3), 912 cases (29.9%) of HL/NHL (CIR, 44.4; 95% CI, 41.1-50.0), and 106 cases (3.5%) of ALL/LL (CIR, 5.1; 95% CI, 4.2-6.2). Compared with the general population, breast cancer survivors had statistically significantly higher incidence of AML (standardized incidence rate ratio [SIRR], 2.8; 95% CI, 2.5-3.2) and MDS (SIRR, 5.0; 95% CI, 4.4-5.7) and, to a lesser extent, MM (SIRR, 1.5; 95% CI, 1.3-1.7]) and ALL/LL (SIRR, 2.0; 95% CI, 1.3-3.0).

CONCLUSIONS AND RELEVANCE

The finding that AML and MDS still occur among breast cancer survivors today, and that ALL/LL and MM may also be of concern, merits the continuous monitoring of hematologic malignant neoplasms and the thorough investigations into their underlying mechanisms.

Human Lymphocyte Metaphase Chromosome Preparation for Radiation-Induced Chromosome Aberration Analysis

Radiation-induced chromosomal aberration analysis for metaphase chromosomes is well established and the golden standard for human biodosimetry. This method can estimate doses of human radiation exposure after nuclear accident and unwanted radiation exposure from their lymphocytes. The natural background frequency of dicentric chromosome for human lymphocytes is less than 1% and any increase in dicentric and centric ring chromosomes may be highly associated with radiation exposure. With the appropriate number of metaphase cells, one can detect the exposure of more than 0.1 Gy by observing dicentric and centric ring chromosomes. Dicentric chromosome analysis is relying on morphological changes and may be difficult for researchers without appropriate training. This method is time consuming and labor intensive, but still currently the most reliable technique and analysis needs only light microscopes with high magnification objectives and trained personnel. Recent research enables us to visualize dicentric chromosomes clearly with fluorescent markers for easy detection of dicentric and centric ring chromosomes. This chapter will introduce classical dicentric analysis of human lymphocyte cells with Giemsa staining.

Incidence of chronic myeloid leukemia in Calgary, Alberta, Canada

OBJECTIVE

The epidemiology of chronic myeloid leukemia is shifting due to the aging global population and the recent discovery and availability of targeted treatment options. This study provides recent data regarding the incidence of CML in Calgary, a major Canadian city. Data from patients diagnosed with CML by bone marrow sample analysis from 2011 to 2015 were collected from the database of the sole centralized cytogenetics facility in service of Calgary and its surrounding area.

RESULTS

With an average of 10.2 newly diagnosed cases per year in Calgary from 2011 to 2015, the incidence rate was calculated to be 0.75 cases per 100,000 person-years (95% CI 0.57-0.99). With age standardization, the incidence was 0.87 cases per 100,000 person-years (95% CI 0.82-0.91) for the Canadian population, which was low compared to other developed Western nations. The highest incidence rates were observed in the older patient categories, however there was a broad age distribution for incident cases and the median age at diagnosis was 48. There was a general male bias for CML most pronounced at the younger ages. Our description of CML incidence will help to inform healthcare planners amidst the dramatically altered treatment of this hematological neoplasm.

Risk of acute myeloid leukemia and myelodysplastic syndrome after autotransplants for lymphomas and plasma cell myeloma

BACKGROUND

Exposures to DNA-damaging drugs and ionizing radiations increase risks of acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS).

METHODS

9028 recipients of hematopoietic cell autotransplants (1995-2010) for Hodgkin lymphoma (HL; n = 916), non-Hodgkin lymphoma (NHL; n = 3546) and plasma cell myeloma (PCM; n = 4566), reported to the CIBMTR, were analyzed for risk of subsequent AML or MDS.

RESULTS

335 MDS/AML cases were diagnosed posttransplant (3.7%). Variables associated with an increased risk for AML or MDS in multivariate analyses were: (1) conditioning with total body radiation versus chemotherapy alone for HL (HR = 4.0; 95% confidence interval [1.4, 11.6]) and NHL (HR = 2.5 [1.1, 2.5]); (2) ≥3 versus 1 line of chemotherapy for NHL (HR = 1.9 [1.3, 2.8]); and (3) subjects with NHL transplanted in 2005-2010 versus 1995-1999 (HR = 2.1 [1.5, 3.1]). Using Surveillance, Epidemiology and End Results (SEER) data, we found risks for AML/MDS in HL, NHL and PCM to be 5-10 times the background rate. In contrast, relative risks were 10-50 for AML and approximately 100 for MDS in the autotransplant cohort.

CONCLUSIONS

There are substantial risks of AML and MDS after autotransplants for HL, NHL and PCM.

Subtle excess in lifetime cancer risk related to CT scanning in Spanish young people

BACKGROUND

CT scan is a life-saving medical diagnostic tool, entailing higher levels of ionising radiation exposure than conventional radiography, which may result in an increase in cancer risk, particularly in children. Information about the use and potential health effects of CT scan imaging among young people in Spain is scarce.

OBJECTIVE

This paper aims to estimate the number of radiation-related cancer cases which can be expected due to the use of CT scanning in Spanish children and young adults in a single year (2013).

METHODS

The 2013 distribution of number and types of CT scans performed in young people was obtained for Catalonia and extrapolated to the whole Spain. Organ doses were estimated based on the technical characteristics of 17,406 CT examinations extracted from radiology records. Age and sex-specific data on cancer incidence and life tables were obtained for the Spanish population. Age and sex-specific risk models developed by the Committee on Health Risks of Exposure to Low Levels of Ionizing Radiations (BEIR VII) and Berrington de Gonzalez were used, together, with the dose estimates to derive the lifetime attributable risks of cancer in Spain due to one year of CT scanning and project the number of future cancer cases to be expected.

RESULTS

In 2013, 105,802 CT scans were estimated to have been performed in people younger than age 21. It was estimated that a total of 168.6 cancer cases (95% CrI: 30.1-421.1) will arise over life due to the ionising radiation exposure received during these CTs. Lifetime attributable risks per 100,000 exposed patients were highest for breast and lung cancer. The largest proportion of CTs was to the head and neck and hence the highest numbers of projected cancer cases were of thyroid and oral cavity/pharynx.

CONCLUSIONS

Despite the undeniable medical effectiveness of CT scans, this risk assessment suggests a small excess in cancer cases which underlines the need for justification and optimisation in paediatric scanning. Given the intrinsic uncertainties of these risk projection exercises, care should be taken when interpreting the predicted risks.

Persistence of radiation-induced aberrations in patients after radiotherapy with C-ions and IMRT

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A follow-up of aberrations in lymphocytes of cancer patients was performed.

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The ratio of dicentrics to translocations declined indicating bone marrow damage.

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Bone marrow exposure was verified by examination of treatment plans.

•

Clonal aberrations were also present before therapy and thus not radiation induced.

Background and purpose

Chromosomal aberrations in peripheral blood lymphocytes are a biomarker for radiation exposure and are associated with an increased risk for malignancies. To determine the long-term cytogenetic effect of radiotherapy, we analyzed the persistence of different aberration types up to 2.5 years after the treatment.

Materials and methods

Cytogenetic damage was analyzed in lymphocytes from 14 patients that had undergone C-ion boost + IMRT treatment for prostate cancer. Samples were taken immediately, 1 year and 2.5 years after therapy. Aberrations were scored using the multiplex fluorescence in situ hybridization technique and grouped according to their transmissibility to daughter cells.

Results

Dicentric chromosomes (non-transmissible) and translocations (transmissible) were induced with equal frequencies. In the follow-up period, the translocation yield remained unchanged while the yield of dicentrics decreased to ≈40% of the initial value (p = 0.011 and p = 0.001 for 1 and 2.5 years after compared to end of therapy). In 2 patients clonal aberrations were observed; however they were also found in samples taken before therapy and thus were not radiotherapy induced.

Conclusion

The shift in the aberrations spectrum towards a higher fraction of translocations indicates the exposure of hematopoietic stem and progenitor cells underlining the importance of a careful sparing of bone marrow during radiotherapy to minimize the risk for secondary cancers.

Evidence for dose and dose rate effects in human and animal radiation studies

For stochastic effects such as cancer, linear-quadratic models of dose are often used to extrapolate from the experience of the Japanese atomic bomb survivors to estimate risks from low doses and low dose rates. The low dose extrapolation factor (LDEF), which consists of the ratio of the low dose slope (as derived via fitting a linear-quadratic model) to the slope of the straight line fitted to a specific dose range, is used to derive the degree of overestimation (if LDEF > 1) or underestimation (if LDEF < 1) of low dose risk by linear extrapolation from effects at higher doses. Likewise, a dose rate extrapolation factor (DREF) can be defined, consisting of the ratio of the low dose slopes at high and low dose rates. This paper reviews a variety of human and animal data for cancer and non-cancer endpoints to assess evidence for curvature in the dose response (i.e. LDEF) and modifications of the dose response by dose rate (i.e. DREF). The JANUS mouse data imply that LDEF is approximately 0.2-0.8 and DREF is approximately 1.2-2.3 for many tumours following gamma exposure, with corresponding figures of approximately 0.1-0.9 and 0.0-0.2 following neutron exposure. This paper also cursorily reviews human data which allow direct estimates of low dose and low dose rate risk.

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.

Implications of recent epidemiologic studies for the linear nonthreshold model and radiation protection

The recently published NCRP Commentary No. 27 evaluated the new information from epidemiologic studies as to their degree of support for applying the linear nonthreshold (LNT) model of carcinogenic effects for radiation protection purposes (NCRP 2018 Implications of Recent Epidemiologic Studies for the Linear Nonthreshold Model and Radiation Protection, Commentary No. 27 (Bethesda, MD: National Council on Radiation Protection and Measurements)). The aim was to determine whether recent epidemiologic studies of low-LET radiation, particularly those at low doses and/or low dose rates (LD/LDR), broadly support the LNT model of carcinogenic risk or, on the contrary, demonstrate sufficient evidence that the LNT model is inappropriate for the purposes of radiation protection. An updated review was needed because a considerable number of reports of radiation epidemiologic studies based on new or updated data have been published since other major reviews were conducted by national and international scientific committees. The Commentary provides a critical review of the LD/LDR studies that are most directly applicable to current occupational, environmental and medical radiation exposure circumstances. This Memorandum summarises several of the more important LD/LDR studies that incorporate radiation dose responses for solid cancer and leukemia that were reviewed in Commentary No. 27. In addition, an overview is provided of radiation studies of breast and thyroid cancers, and cancer after childhood exposures. Non-cancers are briefly touched upon such as ischemic heart disease, cataracts, and heritable genetic effects. To assess the applicability and utility of the LNT model for radiation protection, the Commentary evaluated 29 epidemiologic studies or groups of studies, primarily of total solid cancer, in terms of strengths and weaknesses in their epidemiologic methods, dosimetry approaches, and statistical modelling, and the degree to which they supported a LNT model for continued use in radiation protection. Recommendations for how to make epidemiologic radiation studies more informative are outlined. The NCRP Committee recognises that the risks from LD/LDR exposures are small and uncertain. The Committee judged that the available epidemiologic data were broadly supportive of the LNT model and that at this time no alternative dose-response relationship appears more pragmatic or prudent for radiation protection purposes.

Is there an epidemic of chronic lymphocytic leukaemia (CLL) in China?

BACKGROUND

Chronic lymphocytic leukaemia (CLL) is 10- to 20-fold less common in Asians (including Han Chinese) compared with persons of predominately European descent. Why is unknown but seems predominately genetic. We observed an increasing frequency of new cases of CLL at our Haematology Centre beginning 2011 and wondered why.

OBJECTIVE

Determine the cause(s) for this increased frequency.

METHOD

We interrogated the context of CLL diagnosis in 483 consecutive subjects seen at the Institute of Haematology of a large referral hospital in Beijing. 3 cohorts were considered based on why a CBC was done to establish the CLL diagnosis: (1) a CBC-testing situation unrelated to a health condition such as a routine annual health exam or application for employment or medical insurance (termed routine CBC); (2) an unrelated medical condition such as a cold, influenza, heart disease etc. (termed CBC for other disorders); and (3) signs and/or symptoms consistent with CLL such as lymph-adenopathy, hepato- or splenomegaly, fatigue, B-symptoms etc. (termed CBC for possible CLL).

RESULTS

Data regarding context of CLL diagnosis were available for 389 subjects (81%). Proportions of subjects in the 3 cohorts were 44% (95% confidence interval [CI]; 39, 49%), 24% (20, 28%) and 32% (28, 37%). The proportion of subjects whose evaluation of CLL was prompted by an abnormal CBC not for possible CLL (cohorts 1 and 2) increased over the surveillance interval (r = 0.164; P = 0.001) as did median age at diagnosis (r = 0.207; P < 0.001). Age at diagnosis was correlated with probability of CLL being suspected because of an abnormal routine CBC (r = 0.249; P < 0.001); 42% (32, 53%) amongst subjects ≤50 years versus 86% (75, 92%; P < 0.001) among those >70 years. Consistent with this, older subjects were diagnosed at Rai stage-0 with asymptomatic disease compared with younger subjects (P < 0.001).

CONCLUSION

Our data suggest much of the increased frequency of CLL at our centre and likely elsewhere in China predominately reflects ascertainment bias. Other variables may also operate.

Cancer mortality and incidence following external occupational radiation exposure: an update of the 3rd analysis of the UK national registry for radiation workers

BACKGROUND

This study provides direct evidence of cancer risk from low dose and dose rate occupational external radiation exposures.

METHODS

Cancer mortality and incidence were studied in relation to external radiation exposure in the National Registry for Radiation Workers. A cohort of 167,003 workers followed for an average of 32 years was analysed using Poisson regression methods.

RESULTS

Mortality and incidence risks were significantly raised for the group of all malignant neoplasms excluding leukaemia (ERR/Sv mortality = 0.28; 90%CI: 0.06, 0.53, ERR/Sv incidence = 0.28; 90%CI: 0.10, 0.48) but with narrower confidence bounds compared with the previous analysis of this cohort reflecting the increased statistical power from the additional 10 years of follow-up information. The linear trends in relative risk for both mortality and incidence of these cancers remained statistically significantly raised when information relating to cumulative doses above 100 mSv was excluded (ERR/Sv mortality = 1.42; 90%CI: 0.51, 2.38 and ERR/Sv incidence = 1.18; 90%CI: 0.47, 1.92).

CONCLUSIONS

This study improved the precision of the cancer risk estimates seen in the third analysis of the NRRW cohort. The overall results remain consistent with the risk estimates from the Life Span Study and those adopted in the current ICRP recommendations.

Radiation-Induced Myofibroblasts Promote Tumor Growth via Mitochondrial ROS-Activated TGFβ Signaling

Fibroblasts are a key stromal cell in the tumor microenvironment (TME) and promote tumor growth via release of various growth factors. Stromal fibroblasts in cancer, called cancer-associated fibroblasts (CAF), are related to myofibroblasts, an activated form of fibroblast. While investigating the role of stroma fibroblasts on radiation-related carcinogenesis, it was observed following long-term fractionated radiation (FR) that the morphology of human diploid fibroblasts changed from smaller spindle shapes to larger flat shapes. These cells expressed smooth muscle actin (α-SMA) and platelet-derived growth factor receptors, markers of myofibroblasts and CAFs, respectively. Long-term FR induces progressive damage to the fibroblast nucleus and mitochondria via increases in mitochondrial reactive oxygen species (ROS) levels. Here, it is demonstrated that long-term FR-induced α-SMA-positive cells have decreased mitochondrial membrane potential and activated oxidative stress responses. Antioxidant N-acetyl cysteine suppressed radiation-induced mitochondrial damage and generation of myofibroblasts. These results indicate that mitochondrial ROS are associated with the acquisition of myofibroblasts after long-term FR. Mechanistically, mitochondrial ROS activated TGFβ signaling which in turn mediated the expression of α-SMA in radiation-induced myofibroblasts. Finally, in vivo tumor growth analysis in a human tumor xenograft model system revealed that long-term FR-induced myofibroblasts promote tumor growth by enhancing angiogenesis.Implications: Radiation affects malignant cancer cells directly and indirectly via molecular alterations in stromal fibroblasts such as activation of TGFβ and angiogenic signaling pathways. Mol Cancer Res; 16(11); 1676-86. ©2018 AACR.

Leukaemia and myeloid malignancy among people exposed to low doses (<100 mSv) of ionising radiation during childhood: a pooled analysis of nine historical cohort studies

BACKGROUND

Substantial evidence links exposure to moderate or high doses of ionising radiation, particularly in childhood, with increased risk of leukaemia. The association of leukaemia with exposure to low-dose (<100 mSv) radiation is less certain, although this is the dose range most relevant to the general population. We aimed to estimate the risk of leukaemia associated with low-dose radiation exposure in childhood (age <21 years).

METHODS

In this analysis of historical cohort studies, we pooled eligible cohorts reported up to June 30, 2014. We evaluated leukaemia and myeloid malignancy outcomes in these cohorts with the relevant International Classification of Diseases and International Classification of Diseases for Oncology definitions. The cohorts included had not been treated for malignant disease, had reported at least five cases of the relevant haematopoietic neoplasms, and estimated individual active bone marrow (ABM) doses. We restricted analysis to individuals who were younger than 21 years at first irradiation who had mean cumulative ABM doses of less than 100 mSv. Dose-response models were fitted by use of Poisson regression. The data were received in fully anonymised form by the statistical analyst.

FINDINGS

We identified nine eligible cohorts from Canada, France, Japan, Sweden, the UK, and the USA, including 262 573 people who had been exposed to less than 100 mSv enrolled between June 4, 1915, and Dec 31, 2004. Mean follow-up was 19·63 years (SD 17·75) and mean cumulative ABM dose was 19·6 mSv (SD 22·7). 154 myeloid malignancies were identified (which included 79 acute myeloid leukaemias, eight myelodysplastic syndromes, and 36 chronic myeloid leukaemias, in addition to other unspecified myeloid malignancies) and 40 acute lymphoblastic leukaemias, with 221 leukaemias (including otherwise unclassified leukaemias but excluding chronic lymphocytic leukaemia) identified overall. The fitted relative risks at 100 mSv were 3·09 (95% CI 1·41-5·92; p_trend=0·008) for acute myeloid leukaemia and myelodysplastic syndromes combined, 2·56 (1·09-5·06; p_trend=0·033) for acute myeloid leukaemia, and 5·66 (1·35-19·71; p_trend=0·023) for acute lymphoblastic leukaemia. There was no clear dose-response for chronic myeloid leukaemia, which had a relative risk at 100 mSv of 0·36 (0·00-2·36; p_trend=0·394). There were few indications of between-cohort heterogeneity or departure from linearity. For acute myeloid leukaemia and myelodysplastic syndromes combined and for acute lymphoblastic leukaemia, the dose-responses remained significant for doses of less than 50 mSv. Excess absolute risks at 100 mSv were in the range of 0·1-0·4 cases or deaths per 10 000 person-years.

INTERPRETATION

The risks of acute myeloid leukaemia and acute lymphoblastic leukaemia were significantly increased after cumulative doses of ionising radiation of less than 100 mSv in childhood or adolescence, with an excess risk also apparent for cumulative radiation doses of less than 50 mSv for some endpoints. These findings support an increased risk of leukaemia associated with low-dose exposure to radiation and imply that the current system of radiological protection is prudent and not overly protective.

FUNDING

National Cancer Institute Intramural Research Program, National Cancer Institute, and US National Institutes for Health.

Radiation exposure from computerized tomography and risk of childhood leukemia: Finnish register-based case-control study of childhood leukemia (FRECCLE)

The only well-established risk factors for childhood leukemia are high-dose ionizing radiation and Down syndrome. Computerized tomography is a common source of low-dose radiation. In this study, we examined the magnitude of the risk of childhood leukemia after pediatric computed tomography examinations. We evaluated the association of computed tomography scans with risk of childhood leukemia in a nationwide register-based case-control study. Cases (n=1,093) were identified from the population-based Finnish Cancer Registry and three controls, matched by gender and age, were randomly selected for each case from the Population Registry. Information was also obtained on birth weight, maternal smoking, parental socioeconomic status and background gamma radiation. Data on computed tomography scans were collected from the ten largest hospitals in Finland, covering approximately 87% of all pediatric computed tomography scans. Red bone marrow doses were estimated with NCICT dose calculation software. The data were analyzed using exact conditional logistic regression analysis. A total of 15 cases (1.4%) and ten controls (0.3%) had undergone one or more computed tomography scans, excluding a 2-year latency period. For one or more computed tomography scans, we observed an odds ratio of 2.82 (95% confidence interval: 1.05 – 7.56). Cumulative red bone marrow dose from computed tomography scans showed an excess odds ratio of 0.13 (95% confidence interval: 0.02 – 0.26) per mGy. Our results are consistent with the notion that even low doses of ionizing radiation observably increase the risk of childhood leukemia. However, the observed risk estimates are somewhat higher than those in earlier studies, probably due to random error, although unknown predisposing factors cannot be ruled out.

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.

Investigation of Spatial Organization of Chromosome Territories in Chromosome Exchange Aberrations After Ionizing Radiation Exposure

Higher-order organization of the human genome is well established with chromosomes occupying distinct domains or territories in the interphase nucleus. Spatial organization of chromosome territories in the interphase nucleus occurs in a cell-type-specific manner. Since both stable and unstable aberrations induced by ionizing radiation involve the exchange of material between two or more chromosomes, this study investigated the role of spatial organization of chromosome domains in ionizing-radiation-induced chromosome translocation events. Using multicolor fluorescence in situ hybridization, the study characterized the positioning of each human chromosome relative to its neighborhood territories in the interphase nucleus of lymphocytes and B-lymphoblastoid cells before ionizing radiation and compared this interphase positioning with the spectrum of exchanges observed after ionizing radiation in the metaphase chromosomes. In addition to multicolor fluorescence in situ hybridization, the genome-wide chromosome conformation capture technique (Hi-C) was also performed in mock and x-ray-irradiated human B-lymphoblastoid and fibroblast cells to characterize the interactions among chromosomes and to assess the genome reorganization changes, if any, after ionizing radiation exposure. On average, 35-50% of the total translocations induced by x rays and neutrons correlated with proximity of chromosome territories detected by multicolor fluorescence in situ hybridization in both lymphocytes and lymphoblastoid cells. The translocation rate observed in proximally positioned chromosome territories was consistently higher than distally located territories and was found to be statistically significant (p = 0.01) in human lymphoblastoid cells after x rays. The interchromosome interaction frequencies detected by Hi-C correlate fairly well with ionizing-radiation-induced translocations detected by multicolor fluorescence in situ hybridization, suggesting the importance of chromosome proximity effects in ionizing-radiation-induced chromosomal translocation events.

Probability Distribution of Dose and Dose-Rate Effectiveness Factor for use in Estimating Risks of Solid Cancers From Exposure to Low-Let Radiation

This paper presents an analysis to develop a subjective state-of-knowledge probability distribution of a dose and dose-rate effectiveness factor for use in estimating risks of solid cancers from exposure to low linear energy transfer radiation (photons or electrons) whenever linear dose responses from acute and chronic exposure are assumed. A dose and dose-rate effectiveness factor represents an assumption that the risk of a solid cancer per Gy at low acute doses or low dose rates of low linear energy transfer radiation, RL, differs from the risk per Gy at higher acute doses, RH; RL is estimated as RH divided by a dose and dose-rate effectiveness factor, where RH is estimated from analyses of dose responses in Japanese atomic-bomb survivors. A probability distribution to represent uncertainty in a dose and dose-rate effectiveness factor for solid cancers was developed from analyses of epidemiologic data on risks of incidence or mortality from all solid cancers as a group or all cancers excluding leukemias, including (1) analyses of possible nonlinearities in dose responses in atomic-bomb survivors, which give estimates of a low-dose effectiveness factor, and (2) comparisons of risks in radiation workers or members of the public from chronic exposure to low linear energy transfer radiation at low dose rates with risks in atomic-bomb survivors, which give estimates of a dose-rate effectiveness factor. Probability distributions of uncertain low-dose effectiveness factors and dose-rate effectiveness factors for solid cancer incidence and mortality were combined using assumptions about the relative weight that should be assigned to each estimate to represent its relevance to estimation of a dose and dose-rate effectiveness factor. The probability distribution of a dose and dose-rate effectiveness factor for solid cancers developed in this study has a median (50th percentile) and 90% subjective confidence interval of 1.3 (0.47, 3.6). The harmonic mean is 1.1, which implies that the arithmetic mean of an uncertain estimate of the risk of a solid cancer per Gy at low acute doses or low dose rates of low linear energy transfer radiation is only about 10% less than the mean risk per Gy at higher acute doses. Data were also evaluated to define a low acute dose or low dose rate of low linear energy transfer radiation, i.e., a dose or dose rate below which a dose and dose-rate effectiveness factor should be applied in estimating risks of solid cancers.

Risk of subsequent myeloid neoplasms after radiotherapy treatment for a solid cancer among adults in the United States, 2000-2014

Although increased risk of acute myeloid leukemia (AML) has been observed after chemotherapy and radiotherapy, less is known about radiotherapy-related risks of specific AML subtypes and other specific myeloid neoplasms. We used the US population-based cancer registry data to evaluate risk of myeloid neoplasms among three cohorts of cancer survivors initially treated with radiotherapy only. We included 1-year survivors of first primary thyroid (radioiodine only, stages I-IV; N = 49 879), prostate (excluding stage IV; N = 237 439), or uterine corpus cancers (stage I-II; N = 16 208) diagnosed during 2000-2013. We calculated standardized incidence ratios (SIRs) and excess absolute risks (EARs). Thyroid cancer survivors had significantly elevated risks of total AML (SIR = 2.77, 95% CI: 1.99-3.76), AML with cytogenetic abnormalities (SIR = 3.90, 95% CI: 1.57-8.04), AML with myelodysplasia-related changes (SIR = 2.87, 95% CI: 1.05-6.25), and BCR-ABL1-positive chronic myelogenous leukemia (CML) (SIR = 5.38, 95% CI: 2.58-9.89). Irradiated prostate and uterine corpus cancer survivors were at elevated risk for total AML (SIR = 1.14, 95% CI: 1.03-1.27 and SIR = 1.77, 95% CI: 1.01-2.87, respectively), AML with cytogenetic abnormalities (SIR = 2.52, 95% CI: 1.84-3.37 and SIR = 7.21, 95% CI: 2.34-16.83, respectively), and acute promyelocytic leukemia (SIR = 3.20, 95% CI: 2.20-4.49 and SIR = 8.88, 95% CI: 2.42-22.73, respectively). In addition, prostate cancer survivors were at increased risk of BCR-ABL1-positive CML (SIR = 2.11, 95% CI: 1.52-2.85). Our findings support the importance of diagnostic precision in myeloid neoplasm classification since susceptibility following radiotherapy may vary by myeloid neoplasm subtype, thereby informing risk/benefit discussions in first primary cancer treatment.

Genomic characterization of chronic lymphocytic leukemia (CLL) in radiation-exposed Chornobyl cleanup workers

BACKGROUND

Chronic lymphocytic leukemia (CLL) was the predominant leukemia in a recent study of Chornobyl cleanup workers from Ukraine exposed to radiation (UR-CLL). Radiation risks of CLL significantly increased with increasing bone marrow radiation doses. Current analysis aimed to clarify whether the increased risks were due to radiation or to genetic mutations in the Ukrainian population.

METHODS

A detailed characterization of the genomic landscape was performed in a unique sample of 16 UR-CLL patients and age- and sex-matched unexposed general population Ukrainian-CLL (UN-CLL) and Western-CLL (W-CLL) patients (n = 28 and 100, respectively).

RESULTS

Mutations in telomere-maintenance pathway genes POT1 and ATM were more frequent in UR-CLL compared to UN-CLL and W-CLL (both p < 0.05). No significant enrichment in copy-number abnormalities at del13q14, del11q, del17p or trisomy12 was identified in UR-CLL compared to other groups. Type of work performed in the Chornobyl zone, age at exposure and at diagnosis, calendar time, and Rai stage were significant predictors of total genetic lesions (all p < 0.05). Tumor telomere length was significantly longer in UR-CLL than in UN-CLL (p = 0.009) and was associated with the POT1 mutation and survival.

CONCLUSIONS

No significant enrichment in copy-number abnormalities at CLL-associated genes was identified in UR-CLL compared to other groups. The novel associations between radiation exposure, telomere maintenance and CLL prognosis identified in this unique case series provide suggestive, though limited data and merit further investigation.

Glyphosate Use and Cancer Incidence in the Agricultural Health Study

Background

Glyphosate is the most commonly used herbicide worldwide, with both residential and agricultural uses. In 2015, the International Agency for Research on Cancer classified glyphosate as "probably carcinogenic to humans," noting strong mechanistic evidence and positive associations for non-Hodgkin lymphoma (NHL) in some epidemiologic studies. A previous evaluation in the Agricultural Health Study (AHS) with follow-up through 2001 found no statistically significant associations with glyphosate use and cancer at any site.

Methods

The AHS is a prospective cohort of licensed pesticide applicators from North Carolina and Iowa. Here, we updated the previous evaluation of glyphosate with cancer incidence from registry linkages through 2012 (North Carolina)/2013 (Iowa). Lifetime days and intensity-weighted lifetime days of glyphosate use were based on self-reported information from enrollment (1993-1997) and follow-up questionnaires (1999-2005). We estimated incidence rate ratios (RRs) and 95% confidence intervals (CIs) using Poisson regression, controlling for potential confounders, including use of other pesticides. All statistical tests were two-sided.

Results

Among 54 251 applicators, 44 932 (82.8%) used glyphosate, including 5779 incident cancer cases (79.3% of all cases). In unlagged analyses, glyphosate was not statistically significantly associated with cancer at any site. However, among applicators in the highest exposure quartile, there was an increased risk of acute myeloid leukemia (AML) compared with never users (RR = 2.44, 95% CI = 0.94 to 6.32, Ptrend = .11), though this association was not statistically significant. Results for AML were similar with a five-year (RRQuartile 4 = 2.32, 95% CI = 0.98 to 5.51, Ptrend = .07) and 20-year exposure lag (RRTertile 3 = 2.04, 95% CI = 1.05 to 3.97, Ptrend = .04).

Conclusions

In this large, prospective cohort study, no association was apparent between glyphosate and any solid tumors or lymphoid malignancies overall, including NHL and its subtypes. There was some evidence of increased risk of AML among the highest exposed group that requires confirmation.

Japanese Legacy Cohorts: The Life Span Study Atomic Bomb Survivor Cohort and Survivors' Offspring

Cohorts of atomic bomb survivors—including those exposed in utero—and children conceived after parental exposure were established to investigate late health effects of atomic bomb radiation and its transgenerational effects by the Atomic Bomb Casualty Commission (ABCC) in the 1950s. ABCC was reorganized to the Radiation Effects Research Foundation (RERF) in 1975, and all work has been continued at RERF. The Life Span Study, the cohort of survivors, consists of about 120,000 subjects and has been followed since 1950. Cohorts of in utero survivors and the survivors’ children include about 3,600 and 77,000 subjects, respectively, and have been followed since 1945. Atomic bomb radiation dose was estimated for each subject based on location at the time of the bombing and shielding conditions from exposure, which were obtained through enormous efforts of investigators and cooperation of subjects. Outcomes include vital status, cause of death, and cancer incidence. In addition, sub-cohorts of these three cohorts were constructed to examine clinical features of late health effects, and the subjects have been invited to periodic health examinations at clinics of ABCC and RERF. They were also asked to donate biosamples for biomedical investigations. Epidemiological studies have observed increased radiation risks for malignant diseases among survivors, including those exposed in utero, and possible risks for some non-cancer diseases. In children of survivors, no increased risks due to parental exposure to radiation have been observed for malignancies or other diseases, but investigations are continuing, as these cohorts are still relatively young.

Tracking preleukemic cells in vivo to reveal the sequence of molecular events in radiation leukemogenesis

Epidemiological studies have demonstrated an increased leukemia incidence following ionizing radiation exposure, but to date, the target cells and underlying mechanisms of radiation leukemogenesis remain largely unidentified. We engineered a mouse model carrying a different fluorescent marker on each chromosome 2, located inside the minimum deleted region occurring after radiation exposure and recognized as the first leukemogenic event. Using this tailored model, we report that following radiation exposure, more than half of asymptomatic CBA Sfpi1^GFP/mCh mice presented with expanding clones of preleukemic hematopoietic cells harboring a hemizygous interstitial deletion of chromosome 2. Moreover, following isolation of preleukemic hematopoietic stem and progenitor cells irradiated in their native microenvironment, we identified the presence of Sfpi1 point mutations within a subpopulation of these preleukemic cells expanding rapidly (increasing from 6% to 55% in 21 days in peripheral blood in one case), hence identifying for the first time the presence of such cells within a living animal. Importantly, we also report a previously undescribed gender difference in the phenotype of the preleukemic cells and leukemia, suggesting a gender imbalance in the radiation-induced leukemic target cell. In conclusion, we provide novel insights into the sequence of molecular events occurring during the (radiation-induced) leukemic clonal evolution.

Dose-responses for mortality from cerebrovascular and heart diseases in atomic bomb survivors: 1950-2003

The scientific community faces important discussions on the validity of the linear no-threshold (LNT) model for radiation-associated cardiovascular diseases at low and moderate doses. In the present study, mortalities from cerebrovascular diseases (CeVD) and heart diseases from the latest data on atomic bomb survivors were analyzed. The analysis was performed with several radio-biologically motivated linear and nonlinear dose-response models. For each detrimental health outcome one set of models was identified that all fitted the data about equally well. This set was used for multi-model inference (MMI), a statistical method of superposing different models to allow risk estimates to be based on several plausible dose-response models rather than just relying on a single model of choice. MMI provides a more accurate determination of the dose response and a more comprehensive characterization of uncertainties. It was found that for CeVD, the dose-response curve from MMI is located below the linear no-threshold model at low and medium doses (0-1.4 Gy). At higher doses MMI predicts a higher risk compared to the LNT model. A sublinear dose-response was also found for heart diseases (0-3 Gy). The analyses provide no conclusive answer to the question whether there is a radiation risk below 0.75 Gy for CeVD and 2.6 Gy for heart diseases. MMI suggests that the dose-response curves for CeVD and heart diseases in the Lifespan Study are sublinear at low and moderate doses. This has relevance for radiotherapy treatment planning and for international radiation protection practices in general.