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

Genetic association between coffee consumption and multiple myeloma mediated by plasma metabolites: a Mendelian randomization study

Background: Multiple myeloma (MM) is a hematologic malignancy closely associated with diets and metabolic disorders, showing an increasing incidence trend. Genome-wide association studies (GWAS) contribute to exploring the causal relationships between diets, metabolites, and MM, thereby revealing biological mechanisms underlying cancer progression. Methods: This study included large-scale GWAS data for two diets, four metabolomics, and MM. The two-sample Mendelian randomization (MR) analysis was conducted to assess causalities between these dietary patterns, metabolites, and MM. The MR analysis primarily employed the inverse variance weighted (IVW) method, supported by multiple sensitivity analysis and reverse MR analysis to validate significant associations. Mediation analysis identified specific metabolites mediating the causal relationships between diets and MM. Results: Univariate MR analysis suggested that coffee consumption (ORIVW = 2.72; 95% CI: 1.21-6.10; PIVW = 0.015, P_fdr = 0.022), decaffeinated coffee consumption (ORIVW = 7.10; 95% CI: 1.33-37.87; PIVW = 0.022, P_fdr = 0.022), ground coffee consumption (ORIVW = 4.04; 95% CI: 1.25-13.02; PIVW = 0.019, P_fdr = 0.022), instant coffee consumption (ORIVW = 6.13; 95% CI: 1.95-19.34; PIVW = 0.002, P_fdr = 0.008), and coffee max liking (ORIVW = 2.94; 95% CI: 1.23-7.03; PIVW = 0.015, P_fdr = 0.035) were associated with increased MM risk. Metabolomic MR analysis identified 19 plasma metabolites, 1 blood and urine biomarker, and 4 plasma lipids with significant association with MM. Mediation analysis indicated that hippurate and cinnamoylglycine mediated 35.55% (P < 0.001) and 21.85% (P = 0.002) of the genetically predicted effect of coffee consumption on MM risk, respectively. Cinnamoylglycine contributed 12.63% (P = 0.042) to the total causal effect of ground coffee consumption on MM. Hippurate (21.43%, P < 0.001), 3-hydroxyhippurate (4.39%, P = 0.031), and cinnamoylglycine (8.79%, P = 0.010) mediated the genetically predicted impact of instant coffee consumption on MM risk. Metabolic pathway analysis suggested that glutathione metabolism significantly contributes to MM pathogenesis (P = 0.002, FDR < 0.05). Conclusions: Our findings support the adverse causal effects of various coffee consumption on MM risk, identifying hippurate, 3-hydroxyhippurate, and cinnamoylglycine as key mediators, driving the relationship potentially through the glutathione metabolism pathway.

Timing and trajectory of BCR::ABL1-driven chronic myeloid leukaemia

Mutation of some genes drives uncontrolled cell proliferation and cancer. The Philadelphia chromosome in chronic myeloid leukaemia (CML) provided the very first such genetic link to cancer1,2. However, little is known about the trajectory to CML, the rate of BCR::ABL1 clonal expansion and how this affects disease. Using whole-genome sequencing of 1,013 haematopoietic colonies from nine patients with CML aged 22 to 81 years, we reconstruct phylogenetic trees of haematopoiesis. Intronic breaks in BCR and ABL1 were not always observed, and out-of-frame exonic breakpoints in BCR, requiring exon skipping to derive BCR::ABL1, were also noted. Apart from ASXL1 and RUNX1 mutations, extra myeloid gene mutations were mostly present in wild-type cells. We inferred explosive growth attributed to BCR::ABL1 commencing 3-14 years (confidence interval 2-16 years) before diagnosis, with annual growth rates exceeding 70,000% per year. Mutation accumulation was higher in BCR::ABL1 cells with shorter telomere lengths, reflecting their excessive cell divisions. Clonal expansion rates inversely correlated with the time to diagnosis. BCR::ABL1 in the general population mirrored CML incidence, and advanced and/or blast phase CML was characterized by subsequent genomic evolution. These data highlight the oncogenic potency of BCR::ABL1 fusion and contrast with the slow and sequential clonal trajectories of most cancers.

High-dose radiation preferentially induces the clonal expansion of hematopoietic progenitor cells over mature T and B cells in mouse bone marrow

Radiation induces clonal hematopoiesis (CH) involving high-frequency somatic mutations in hematopoietic cells. However, the effects of radiation on clonal expansion of hematopoietic progenitor cells and lymphocytes remain elusive. Here, we investigate CH mutations and T cell receptor (TCR) and B cell receptor (BCR) sequences within the bone marrow cells of mice 18 months after irradiation (3 Gy) and age-matched controls. Two to six CH mutations were identified in the irradiated mice (N = 5), while only one of the four control mice carried a CH mutation. These CH mutations detected in the bone marrow were also identified in the splenic CD11b+ myeloid cell population. Meanwhile, the cumulative size of the ten largest TCR and BCR clones, as well as their clonality, did not differ significantly between irradiated and control mice. Our findings suggest that radiation preferentially induces clonal expansion of hematopoietic progenitor cells over mature lymphocytes in the bone marrow.

Cancer risk due to ingestion of naturally occurring radionuclides through drinking water: A systematic review

Naturally occurring radionuclides can, in rare cases, reach high levels in drinking water of specific areas, leading to meaningful radiation exposures upon ingestion. Increased cancer risk is the only well-established health impact of exposure to low-dose radiation. Multiple ecological studies have shown conflicting results about cancer risk in areas of high levels of radionuclides in water. However, such studies have methodological limitations and are generally not highly informative. Studies with individual-level data are scarce and have not established a clear association either. To further investigate this issue, we conducted a systematic review of the literature on cancer risk associated with radionuclide ingestion through drinking water, aiming to summarize and evaluate the current epidemiological evidence. Published studies have examined the effects of uranium, radium, and radon, while potential risks of polonium, radioactive lead, and thorium remain unknown. Existing research is heterogeneous regarding the cancer types assessed and faces methodological challenges, including limitations in exposure assessment, dosimetric uncertainties, low statistical power, and inadequate control of confounding factors. Due to lack of high-quality evidence, it is not possible to confirm or rule out an increased cancer risk among highly exposed populations. While risk assessment based on extrapolation from high dose studies does not suggest an excess cancer risk beyond background variation, such assessment involves considerable uncertainties. Future studies should focus on populations with high radionuclide exposure to provide sufficient exposure contrast, prioritizing radionuclides with high-dose coefficients and cancers in tissues with the highest radionuclide deposition.

Let's talk about radiation dose and radiation protection in children

Children are more sensitive to ionizing radiation than adults. Even though the risk is very low, exposure from radiological examinations can possibly cause them long-term side effects. Recent large epidemiological studies involving children and young adults have added evidence suggesting that even small doses of radiation, such as those from computed tomography scans, might slightly increase the risk of developing cancer later in life. Therefore, even though radiologic studies are essential for an accurate diagnosis and management of various conditions, it is crucial to minimize radiation exposure. This article addresses radiation protection for children in the medical use of ionizing radiation and it is set in the context of the European legislative framework regarding radiation protection. It advocates for a holistic approach to paediatric radiological tests. This approach includes the key principles of radiation protection, such as the justification of imaging procedures supported by referral guidelines, as well as the optimization of techniques (according to the ALARA principle) and effective communication with parents about the benefits and the risks of radiologic procedures. Protecting children from unnecessary radiation is not only a technical challenge, but also a moral obligation and a legal requirement.

What about the workers? An update

Epidemiological studies of nuclear industry workers are of substantial importance to understanding the risk of cancer consequent to low-level exposure to radiation, and these studies should provide vital evidence for the construction of the international system of radiological protection. Recent studies involve large numbers of workers and include health outcomes for workers who accumulated moderate (and even high) doses over prolonged periods while employed during the earlier years of the nuclear industry. The interpretation of the findings of these recent studies has proved to be disappointingly difficult. There are puzzling patterns of results involving the period of first employment and monitoring for radionuclide intakes, depending on the particular study examined. Explaining these patterns is crucial for a reliable understanding of results in terms of occupational radiation exposure. In this paper, an updated review of nuclear worker studies is presented in the context of these patterns of results, making use of the latest relevant results. It is apparent that the strikingly raised risks for mortality from solid cancers for workers hired in later years reported from the International Nuclear Workers Study (INWORKS) is effectively confined to workers at five nuclear facilities in the USA, and that the notable variation of risks in INWORKS between workers monitored or not for radionuclide intakes is driven by UK workers. These are the areas where effort must be concentrated before a confident derivation of radiation risk estimates can be obtained from these nuclear worker studies.

The Effects of Cosmic Radiation Exposure on Pregnancy During a Probable Manned Mission to Mars

Space missions have revealed certain disincentive factors of this unique environment, such as microgravity, cosmic radiation, etc., as the aerospace industry has made substantial progress in exploring deep space and its impacts on human body. Galactic cosmic radiation (GCR), a form of ionizing radiation, is one of those environmental factors that has potential health implications and, as a result, may limit the duration - and possibly the occurrence - of deep-space missions. High doses of cosmic radiation exposure during spaceflight, particularly during exploration class missions, may have teratogenic effects on a developing fetus, if an unintended pregnancy occurs shortly before or during the flight. This study aimed to discuss whether the cumulative dosage for a pregnant woman during a probable manned mission to Mars may exceed the terrestrial teratogenic radiation limit. A variety of studies, technical documents, and publications that provided flight duration data and the absorbed cosmic radiation dosage equivalents between Earth and Mars were analyzed. A literature-based hypothetical model of a pregnancy simulation over a 6-month spaceflight was also designed to estimate the cumulative absorbed GCR dose. The estimated dose rates ranged from 90 to 324 mSv. Assuming that a pregnant crew member is exposed to this dosage range, the total teratogenic dose equivalent to the embryo/fetus appear to be significantly higher than that of the National Council on Radiation Protection (NCRP)'s and United States Nuclear Regulatory Commission (USNRC)'s recommendations, which state a maximum radiation dose of 5 mSv for the duration of the pregnancy, and thus such an exceeded dose may likely result in teratogenesis. Current protective strategies may not be sufficient to protect the human genome from the detrimental effects of cosmic radiation, and they need be improved for long-term interplanetary travels during human colonization of Mars.

Integration of multi-omics and benchmark dose modeling to support adverse outcome pathways

BACKGROUND

Recent advancements in omics and benchmark dose (BMD) modeling have facilitated identifying the dose required for a predetermined change in a response (e.g. gene or protein change) that can be used to establish acceptable dose levels for hazardous exposures. Adverse Outcome Pathways (AOPs) describe the causal links between toxicants and adverse effects through key events (KEs). Integrating omics data within the AOP framework quantitatively links early molecular events to later phenotypic effects. In this study, we use omic-based BMD analyses in an in vitro blood model exposed to radiation to identify point of departure (POD) values across KEs to acute myeloid leukemia (www.aopwiki.org/aop/432).

METHODS

Isolated white blood cells were cultured and X-irradiated (1 Gy/minute, 0-6 Gy). Transcriptomic and proteomic changes were assessed 24 h post-exposure. BMD modeling was applied and significantly perturbed genes/proteins and pathways were identified. Those pathways relevant to KEs outlined in AOP 432 were grouped and a POD was determined.

RESULTS

BMD modeling identified 1294 genes and 167 proteins with median BMD lower confident limit (BMD) values of 1.35 and 0.32 Gy, respectively. Pathway analysis identified biological processes related to DNA damage/repair, oxidative stress, cell cycle regulation, immune responses, and cancer development. These findings aligned with the KEs in AOP 432. The BMDL values of canonical pathways associated with these KEs were generally below 0.5 Gy with specific genes (e.g. GADD45A) displaying BMDLs <0.05 Gy.

CONCLUSIONS

This work provides insights into predictive radiation induced mechanisms and associated dose of activity that can be taken into consideration for low dose (< 0.1 Gy) risk analysis.

Radiophobia Harm, Its Main Cause, and a Proposed Solution

Background: We are exposed to natural ionizing radiation and other genomic stressors throughout life and radiophobia has caused much harm to society. The main basis for radiophobia is the invalid linear no-threshold (LNT) hypothesis for cancer induction, which the System of Radiological Protection (SRP) is linked to. Largely unknown to the public, evolution-associated genomic stress adaptation (gensadaptation) over many previous generations now provides protection to all lifeforms from low radiation doses. Objective: To help bring about an improved SRP not linked to the invalid LNT hypothesis for radiation-caused health detriment and to promote low-dose radiation therapy for different diseases. Methods: All-solid-cancer mortality risk dose-response relationships for A-bomb survivors were generated based on published LNT-modeling-related results. Dose-response relationships for lung cancer prevention by low-dose radiation were generated by linear interpolation based on published data from a study using > 15,000 mice. Uncertainty characterization was based on Monte Carlo calculations for binomial and Poisson distributions. New dose characterization tools were used for threshold dose-response relationships for radiation-caused cancer mortality. Results: The all-solid-cancer mortality risk for A-bomb survivors transitioned from LNT to threshold-linear when adjusted for key missing uncertainty at low doses. The prevention of lung cancer in mice by low radiation doses depends on the radiation absorbed dose and type. Conclusions: The SRP should be linked to population dose thresholds rather than the invalid LNT hypothesis and small likely harmless radiation doses could possibly be used in treating different diseases.

Myelodysplastic syndromes among atomic bomb survivors in Nagasaki: similarities to and differences from de novo and therapy-related cases

Epidemiological studies for atomic bomb (A-bomb) survivors clearly demonstrated that A-bomb radiation increased the risk of hematological neoplasms, such as acute and chronic leukemia, and myelodysplastic syndromes (MDS) among survivors. Several studies on MDS among survivors investigated its characteristics, and it seems that MDS among survivors has different features from those seen in de novo MDS and therapy-related MDS. In this short review, we describe the differences of clinical features, chromosomal alterations and genome aberrations among them.

A note on potential gains in precision of radiation risk estimates from joint analysis

In estimating radiation-related risk of cancer and other diseases based on the RERF Life Span Study (LSS), joint analyses can be performed where multiple health outcome endpoints are combined in the same model, allowing some parameters to be estimated in common among all endpoints with possible increase in precision of radiation risk and other model parameter estimates. Using as a basis excess relative risk (ERR) and excess absolute risk (EAR) models of the type commonly used in analysis of LSS data at RERF, we use maximum likelihood theory to compute the asymptotic relative standard error of endpoint-specific radiation effect and other parameter estimates using joint analyses as compared to traditional independent analysis. We show that some gains in precision of endpoint-specific radiation risk parameter estimates can be achieved by sharing effect modifier and other model parameters, but only small or negligible gains in precision are achieved for endpoint-specific background modifying or effect modifying parameters when other model parameters are shared. The magnitude of the precision gain for radiation risk estimates depends on the number of endpoints, the baseline incidence rate of the endpoint, and the type of model being used.

Updated findings on temporal variation in radiation-effects on cancer mortality in an international cohort of nuclear workers (INWORKS)

The International Nuclear Workers Study (INWORKS) contributes knowledge on the dose-response association between predominantly low dose, low dose rate occupational exposures to penetrating forms of ionizing radiation and cause-specific mortality. By extending follow-up of 309,932 radiation workers from France (1968-2014), the United Kingdom (1955-2012), and the United States (1944-2016) we increased support for analyses of temporal variation in radiation-cancer mortality associations. Here, we examine whether age at exposure, time since exposure, or attained age separately modify associations between radiation and mortality from all solid cancers, solid cancers excluding lung cancer, lung cancer, and lymphohematopoietic cancers. Multivariable Poisson regression was used to fit general relative rate models that describe modification of the linear excess relative rate per unit organ absorbed dose. Given indication of greater risk per unit dose for solid cancer mortality among workers hired in more recent calendar years, sensitivity analyses considering the impact of year of hire on results were performed. Findings were reasonably compatible with those from previous pooled and country-specific analyses within INWORKS showing temporal patterns of effect measure modification that varied among cancers, with evidence of persistent radiation-associated excess cancer risk decades after exposure, although statistically significant temporal modification of the radiation effect was not observed. Analyses stratified by hire period (< 1958, 1958+) showed temporal patterns that varied; however, these analyses did not suggest that this was due to differences in distribution of these effect measure modifiers by hire year.

Sex-Based Differences in Risk of Therapy-Related Myeloid Neoplasms

PURPOSE

Therapy-related myeloid neoplasm (t-MN) is a life-threatening complication of autologous peripheral blood stem cell (PBSC) transplantation for non-Hodgkin lymphoma (NHL). Previous studies report an association between clonal hematopoiesis (CH) in PBSC and risk of t-MN, but small samples precluded examination of risk within specific subpopulations.

METHODS

Targeted DNA sequencing was performed to identify CH mutations in PBSC from a retrospective cohort of 984 patients with NHL (median age at transplant, 57 years; range, 18-78). Fine-Gray proportional subdistribution hazard regression models estimated association between number of CH mutations and t-MN, adjusting for demographic, clinical, and therapeutic variables. Secondary analyses evaluated the association between CH and t-MN among males and females.

RESULTS

CH was identified in PBSC from 366 patients (37.2%). t-MN developed in 60 patients after a median follow-up of 5 years. Presence of ≥2 mutations conferred increased t-MN risk (adjusted hazard ratio [aHR], 2.10; 95% CI [1.08 to 4.11]; P = .029). CH was associated with increased t-MN risk among males (aHR, 1.83 [95% CI, 1.01 to 3.31]) but not females (aHR, 0.56 [95% CI, 0.15 to 2.09]). Although the prevalence and type of CH mutations in PBSC were comparable, the 8-year cumulative incidence of t-MN was higher among males vs. females with CH (12.4% v 3.6%) but was similar between males and females without CH (4.9% v 3.9%). Expansion of CH clones from PBSC to t-MN was seen only among males.

CONCLUSION

presence of CH mutations in PBSC confers increased risk of t-MN after autologous transplantation in male but not female patients with NHL. Factors underlying sex-based differences in risk of CH progression to t-MN merit further investigation.

Influence of Age on Leukemia Mortality Associated with Exposure to γ rays and 2-MeV Fast Neutrons in Male C3H Mice

The relative biological effectiveness (RBE) of densely ionizing radiation can depend on the biological context. From a radiological perspective, age is an important factor affecting health risks of radiation exposure, but little is known about the modifying impact of age on the effects of densely ionizing radiation. Herein, we addressed the influence of age on leukemogenesis induced by accelerator-generated fast neutrons (mean energy, ∼2 MeV). Male C3H/HeNrs mice were exposed to 137Cs γ rays (0.2-3.0 Gy) or neutrons (0.0485-0.97 Gy, γ ray contamination 0.0105-0.21 Gy) at 1, 3, 8, or 35 weeks of age and observed over their lifetimes under specific pathogen-free conditions. Leukemia and lymphoma were diagnosed pathologically. Hazard ratio (HR) and RBE for myeloid leukemia mortality as well as the age dependence of these two parameters were modeled and analyzed using Cox regression. Neutron exposure increased HR concordant with a linear dose response. The increase of HR per dose depended on age at exposure, with no significant dose dependence at age 1 or 3 weeks but a significant increase in HR of 5.5 per Gy (γ rays) and 16 per Gy (neutrons) at 8 weeks and 5.8 per Gy (γ rays) and 9 per Gy (neutrons) at 35 weeks. The RBE of neutrons was 2.1 (95% confidence interval, 1.1-3.7), with no dependence on age. The development of lymphoid neoplasms was not related to radiation exposure. The observed increasing trend of radiation-associated mortality of myeloid leukemia with age at exposure supports previous epidemiological and experimental findings. The results also suggest that exposure at the susceptible age of 8 or 35 weeks does not significantly influence the RBE value for neutrons for induction of leukemia, unlike what has been documented for breast and brain tumors.

Leukaemia, lymphoma, and multiple myeloma mortality after low-level exposure to ionising radiation in nuclear workers (INWORKS): updated findings from an international cohort study

BACKGROUND

A major update to the International Nuclear Workers Study (INWORKS) was undertaken to strengthen understanding of associations between low-dose exposure to penetrating forms of ionising radiation and mortality. Here, we report on associations between radiation dose and mortality due to haematological malignancies.

METHODS

We assembled a cohort of 309 932 radiation-monitored workers (269 487 [87%] males and 40 445 [13%] females) employed for at least 1 year by a nuclear facility in France (60 697 workers), the UK (147 872 workers), and the USA (101 363 workers). Workers were individually monitored for external radiation exposure and followed-up from Jan 1, 1944, to Dec 31, 2016, accruing 10·72 million person-years of follow-up. Radiation-mortality associations were quantified in terms of the excess relative rate (ERR) per Gy of radiation dose to red bone marrow for leukaemia excluding chronic lymphocytic leukaemia (CLL), as well as subtypes of leukaemia, myelodysplastic syndromes, non-Hodgkin and Hodgkin lymphomas, and multiple myeloma. Estimates of association were obtained using Poisson regression methods.

FINDINGS

The association between cumulative dose to red bone marrow, lagged 2 years, and leukaemia (excluding CLL) mortality was well described by a linear model (ERR per Gy 2·68, 90% CI 1·13 to 4·55, n=771) and was not modified by neutron exposure, internal contamination monitoring status, or period of hire. Positive associations were also observed for chronic myeloid leukaemia (9·57, 4·00 to 17·91, n=122) and myelodysplastic syndromes alone (3·19, 0·35 to 7·33, n=163) or combined with acute myeloid leukaemia (1·55, 0·05 to 3·42, n=598). No significant association was observed for acute lymphoblastic leukaemia (4·25, -4·19 to 19·32, n=49) or CLL (0·20, -1·81 to 2·21, n=242). A positive association was observed between radiation dose and multiple myeloma (1·62, 0·06 to 3·64, n=527) whereas minimal evidence of association was observed between radiation dose and non-Hodgkin lymphoma (0·27, -0·61 to 1·39, n=1146) or Hodgkin lymphoma (0·60, -3·64 to 4·83, n=122) mortality.

INTERPRETATION

This study reports a positive association between protracted low dose exposure to ionising radiation and mortality due to some haematological malignancies. Given the relatively low doses typically accrued by workers in this study (16 mGy average cumulative red bone marrow dose) the radiation attributable absolute risk of leukaemia mortality in this population is low (one excess death in 10 000 workers over a 35-year period). These results can inform radiation protection standards and will provide input for discussions on the radiation protection system.

FUNDING

National Cancer Institute, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Institut de Radioprotection et de Sûreté Nucléaire, Orano, Electricité de France, UK Health Security Agency.

TRANSLATION

For the French translation of the abstract see Supplementary Materials section.

INWORKS and Hiroshima/Nagasaki Leukaemia Results

The Hiroshima/Nagasaki (H/N) studies by the Radiation Effect Research Foundation have not shown increased leukaemia for acute doses below 200 milli-gray (mGy). By contrast the INWORKS study of leukaemia in workers stated: "This study provides strong evidence of positive associations between protracted low-dose radiation exposure and leukemia". The INWORKS study also claimed increased leukaemia, not including Chronic Lymphocytic Leukaemia, at cumulative occupational doses of less than 100 mGy. This is contrary to the expectation that the H/N studies would show more severe effects than the worker study because the doses were acute instead of chronic and because the H/N studies included children who had higher rates of radiation induced leukaemia than adults. This paper shows that the INWORKS leukaemia study is consistent with the H/N studies in showing no increase in leukaemia in the low-dose range. In addition, any increase in leukaemia is confined to Chronic Myeloid Leukaemia, possibly from high radiation dose-rates or chemicals.

miR-4716-3p and the target AKT2 Gene/rs2304186 SNP are associated with blood cancer pathogenesis in Pakistani population

AKT2 is crucial for cancer cells' invasion, metastasis, and survival. It is a possible downstream gene target of cancer glycolysis-related microRNAs. The study investigated the role of miRNA-4716-3p, rs2304186, and the AKT2 gene in blood cancer pathogenesis. RT-qPCR was used to analyze AKT2 gene mRNA and miRNA-4716-3p expression in 200 blood cancer samples and 200 healthy controls. Furthermore, Tetra-ARMS PCR was used to examine the rs2304186 AKT2 SNP in 300 patients and 290 control samples. miRNA-4716-3p was shown to be significantly downregulated (p = 0.0294), whereas mRNA expression of the AKT2 gene was found to be significantly upregulated (p = 0.0034) in blood cancer patients compared to healthy individuals. miRNA-4716-3p downregulation (p = 0.0466) was more pronounced, while AKT2 upregulation was non-significant (p = 0.1661) in untreated patients compared to chemotherapy-treated patients. Blood cancer risk was significantly associated with the rs2304186 GT genotype (p = 0.0432), TT genotype (p = 0.0502), and mutant allele (T) frequency (p = 0.0008). Polymorphism rs2304186 was associated with an increased risk of blood cancer in dominant (p = 0.0011), recessive (p = 0.0502), and additive (p = 0.0008) genetic models. The results suggested that the rs2304186 and the deregulated expression of miRNA-4716-3p and AKT2 gene at the mRNA level may significantly increase the incidence of blood cancer, particularly in the Pakistani population. Therefore, these may function as suitable biomarkers for blood cancer diagnosis and prognosis. Additional, larger-scale investigations may be required to affirm these results.

A Historical Survey of Key Epidemiological Studies of Ionizing Radiation Exposure

In this article we review the history of key epidemiological studies of populations exposed to ionizing radiation. We highlight historical and recent findings regarding radiation-associated risks for incidence and mortality of cancer and non-cancer outcomes with emphasis on study design and methods of exposure assessment and dose estimation along with brief consideration of sources of bias for a few of the more important studies. We examine the findings from the epidemiological studies of the Japanese atomic bomb survivors, persons exposed to radiation for diagnostic or therapeutic purposes, those exposed to environmental sources including Chornobyl and other reactor accidents, and occupationally exposed cohorts. We also summarize results of pooled studies. These summaries are necessarily brief, but we provide references to more detailed information. We discuss possible future directions of study, to include assessment of susceptible populations, and possible new populations, data sources, study designs and methods of analysis.

Radioactive Iodine Therapy in Differentiated Thyroid Cancer: An Update on Dose Recommendations and Risk of Secondary Primary Malignancies

Radioactive iodine (RAI) therapy with iodine-131 is performed in select cases of differentiated thyroid cancer (DTC), typically for remnant ablation, adjuvant therapy, or treatment of known persistent disease. Herein, we review updated RAI dose recommendations and associated risks of secondary primary malignancy (SPM). RAI dose is usually chosen empirically based on the risk assessment of tumor recurrence and other factors. Dose recommendations differ slightly among relevant medical societies. As of April 2024, most medical societies, including the American Thyroid Association (ATA), European Thyroid Association (ETA), Society of Nuclear Medicine and Molecular Imaging/European Association of Nuclear Medicine (SNMMI/ EANM), and National Comprehensive Cancer Network (NCCN), recommend a dose of 1.11 GBq (30 mCi) I-131 for remnant ablation. For adjuvant therapy, the recommended RAI dose ranges from 1.11 to 3.7 GBq (30-100) mCi I-131, although doses up to 5.6 GBq (150 mCi) may also be considered. In patients with known or suspected metastatic disease, at least 3.7 GBq (100 mCi) I-131 should be administered, and RAI doses as high as 7.4 GBq (200 mCi) may be justified depending on the suspected tumor burden and extent. Dosimetry has the advantage of tailoring the RAI dose to each patient's pharmacokinetics, resulting in ≥ 7.4 GBq (200 mCi) of I-131 in most cases. There is an ongoing debate about the risk of developing SPM due to RAI therapy, with several multicenter studies and meta-analyses concerning SPM being published in the last 2 years. The incidence of RAI-associated SPM varies according to the study design and detection method. Several studies showed no increased incidence, and there was no specific secondary cancer or cancer group linked to RAI exposures. Some reports indicated that cumulative RAI doses exceeding 5.6-7.4 GBq (150-200 mCi) were found to represent an increased risk for developing SPM. However, a clearly defined dose threshold cannot be provided based on the current literature. Nonetheless, caution should be exercised when considering repeated RAI therapies for persistent metastatic PTC, with a cumulative dose exceeding 37.0 GBq (1,000 mCi), due to the potential risk of developing SPM and other long-term toxicity. Further research is warranted to understand better the relationship between RAI dose and the risk of SPM.

Cancer risk associated with low-dose ionizing radiation: A systematic review of epidemiological and biological evidence

The current radiation protection reference standards on stochastic cancer risk, drafted by the International Committee on Radiation Protection, are mostly based on the Life Span Study (LSS), though sufficient epidemiological and basic research evidence is lacking. The relationship between low-dose ionizing radiation (LDIR) and cancer risk is currently modeled with linear non-threshold (LNT) models. However, with the widespread use of medical examinations, the demand for substantial evidence of cancer risk under LDIR and the establishment of a threshold has become more significant. In the first part of the review, we summarize pivotal research in epidemiology, which includes the LSS, medical radiation studies, and occupational and environmental exposure studies. We describe and discuss solid cancers and hematopoietic malignancies induced by LDIR separately, attempting to identify the consistency and differences in the research results, and offering suggestions for future research directions. In the second part, we review recent progress in the underlying biology of cancer associated with LDIR. Besides the obvious harmful effect of DNA damage, chromosome aberrations caused by LDIR, epigenetic regulation also requires attention due to their relationship with carcinogenic and genetic risk. The multistage carcinogenesis model of stem cells, along with the varying effects of radiation on different tumors, may challenge the LNT model. Related research of stem cells, mitochondria and omic biology also offers promising directions for future research in this field.

Mechanisms Underlying the Development of Murine T-Cell Lymphoblastic Lymphoma/Leukemia Induced by Total-Body Irradiation

Exposure to ionizing radiation is associated with an increased risk of hematologic malignancies in myeloid and lymphoid lineages in humans and experimental mice. Given that substantial evidence links radiation exposure with the risk of hematologic malignancies, it is imperative to deeply understand the mechanisms underlying cellular and molecular changes during the latency period between radiation exposure and the emergence of fully transformed malignant cells. One experimental model widely used in the field of radiation and cancer biology to study hematologic malignancies induced by radiation exposure is mouse models of radiation-induced thymic lymphoma. Murine radiation-induced thymic lymphoma is primarily driven by aberrant activation of Notch signaling, which occurs frequently in human precursor T-cell lymphoblastic lymphoma (T-LBL) and T-cell lymphoblastic leukemia (T-ALL). Here, we summarize the literature elucidating cell-autonomous and non-cell-autonomous mechanisms underlying cancer initiation, progression, and malignant transformation in the thymus following total-body irradiation (TBI) in mice.

Low-Dose Radiation Risks of Lymphohematopoietic Cancer Mortality in U.S. Shipyard Workers

The linear, non-threshold (LNT) hypothesis of cancer induction derived from studies of populations exposed to moderate-to-high acute radiation doses may not be indicative of cancer risks associated with lifetime radiation exposures less than 100 mSv. The objective of this study was to examine risks and dose-response patterns of lymphohematopoietic cancer (LHC) and its types associated with low radiation exposure while adjusting for possible confounding factors. A retrospective cohort of 437,937 U.S. nuclear shipyard workers (153,930 radiation and 284,007 non-radiation workers) was followed from 1957 to 2011, with 3,699 LHC deaths observed. The risk of LHC in radiation workers was initially compared to the risk in non-radiation workers. Time dependent accumulated radiation dose, lagged 2 years, was used in categorical and continuous dose analysis among radiation workers to examine the LHC risks and possible dose-response relationships based on Poisson regression models. These analyses controlled for sex, race, time dependent age, calendar time, socioeconomic status, solvent-related last job, and age at first hire. The median lifetime radiation dose for the radiation worker population was 0.82 mSv and the 95th percentile dose was 83.63 mSv. The study shows: 1. LHC mortality for radiation workers was significantly lower than non-radiation workers relative risk: 0.927; 95% confidence intervals (95% CI): 0.865, 0.992; P = 0.030]. Among LHC types, the risks for lymphoid leukemia and lymphomas in radiation workers were lower than the risk in non-radiation workers with statistical significance, while the risk for the rest of LHC types did not show any statistically significant difference. 2. In categorical dose analysis among radiation workers, sample size weighted linear trend of relative risk (RRs) for LHC and its types in five dose categories (>0-<25, 25-<50, 50-<100, 100-<200, and > = 200 mSv) vs. 0 mSv were not statistically significant, although there was an elevation of RR for chronic myeloid leukemia only in the 50-<100 mSv category (RR: 2.746; 95% CI: 1.002, 7.521; P = 0.049) vs. 0 mSv. 3. The Poisson regression analyses among radiation workers using the time dependent radiation dose as a continuous variable showed an excess relative risk (ERR) for LHC at 100 mSv of 0.094 (95% CI: -0.037, 0.225; P = 0.158) and leukemia less chronic lymphoid leukemia, of 0.178 (95% CI: -0.085, 0.440; P = 0.440) vs. 0 mSv. The ERRs and their linear trend for all other types were not statistically significant.

Maternal Lifestyle and Prenatal Risk Factors for Childhood Leukemia: A Review of the Existing Evidence

BACKGROUND

Acute leukemia is the most common pediatric cancer, with an incidence peak at 2-5 years of age. Despite the medical advances improving survival rates, children suffer from significant side effects of treatments as well as its high social and economic impact. The frequent prenatal origin of this developmental disease follows the two-hit carcinogenesis model established in the 70s: a first hit in prenatal life with the creation of genetic fusion lesions or aneuploidy in hematopoietic progenitor/stem cells, and usually a second hit in the pediatric age that converts the preleukemic clone into clinical leukemia. Previous research has mostly focused on postnatal environmental factors triggering the second hit.

SUMMARY

There is scarce evidence on prenatal risk factors associated with the first hit. Mainly retrospective case-control studies suggested several environmental and lifestyle determinants as risk factors. If these associations could be confirmed, interventions focused on modifying prenatal factors might influence the subsequent risk of leukemia during childhood and reveal unexplored research avenues for the future. In this review, we aim to comprehensively summarize the currently available evidence on prenatal risk factors for the development of childhood leukemia. According to the findings of this review, parental age, ethnicity, maternal diet, folate intake, alcohol consumption, X-ray exposure, pesticides, perinatal infections, and fetal growth may have a significant role in the appearance of preleukemic lesions during fetal life. Other factors such as socioeconomic status, consumption of caffeinated beverages, and smoking consumption have been suggested with inconclusive evidence. Additionally, investigating the association between prenatal factors and genetic lesions associated with childhood leukemia at birth is crucial. Prospective studies evaluating the link between lifestyle factors and genetic alterations could provide indirect evidence supporting new research avenues for leukemia prevention. Maternal diet and lifestyle factors are modifiable determinants associated with adverse perinatal outcomes that could be also related to preleukemic lesions.

KEY MESSAGES

Parental age, ethnicity, maternal diet, folate intake, alcohol consumption, X-ray exposure, pesticides, perinatal infections, and fetal growth may have a significant role in the appearance of preleukemic lesions during fetal life. Dedicating efforts to studying maternal lifestyle during pregnancy and its association with genetic lesions leading to childhood leukemia could lead to novel prevention strategies.

A generalisation of the method of regression calibration and comparison with Bayesian and frequentist model averaging methods

For many cancer sites low-dose risks are not known and must be extrapolated from those observed in groups exposed at much higher levels of dose. Measurement error can substantially alter the dose-response shape and hence the extrapolated risk. Even in studies with direct measurement of low-dose exposures measurement error could be substantial in relation to the size of the dose estimates and thereby distort population risk estimates. Recently, there has been considerable attention paid to methods of dealing with shared errors, which are common in many datasets, and particularly important in occupational and environmental settings. In this paper we test Bayesian model averaging (BMA) and frequentist model averaging (FMA) methods, the first of these similar to the so-called Bayesian two-dimensional Monte Carlo (2DMC) method, and both fairly recently proposed, against a very newly proposed modification of the regression calibration method, the extended regression calibration (ERC) method, which is particularly suited to studies in which there is a substantial amount of shared error, and in which there may also be curvature in the true dose response. The quasi-2DMC with BMA method performs well when a linear model is assumed, but very poorly when a linear-quadratic model is assumed, with coverage probabilities both for the linear and quadratic dose coefficients that are under 5% when the magnitude of shared Berkson error is large (50%). For the linear model the bias is generally under 10%. However, using a linear-quadratic model it produces substantially biased (by a factor of 10) estimates of both the linear and quadratic coefficients, with the linear coefficient overestimated and the quadratic coefficient underestimated. FMA performs as well as quasi-2DMC with BMA when a linear model is assumed, and generally much better with a linear-quadratic model, although the coverage probability for the quadratic coefficient is uniformly too high. However both linear and quadratic coefficients have pronounced upward bias, particularly when Berkson error is large. By comparison ERC yields coverage probabilities that are too low when shared and unshared Berkson errors are both large (50%), although otherwise it performs well, and coverage is generally better than the quasi-2DMC with BMA or FMA methods, particularly for the linear-quadratic model. The bias of the predicted relative risk at a variety of doses is generally smallest for ERC, and largest for the quasi-2DMC with BMA and FMA methods (apart from unadjusted regression), with standard regression calibration and Monte Carlo maximum likelihood exhibiting bias in predicted relative risk generally somewhat intermediate between ERC and the other two methods. In general ERC performs best in the scenarios presented, and should be the method of choice in situations where there may be substantial shared error, or suspected curvature in the dose response.

A generalisation of the method of regression calibration and comparison with Bayesian and frequentist model averaging methods

For many cancer sites low-dose risks are not known and must be extrapolated from those observed in groups exposed at much higher levels of dose. Measurement error can substantially alter the dose-response shape and hence the extrapolated risk. Recently, there has been considerable attention paid to methods of dealing with shared errors, which are particularly important in occupational and environmental settings. In this paper we test Bayesian model averaging (BMA) and frequentist model averaging (FMA) methods, the first of these similar to the so-called Bayesian two-dimensional Monte Carlo (2DMC) method, and both fairly recently proposed, against a very newly proposed modification of the regression calibration method, the extended regression calibration (ERC) method. The quasi-2DMC+BMA method performs well when a linear model is assumed, but poorly when a linear-quadratic model is assumed. FMA performs as well as quasi-2DMC+BMA when a linear model is assumed, and generally much better with a linear-quadratic model, although the coverage probability for the quadratic coefficient is uniformly too high. ERC yields coverage probabilities that are too low when shared and unshared Berkson errors are both large (50%), although otherwise it performs well, and coverage is generally better than the quasi-2DMC+BMA or FMA methods, particularly for the linear-quadratic model. The bias of predicted relative risk at a variety of doses is generally smallest for ERC, and largest for quasi-2DMC+BMA and FMA, with standard regression calibration and Monte Carlo maximum likelihood exhibiting bias in predicted relative risk generally somewhat intermediate between ERC and the other two methods. In general ERC performs best in the scenarios presented, and should be the method of choice in situations where there may be substantial shared error, or suspected curvature in the dose response.

Multiple Myeloma and Occupational Risk Factors: A Narrative Review

Multiple Myeloma (MM) is a neoplastic hematologic disorder caused by the excessive proliferation of plasma cells and leads to bone lesions, anemia, and kidney failure. No definite etiology has been proposed for MM, but several environmental and genetic risk factors have been implicated so far. Exposure to pesticides, benzene, and organic solvents like methyl chloride have been considered a potential risk factor. Asbestos, ionizing radiation, and wood dust exposure have also been associated with MM. As MM is a relatively rare condition, the number of studies is insufficient, and in many studies, only a few study participants recall exposure to any agents. Therefore, establishing a definite risk factor is cumbersome and further studies with large study samples are needed. By recognizing these occupational risk factors, clinicians can encourage employees to reduce their exposure as more as possible and implement precautionary measures. In this review, we highlighted the current research on the potential association between occupational exposures and MM. Because of these studies, new regulations with the goal of occupational exposure reduction are anticipated in the future.

Time-integrated radiation risk metrics and interpopulation variability of survival

Task Group 115 of the International Commission on Radiological Protection is focusing on mission-related exposures to space radiation and concomitant health risks for space crew members including, among others, risk of cancer development. Uncertainties in cumulative radiation risk estimates come from the stochastic nature of the considered health outcome (i.e., cancer), uncertainties of statistical inference and model parameters, unknown secular trends used for projections of population statistics and unknown variability of survival properties between individuals or population groups. The variability of survival is usually ignored when dealing with large groups, which can be assumed well represented by the statistical data for the contemporary general population, either in a specific country or world averaged. Space crew members differ in many aspects from individuals represented by the general population, including, for example, their lifestyle and health status, nutrition, medical care, training and education. The individuality of response to radiation and lifespan is explored in this modelling study. Task Group 115 is currently evaluating applicability and robustness of various risk metrics for quantification of radiation-attributed risks of cancer for space crew members. This paper demonstrates the impact of interpopulation variability of survival curves on values and uncertainty of the estimates of the time-integrated radiation risk of cancer.

Non-targeted effects and space radiation risks for astronauts on multiple International Space Station and lunar missions

Future space travel to the earth's moon or the planet Mars will likely lead to the selection of experienced International Space Station (ISS) or lunar crew persons for subsequent lunar or mars missions. Major concerns for space travel are galactic cosmic ray (GCR) risks of cancer and circulatory diseases. However large uncertainties in risk prediction occur due to the quantitative and qualitative differences in heavy ion microscopic energy deposition leading to differences in biological effects compared to low LET radiation. In addition, there are sparse radiobiology data and absence of epidemiology data for heavy ions and other high LET radiation. Non-targeted effects (NTEs) are found in radiobiology studies to increase the biological effectiveness of high LET radiation at low dose for cancer related endpoints. In this paper the most recent version of the NASA Space Cancer Risk model (NSCR-2022) is used to predict mission risks while considering NTEs in solid cancer risk predictions. I discuss predictions of space radiation risks of cancer and circulatory disease mortality for US Whites and US Asian-Pacific Islander (API) populations for 6-month ISS, 80-day lunar missions, and combined ISS-lunar mission. Model predictions suggest NTE increase cancer risks by about ∼2.3 fold over a model that ignores NTEs. US API are predicted to have a lower cancer risks of about 30% compared to US Whites. Cancer risks are slightly less than additive for multiple missions, which is due to the decease of risk with age of exposure and the increased competition with background risks as radiation risks increase. The inclusion of circulatory risks increases mortality estimates about 25% and 37% for females and males, respectively in the model ignoring NTEs, and 20% and 30% when NTEs are assumed to modify solid cancer risk. The predictions made here for combined ISS and lunar missions suggest risks are within risk limit recommendations by the National Council on Radiation Protection and Measurements (NCRP) for such missions.

European astronaut radiation related cancer risk assessment using dosimetric calculations of organ dose equivalents

An illustrative sample mission of a Mars swing-by mission lasting one calendar year was chosen to highlight the application of European risk assessment software to cancer (all solid cancer plus leukaemia) risks from radiation exposures in space quantified with organ dose equivalent rates from model calculations based on the quantity Radiation Attributed Decrease of Survival (RADS). The relevant dose equivalent to the colon for radiation exposures from this Mars swing-by mission were found to vary between 198 and 482 mSv. These doses depend on sex and the two other factors investigated here of: solar activity phase (maximum or minimum); and the choice of space radiation quality factor used in the calculations of dose equivalent. Such doses received at typical astronaut ages around 40 years old will result in: the probability of surviving until retirement age (65 years) being reduced by a range from 0.38% (95%CI: 0.29; 0.49) to 1.29% (95%CI: 1.06; 1.56); and the probability of surviving cancer free until retirement age being reduced by a range from 0.78% (95%CI: 0.59; 0.99) to 2.63% (95%CI: 2.16; 3.18). As expected from the features of the models applied to quantify the general dosimetric and radiation epidemiology parameters, the cancer incidence risks in terms of surviving cancer free, are higher than the cancer mortality risks in terms of surviving, the risks for females are higher than for males, and the risks at solar minimum are higher than at solar maximum.

Radiation injury and gut microbiota-based treatment

The exposure to either medical sources or accidental radiation can cause varying degrees of radiation injury (RI). RI is a common disease involving multiple human body parts and organs, yet effective treatments are currently limited. Accumulating evidence suggests gut microbiota are closely associated with the development and prevention of various RI. This article summarizes 10 common types of RI and their possible mechanisms. It also highlights the changes and potential microbiota-based treatments for RI, including probiotics, metabolites, and microbiota transplantation. Additionally, a 5P-Framework is proposed to provide a comprehensive strategy for managing RI.

A generalisation of the method of regression calibration and comparison with the Bayesian 2-dimensional Monte Carlo method

For many cancer sites it is necessary to assess risks from low-dose exposures via extrapolation from groups exposed at moderate and high levels of dose. Measurement error can substantially alter the shape of this relationship and hence the derived population risk estimates. Even in studies with direct measurement of low-dose exposures measurement error could be substantial in relation to the size of the dose estimates and thereby distort population risk estimates. Recently, much attention has been devoted to the issue of shared errors, common in many datasets, and particularly important in occupational settings. In this paper we test a Bayesian model averaging method, the so-called Bayesian two-dimensional Monte Carlo (2DMC) method, that has been fairly recently proposed against a very newly proposed modification of the regression calibration method, which is particularly suited to studies in which there is a substantial amount of shared error, and in which there may also be curvature in the true dose response. We also compared both methods against standard regression calibration and Monte Carlo maximum likelihood. The Bayesian 2DMC method performs poorly, with coverage probabilities both for the linear and quadratic dose coefficients that are under 5%, particularly when the magnitudes of classical and Berkson error are both moderate to large (20%-50%). The method also produces substantially biased (by a factor of 10) estimates of both the linear and quadratic coefficients, with the linear coefficient overestimated and the quadratic coefficient underestimated. By comparison the extended regression calibration method yields coverage probabilities that are too low when shared and unshared Berkson errors are both large (50%), although otherwise it performs well, and coverage is generally better than the Bayesian 2DMC and all other methods. The bias of the predicted relative risk at a variety of doses is generally smallest for extended regression calibration, and largest for the Bayesian 2DMC method (apart from unadjusted regression), with standard regression calibration and Monte Carlo maximum likelihood exhibiting bias in predicted relative risk generally somewhat intermediate between the other two methods.

Risk of hematological malignancies from CT radiation exposure in children, adolescents and young adults

Over one million European children undergo computed tomography (CT) scans annually. Although moderate- to high-dose ionizing radiation exposure is an established risk factor for hematological malignancies, risks at CT examination dose levels remain uncertain. Here we followed up a multinational cohort (EPI-CT) of 948,174 individuals who underwent CT examinations before age 22 years in nine European countries. Radiation doses to the active bone marrow were estimated on the basis of body part scanned, patient characteristics, time period and inferred CT technical parameters. We found an association between cumulative dose and risk of all hematological malignancies, with an excess relative risk of 1.96 (95% confidence interval 1.10 to 3.12) per 100 mGy (790 cases). Similar estimates were obtained for lymphoid and myeloid malignancies. Results suggest that for every 10,000 children examined today (mean dose 8 mGy), 1-2 persons are expected to develop a hematological malignancy attributable to radiation exposure in the subsequent 12 years. Our results strengthen the body of evidence of increased cancer risk at low radiation doses and highlight the need for continued justification of pediatric CT examinations and optimization of doses.

Second Primary Malignancy After Radioiodine Therapy in Thyroid Cancer Patient: A Nationwide Study

Objective

This study aimed to investigate the risk of second primary malignancy after radioiodine (RAI) therapy in patients with thyroid cancer, using the National Health Insurance Service (NHIS) database.

Methods

We extracted data from the NHIS database of South Korea, which covers the entire population of the nation. Risk of second primary malignancy in the thyroid cancer patients who received RAI therapy were compared with the thyroid cancer patients who received surgery only.

Results

Between January 1, 2004, and December 31, 2018, we identified 363,155 patients who underwent thyroid surgery due to thyroid cancer for analysis. The surgery only cohort was 215,481, and the RAI cohort was 147,674 patients. A total of 19,385 patients developed second primary malignancy (solid cancer, 18,285; hematologic cancer, 1,100). There was no significant increase in the risk of second primary malignancy in patients who received a total cumulative dose of 100 mCi or less (hazard ratio [HR], 1.013; 95% confidence interval [CI], 0.979-1.049). However, a statistically significant increase in the risk of second primary malignancy was observed in patients who received 101-200 mCi (HR, 1.214; 95% CI, 1.167-1.264), 201-300 mCi (HR, 1.422; 95% CI, 1.258-1.607), and > 300 mCi (HR, 1.693; 95% CI, 1.545-1.854).

Conclusion

Total cumulative doses of 100 mCi or less of RAI can be safely administered without concerns about second primary malignancy. However, the risk of second primary malignancy increases in a dose-dependent manner, and the risk-benefit needs to be considered for doses over 100 mCi of RAI therapy.

Therapy-Related Myeloid Neoplasms: Predisposition and Clonal Evolution

Therapy-related Myeloid Neoplasm (t-MN) represents one of the worst long-term consequences of cytotoxic therapy for primary tumors and autoimmune disease. Poor survival and refractoriness to current treatment strategies characterize affected patients from a clinical point of view. In our aging societies, where newer therapies and ameliorated cancer management protocols are improving the life expectancy of cancer patients, therapy-related Myeloid Neoplasms are an emerging problem. Although several research groups have contributed to characterizing the main risk factors in t-MN development, the multiplicity of primary tumors, in association with the different therapeutic strategies available and the new drugs in development, make interpreting the current data still complex. The main risk factors involved in t-MN pathogenesis can be subgrouped into patient-specific, inherited, and acquired predispositions. Although t-MN can occur at any age, the risk tends to increase with advancing age, and older patients, characterized by a higher number of comorbidities, are more likely to develop the disease. Thanks to the availability of deep sequencing techniques, germline variants have been reported in 15-20% of t-MN patients, highlighting their role in cancer predisposition. It is becoming increasingly evident that t-MN with driver gene mutations may arise in the background of Clonal Hematopoiesis of Indeterminate Potential (CHIP) under the positive selective pressure of chemo and/or radiation therapies. Although CHIP is generally considered benign, it has been associated with an increased risk of t-MN. In this context, the phenomenon of clonal evolution may be described as a dynamic process of expansion of preexisting clones, with or without acquisition of additional genetic alterations, that, by favoring the proliferation of more aggressive and/or resistant clones, may play a crucial role in the progression from preleukemic states to t-MN.

Impact of proton therapy on the DNA damage induction and repair in hematopoietic stem and progenitor cells

Proton therapy is of great interest to pediatric cancer patients because of its optimal depth dose distribution. In view of healthy tissue damage and the increased risk of secondary cancers, we investigated DNA damage induction and repair of radiosensitive hematopoietic stem and progenitor cells (HSPCs) exposed to therapeutic proton and photon irradiation due to their role in radiation-induced leukemia. Human CD34+ HSPCs were exposed to 6 MV X-rays, mid- and distal spread-out Bragg peak (SOBP) protons at doses ranging from 0.5 to 2 Gy. Persistent chromosomal damage was assessed with the micronucleus assay, while DNA damage induction and repair were analyzed with the γ-H2AX foci assay. No differences were found in induction and disappearance of γ-H2AX foci between 6 MV X-rays, mid- and distal SOBP protons at 1 Gy. A significantly higher number of micronuclei was found for distal SOBP protons compared to 6 MV X-rays and mid- SOBP protons at 0.5 and 1 Gy, while no significant differences in micronuclei were found at 2 Gy. In HSPCs, mid-SOBP protons are as damaging as conventional X-rays. Distal SOBP protons showed a higher number of micronuclei in HSPCs depending on the radiation dose, indicating possible changes of the in vivo biological response.

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.

Modeling and countering the effects of cosmic radiation using bioengineered human tissues

Cosmic radiation is the most serious risk that will be encountered during the planned missions to the Moon and Mars. There is a compelling need to understand the effects, safety thresholds, and mechanisms of radiation damage in human tissues, in order to develop measures for radiation protection during extended space travel. As animal models fail to recapitulate the molecular changes in astronauts, engineered human tissues and "organs-on-chips" are valuable tools for studying effects of radiation in vitro. We have developed a bioengineered tissue platform for studying radiation damage in individualized settings. To demonstrate its utility, we determined the effects of radiation using engineered models of two human tissues known to be radiosensitive: engineered cardiac tissues (eCT, a target of chronic radiation damage) and engineered bone marrow (eBM, a target of acute radiation damage). We report the effects of high-dose neutrons, a proxy for simulated galactic cosmic rays, on the expression of key genes implicated in tissue responses to ionizing radiation, phenotypic and functional changes in both tissues, and proof-of-principle application of radioprotective agents. We further determined the extent of inflammatory, oxidative stress, and matrix remodeling gene expression changes, and found that these changes were associated with an early hypertrophic phenotype in eCT and myeloid skewing in eBM. We propose that individualized models of human tissues have potential to provide insights into the effects and mechanisms of radiation during deep-space missions and allow testing of radioprotective measures.

Spi1 R235C point mutation confers hypersensitivity to radiation-induced acute myeloid leukemia in mice

Ionizing radiation (IR) is a risk factor for acute myeloid leukemia (rAML). Murine rAMLs feature both hemizygous chromosome 2 deletions (Del2) and point mutations (R235) within the hematopoietic regulatory gene Spi1. We generated a heterozygous CBA Spi1 R235 mouse (CBASpm/+) which develops de novo AML with 100% incidence by ∼12 months old and shows a dose-dependent reduction in latency following X-irradiation. These effects are reduced on an AML-resistant C57Bl6 genetic background. CBASpm/Gfp reporter mice show increased Gfp expression, indicating compensation for Spm-induced Spi1 haploinsufficiency. Del2 is always detected in both de novo and rAMLs, indicating that biallelic Spi1 mutation is required for AML. CBASpm/+ mice show that a single Spm modification is sufficient for initiating AML development with complete penetrance, via the "two-hit" mechanism and this is accelerated by IR exposure. Similar SPI1/PU.1 polymorphisms in humans could potentially lead to enhanced susceptibility to IR following medical or environmental exposure.

A generalisation of the method of regression calibration

There is direct evidence of risks at moderate and high levels of radiation dose for highly radiogenic cancers such as leukaemia and thyroid cancer. For many cancer sites, however, it is necessary to assess risks via extrapolation from groups exposed at moderate and high levels of dose, about which there are substantial uncertainties. Crucial to the resolution of this area of uncertainty is the modelling of the dose-response relationship and the importance of both systematic and random dosimetric errors for analyses in the various exposed groups. It is well recognised that measurement error can alter substantially the shape of this relationship and hence the derived population risk estimates. Particular attention has been devoted to the issue of shared errors, common in many datasets, and particularly important in occupational settings. We propose a modification of the regression calibration method which is particularly suited to studies in which there is a substantial amount of shared error, and in which there may also be curvature in the true dose response. This method can be used in settings where there is a mixture of Berkson and classical error. In fits to synthetic datasets in which there is substantial upward curvature in the true dose response, and varying (and sometimes substantial) amounts of classical and Berkson error, we show that the coverage probabilities of all methods for the linear coefficient [Formula: see text] are near the desired level, irrespective of the magnitudes of assumed Berkson and classical error, whether shared or unshared. However, the coverage probabilities for the quadratic coefficient [Formula: see text] are generally too low for the unadjusted and regression calibration methods, particularly for larger magnitudes of the Berkson error, whether this is shared or unshared. In contrast Monte Carlo maximum likelihood yields coverage probabilities for [Formula: see text] that are uniformly too high. The extended regression calibration method yields coverage probabilities that are too low when shared and unshared Berkson errors are both large, although otherwise it performs well, and coverage is generally better than these other three methods. A notable feature is that for all methods apart from extended regression calibration the estimates of the quadratic coefficient [Formula: see text] are substantially upwardly biased.

A generalisation of the method of regression calibration

There is direct evidence of risks at moderate and high levels of radiation dose for highly radiogenic cancers such as leukaemia and thyroid cancer. For many cancer sites, however, it is necessary to assess risks via extrapolation from groups exposed at moderate and high levels of dose, about which there are substantial uncertainties. Crucial to the resolution of this area of uncertainty is the modelling of the dose-response relationship and the importance of both systematic and random dosimetric errors for analyses in the various exposed groups. It is well recognised that measurement error can alter substantially the shape of this relationship and hence the derived population risk estimates. Particular attention has been devoted to the issue of shared errors, common in many datasets, and particularly important in occupational settings. We propose a modification of the regression calibration method which is particularly suited to studies in which there is a substantial amount of shared error, and in which there may also be curvature in the true dose response. This method can be used in settings where there is a mixture of Berkson and classical error. In fits to synthetic datasets in which there is substantial upward curvature in the true dose response, and varying (and sometimes substantial) amounts of classical and Berkson error, we show that the coverage probabilities of all methods for the linear coefficient \(\alpha\) are near the desired level, irrespective of the magnitudes of assumed Berkson and classical error, whether shared or unshared. However, the coverage probabilities for the quadratic coefficient \(\beta\) are generally too low for the unadjusted and regression calibration methods, particularly for larger magnitudes of the Berkson error, whether this is shared or unshared. In contrast Monte Carlo maximum likelihood yields coverage probabilities for \(\beta\) that are uniformly too high. The extended regression calibration method yields coverage probabilities that are too low when shared and unshared Berkson errors are both large, although otherwise it performs well, and coverage is generally better than these other three methods. A notable feature is that for all methods apart from extended regression calibration the estimates of the quadratic coefficient \(\beta\) are substantially upwardly biased.

Noncancer Effects of Ionizing Radiation Exposure on the Eye, the Circulatory System and beyond: Developments made since the 2011 ICRP Statement on Tissue Reactions

For radiation protection purposes, noncancer effects with a threshold-type dose-response relationship have been classified as tissue reactions (formerly called nonstochastic or deterministic effects), and equivalent dose limits aim to prevent occurrence of such tissue reactions. Accumulating evidence demonstrates increased risks for several late occurring noncancer effects at doses and dose rates much lower than previously considered. In 2011, the International Commission on Radiological Protection (ICRP) issued a statement on tissue reactions to recommend a threshold of 0.5 Gy to the lens of the eye for cataracts and to the heart and brain for diseases of the circulatory system (DCS), independent of dose rate. Literature published thereafter continues to provide updated knowledge. Increased risks for cataracts below 0.5 Gy have been reported in several cohorts (e.g., including in those receiving protracted or chronic exposures). A dose threshold for cataracts is less evident with longer follow-up, with limited evidence available for risk of cataract removal surgery. There is emerging evidence for risk of normal-tension glaucoma and diabetic retinopathy, but the long-held tenet that the lens represents among the most radiosensitive tissues in the eye and in the body seems to remain unchanged. For DCS, increased risks have been reported in various cohorts, but the existence or otherwise of a dose threshold is unclear. The level of risk is less uncertain at lower dose and lower dose rate, with the possibility that risk per unit dose is greater at lower doses and dose rates. Target organs and tissues for DCS are also unknown, but may include heart, large blood vessels and kidneys. Identification of potential factors (e.g., sex, age, lifestyle factors, coexposures, comorbidities, genetics and epigenetics) that may modify radiation risk of cataracts and DCS would be important. Other noncancer effects on the radar include neurological effects (e.g., Parkinson's disease, Alzheimer's disease and dementia) of which elevated risk has increasingly been reported. These late occurring noncancer effects tend to deviate from the definition of tissue reactions, necessitating more scientific developments to reconsider the radiation effect classification system and risk management. This paper gives an overview of historical developments made in ICRP prior to the 2011 statement and an update on relevant developments made since the 2011 ICRP statement.

Low-Dose Non-Targeted Effects and Mitochondrial Control

Non-targeted effects (NTE) have been generally regarded as a low-dose ionizing radiation (IR) phenomenon. Recently, regarding long distant abscopal effects have also been observed at high doses of IR) relevant to antitumor radiation therapy. IR is inducing NTE involving intracellular and extracellular signaling, which may lead to short-ranging bystander effects and distant long-ranging extracellular signaling abscopal effects. Internal and "spontaneous" cellular stress is mostly due to metabolic oxidative stress involving mitochondrial energy production (ATP) through oxidative phosphorylation and/or anaerobic pathways accompanied by the leakage of O₂^- and other radicals from mitochondria during normal or increased cellular energy requirements or to mitochondrial dysfunction. Among external stressors, ionizing radiation (IR) has been shown to very rapidly perturb mitochondrial functions, leading to increased energy supply demands and to ROS/NOS production. Depending on the dose, this affects all types of cell constituents, including DNA, RNA, amino acids, proteins, and membranes, perturbing normal inner cell organization and function, and forcing cells to reorganize the intracellular metabolism and the network of organelles. The reorganization implies intracellular cytoplasmic-nuclear shuttling of important proteins, activation of autophagy, and mitophagy, as well as induction of cell cycle arrest, DNA repair, apoptosis, and senescence. It also includes reprogramming of mitochondrial metabolism as well as genetic and epigenetic control of the expression of genes and proteins in order to ensure cell and tissue survival. At low doses of IR, directly irradiated cells may already exert non-targeted effects (NTE) involving the release of molecular mediators, such as radicals, cytokines, DNA fragments, small RNAs, and proteins (sometimes in the form of extracellular vehicles or exosomes), which can induce damage of unirradiated neighboring bystander or distant (abscopal) cells as well as immune responses. Such non-targeted effects (NTE) are contributing to low-dose phenomena, such as hormesis, adaptive responses, low-dose hypersensitivity, and genomic instability, and they are also promoting suppression and/or activation of immune cells. All of these are parts of the main defense systems of cells and tissues, including IR-induced innate and adaptive immune responses. The present review is focused on the prominent role of mitochondria in these processes, which are determinants of cell survival and anti-tumor RT.

Lympho-hematopoietic malignancies risk after exposure to low dose ionizing radiation during cardiac catheterization in childhood

Pediatric patients with congenital heart disease (CHD) often undergo low dose ionizing radiation (LDIR) from cardiac catheterization (CC) for the diagnosis and/or treatment of their disease. Although radiation doses from a single CC are usually low, less is known about the long-term radiation associated cancer risks. We aimed to assess the risk of lympho-hematopoietic malignancies in pediatric CHD patients diagnosed or treated with CC. A French cohort of 17,104 children free of cancer who had undergone a first CC from 01/01/2000 to 31/12/2013, before the age of 16 was set up. The follow-up started at the date of the first recorded CC until the exit date, i.e., the date of death, the date of first cancer diagnosis, the date of the 18th birthday, or the 31/12/2015, whichever occurred first. Poisson regression was used to estimate the LDIR associated cancer risk. The median follow-up was 5.9 years, with 110,335 person-years. There were 22,227 CC procedures, yielding an individual active bone marrow (ABM) mean cumulative dose of 3.0 milligray (mGy). Thirty-eight incident lympho-hematopoietic malignancies were observed. When adjusting for attained age, gender and predisposing factors to cancer status, no increased risk was observed for lympho-hematopoietic malignancies RR/mGy = 1.00 (95% CI: 0.88; 1.10). In summary, the risk of lympho-hematopoietic malignancies and lymphoma was not associated to LDIR in pediatric patients with CHD who undergo CC. Further epidemiological studies with greater statistical power are needed to improve the assessment of the dose-risk relationship.

The scientific basis for the use of the linear no-threshold (LNT) model at low doses and dose rates in radiological protection

The linear no-threshold (LNT) model was introduced into the radiological protection system about 60 years ago, but this model and its use in radiation protection are still debated today. This article presents an overview of results on effects of exposure to low linear-energy-transfer radiation in radiobiology and epidemiology accumulated over the last decade and discusses their impact on the use of the LNT model in the assessment of radiation-related cancer risks at low doses. The knowledge acquired over the past 10 years, both in radiobiology and epidemiology, has reinforced scientific knowledge about cancer risks at low doses. In radiobiology, although certain mechanisms do not support linearity, the early stages of carcinogenesis comprised of mutational events, which are assumed to play a key role in carcinogenesis, show linear responses to doses from as low as 10 mGy. The impact of non-mutational mechanisms on the risk of radiation-related cancer at low doses is currently difficult to assess. In epidemiology, the results show excess cancer risks at dose levels of 100 mGy or less. While some recent results indicate non-linear dose relationships for some cancers, overall, the LNT model does not substantially overestimate the risks at low doses. Recent results, in radiobiology or in epidemiology, suggest that a dose threshold, if any, could not be greater than a few tens of mGy. The scientific knowledge currently available does not contradict the use of the LNT model for the assessment of radiation-related cancer risks within the radiological protection system, and no other dose-risk relationship seems more appropriate for radiological protection purposes.

Radon-222 and Leukemia

ABSTRACT

Leukemia was the first medically observed human cancer related to ionizing radiation in the 1945 follow-up study of atomic bomb survivors. The bone exposure and dose calculated here are based on the measured solubility of the noble gas 222 Rn in blood. A fraction of the 222 Rn gas in blood distributes as dissolved gas to all organs, with the fraction depending upon the blood flow rate to the organ. The exposure and dose calculated are for men and women based on measurements made for the blood flow rate to the femur, the largest bone in the human skeleton. The annual exposure and dose estimated for continuous 222 Rn inhalation of 100 Bq m -3 are very low and unlikely to cause leukemia. Other neurological issues, from lifetime exposure to low activity concentrations of 222 Rn alpha particle exposure in bone, are unknown.