Studies of the mortality of atomic bomb survivors, Report 14, 1950-2003: an overview of cancer and noncancer diseases

Modulating systemic anti-inflammatory response mitigates osteoarthritis progression and associated pain after low-dose radiotherapy

Osteoarthritis (OA) is a degenerative joint disease, often accompanied by inflammation. It has reported that low-dose radiotherapy (LDRT) has anti-inflammatory effect for benign pathologies and has been used for clinical treatment of OA in some European regions. However, the underlying molecular mechanisms of LDRT alleviating OA are only poorly understood. Herein, it is verified that LDRT improved the locomotor ability of OA rats, increased the locomotor distance and speed in the in vivo experiments. Moreover, LDRT decreased the degree of cartilage damage, attenuated the synovial inflammation, and promoted macrophage polarization towards M2 type. For the in vitro experiments, LDRT promoted macrophage polarization towards M2-type, which enhanced cell growth and adjusted the inflammatory factors in chondrocyte. Additionally, it is found LDRT could ameliorate OA pain through inhibiting spinal cord inflammation. Take together, our study suggests that LDRT could ameliorate OA symptoms and relieve OA-related pain by exerting its anti-inflammatory effect.

Identifying radiation-induced symptoms from an interview survey

Studies on the atomic bomb have reported a relatively high incidence of acute symptoms, even at below the threshold dose of radiation, and are therefore assumed to include symptoms caused by non-radiation factors. In this study, to investigate the influence of external injuries and burns on symptom expression and the possibility of distinguishing radiation-induced symptoms, we reanalysed data from the survey conducted immediately after the atomic bombing of Nagasaki. The adjusted odds ratios (ORs) of radiation per 1 Gy for the occurrence of 16 symptoms ranged from 1.14 to 1.46, based on sex, age at the time of the bombing, radiation dose, external injuries, and burns. This study also included 243 deaths, and thus provides information not seen in other studies, such as the frequency of symptoms in deaths and ORs for symptom occurrence. However, the adjusted ORs for external injuries or burns were smaller than the unadjusted ORs, suggesting that external injuries and burns confound the development of radiation-induced symptoms. Symptom data obtained from interviews such as those used in this study may not be appropriate for use alone because such data include non-radiation factors. Radiation-induced symptoms are often considered to be a syndrome, and the multiple correspondence analyses also revealed that high-dose exposure is associated with nausea and vomiting, subsequent epilation and bleeding tendency as a bone marrow disorder, and inflammation symptoms due to a weakened immune system. Thus, radiation exposure may be indicated by not just one, but rather, a combination of symptoms.

Site-specific cancer mortality after low-level exposure to ionizing radiation: findings from an update of the International Nuclear Workers Study (INWORKS)

A major update to the International Nuclear Workers Study was undertaken that allows us to report updated estimates of associations between radiation and site-specific solid cancer mortality. A cohort of 309 932 nuclear workers employed in France, the United Kingdom, and the United States were monitored for external radiation exposure. Associations of radiation with cancer mortality were quantified as the excess relative rate (ERR) per gray (Gy) using a maximum likelihood and a Markov chain Monte Carlo method (to stabilize estimates via a hierarchical regression). The analysis included 28 089 deaths due to solid cancer, the most common being lung, prostate, and colon cancer. Using maximum likelihood, positive estimates of ERR per Gy were obtained for stomach, colon, rectum, pancreas, peritoneum, larynx, lung, pleura/mesothelioma, bone and connective tissue, skin, prostate, testis, bladder, kidney, thyroid, and residual cancers. Negative estimates of ERR per Gy were found cancers of oral cavity and pharynx, esophagus, and ovary. A hierarchical model stabilized site-specific estimates of association, including for lung (ERR per Gy = 0.65; 95% credible interval [CrI], 0.24-1.07), prostate (ERR per Gy = 0.44; 95% CrI, -0.06 to 0.91), and colon cancer (ERR per Gy = 0.53; 95% CrI, -0.07 to 1.11). The results contribute evidence regarding associations between low-dose radiation and cancer.

Colossus: software for radiation epidemiological studies with big data

Colossus is designed to meet a growing need for survival analysis software capable of analyzing tens of millions of rows of radiation epidemiological data. Colossus is an R package devised to offer scalable survival analysis for the Million Person Study. The total and relative rate equations available in Colossus are outlined in this article, which are used in conjunction with Cox proportional hazards, Poisson, and Fine-Grey regression models. Following a comparison with existing software, validation with epidemiological cohort data is described. Exposure data and specific causes of death among workers at Los Alamos National Laboratory and U.S. nuclear power plants were analyzed by Colossus and 32-bit Epicure and compared with published results. Colossus results agreed with the results of existing software and previous publications.

The role of polysaccharide POM extracted from Pleurotus ostreatus in curbing and treating the harmful effects on liver and kidney resulting from radiation exposure

PURPOSE

This research assesses the radioprotective and antioxidant activity of polysaccharide (POM) derived from Pleurotus ostreatus strain on rats suffering from metabolic problems due to irradiation. The crude POM obtained through chemical analysis was found to consist of glucose, galactose, and fructose in 1:1.2:0.1 ratio but was absent of uronic acid, and sulfate. Moreover, it demonstrated radical scavenging activity (45.21-84.21%) at 5 mg/ml concentration.

METHODS

A total of thirty-two male Sprague-Dawley rats were used and split into four groups: control, radiation (whole body RT with 5 Gy gamma rays), POM treatment (28 days at 100 mg/kg body weight), POM + radiation (n = 8 rats/group). Monitoring of body weight was done and on day 28, cardiac blood samples were collected and tested on liver and kidney function indices. ELISA was used to test for inflammatory factors and liver and kidney sections were stained with hematoyxlin-eosin, and other tests for DNA fragmentation were undertaken.

RESULTS

The rats that underwent radiation exhibited reduced body weights, metabolic disruption, and decrease in antioxidant enzyme activities. The histological analysis displayed edema of hepatic cells, inflammatory cell infiltration, and vacuolar degeneration. On the other hand, rats in the POM + Radiation group showed less severe pathological changes. POM treated rats had restored their liver and kidney functions, lower TBARS, higher total protein, and improved antioxidant enzyme activities.

CONCLUSION

POM treatment effectively alleviates liver and kidney damage caused by radiation exposure.

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.

Radiation exposure in neurosurgical intensive care unit patients: Balancing diagnostic benefits and long-term risks

BACKGROUND

X-ray, computed tomography (CT), and digital subtraction angiography (DSA) techniques are indispensable in managing critically ill neurosurgical patients. However, repeated diagnostic imaging leads to cumulative radiation exposure, raising concerns about long-term risks such as malignancies. This study evaluates the frequency, dosage, and implications of radiation exposure in a neurosurgical intensive care unit (NICU) patient cohort.

METHODS

A retrospective analysis was conducted on 589 patients admitted to the NICU between 2013 and 2018 with the diagnosis of traumatic brain injury (TBI), intracerebral hemorrhage (ICH), subarachnoidal hemorrhage (SAH), and stroke with >24 h of mechanical ventilation time. The cumulative radiation dose per patient from X-ray, CT, and DSA imaging was calculated and stratified by diagnostic indication, patient condition, and clinical course. To contextualize the findings, international benchmarks were compared.

RESULTS

The cohort's median cumulative effective dose (ED) was 17.8 mSv (range: 1.7-194.3 mSv). CT scans accounted for 81.95 % of the total radiation exposure, with head and thorax imaging being the most frequently performed studies. Younger age and a shorter ventilation time revealed a significant increase in the calculated lifetime attributable risk (LAR) of radiation-induced cancer in multivariate testing. Comparisons with international data revealed a comparable level of radiation exposure in this cohort. Despite the high radiation burden, imaging was deemed clinically essential, with direct implications for patient outcomes.

CONCLUSION

While radiation exposure in NICU patients is substantial, the benefits of timely and accurate diagnostic information outweigh the potential long-term risks. In critical care settings, where patients face life-threatening conditions, the judicious use of diagnostic imaging is essential. Future efforts should focus on optimizing imaging protocols to minimize radiation exposure without compromising diagnostic quality.

Analysis of Departures from Linearity in the Dose Response for Japanese Atomic Bomb Survivor Solid Cancer Mortality and Cancer Incidence Data and Assessment of Low-Dose Extrapolation Factors

Although leukemia in the Japanese atomic bomb survivor data has long exhibited upward curvature, until recently this appeared not to be the case for solid cancer. It has been suggested that the recently observed upward curvature in the dose response for the Japanese atomic bomb survivor solid cancer mortality data may be accounted for by flattening of the dose response in the moderate dose range (0.3-0.7 Gy). To investigate this, the latest version available of the solid cancer mortality and incidence datasets (with follow-up over the years 1950-2003 and 1958-2009 respectively) for the Life Span Study cohort of atomic bomb survivors was used to assess possible departures from linearity in the moderate dose range. Linear-spline models were fitted, also up to 6th order polynomial models in dose (higher order polynomials tended not to converge). The organ dose used for all solid cancers was weighted dose to the colon. There are modest indications of departures from linearity for the mortality data, whether using polynomial or linear-spline models. Use of the Akaike information criterion (AIC) suggests that the optimal model for the mortality data is given by a 5th order polynomial in dose. There is borderline significant (P = 0.071) indication of improvement provided by a linear-spline model in the mortality data. The low-dose extrapolation factor (LDEF), which measures the degree of overestimation of low-dose linear slope by the linear slope fitted over some specified dose range, is generally between 1.1-2.0 depending on the dose range, with upper confidence limits that sometimes exceed 10; although LDEF < 1 for the lowest dose range (<0.5 Gy), there are substantial uncertainties, with an upper confidence limit that exceeds 1.6. There are generally only modest indications of departures from linearity for the solid cancer incidence data, whether using polynomial or linear-spline models. In contrast to the mortality data, there are much weaker indications of improvement in fit provided by higher order polynomials, and only weak indications (P > 0.2) of improvement provided by linear-spline models. Nevertheless, use of AIC suggests that the optimal model for the incidence data is given by a 3rd order polynomial. LDEF evaluated over various dose ranges is generally between 1.2-1.4 with upper confidence limits that generally exceed 1.6; although LDEF < 1 for the lowest dose range (<0.5 Gy), there are substantial uncertainties, with an upper confidence limit that substantially exceeds 2.0. In summary, the evidence we have presented for higher order powers than the second in the dose response is not overwhelmingly strong, and is to some extent dependent on dose range. A feature of the dose response, which is reflected in the higher-order polynomials fitted to the data, is a leveling off or even a downturn in the response at doses >2 Gy. The linear-quadratic model is very widely used for modeling of dose response, and has been widely used in radiotherapy oncology applications as part of treatment planning. There is a theoretical basis for this model, based on the two-target model, although the data used to validate this has been mainly in vitro; there may be more complicated interactions than are implied by a two-target model, but the contributions made by these, which would contribute to higher order (than quadratic) powers of dose, may not be very pronounced over moderate ranges of dose.

Super-competition as a Novel Mechanism of the Dose-rate Effect in Radiation Carcinogenesis: A Mathematical Model Study

Data from animal experiments show that the radiation-related risk of cancer decreases if the dose rate is reduced, even though the cumulative dose is unchanged (i.e., a dose-rate effect); however, the underlying mechanism is not well understood. To explore factors underlying the dose-rate effect observed in experimental rat mammary carcinogenesis, we developed a mathematical model that accounts for cellular dynamics during carcinogenesis, and then examined whether the model predicts cancer incidence. A mathematical model of multistage carcinogenesis involving radiation-induced cell death and mutagenesis was constructed using differential equations. The mutation rate was changed depending on the dose rate. The model also considered competition among cells with various mutation levels. The main parameters of the model were determined using previous experimental data. The parameters of the model were consistent with experimental observations. A dose-rate effect on carcinogenesis became apparent when the relationship between dose rate and mutation rate was linear quadratic or quadratic. The dose-rate effect became prominent when cells with more mutations preferentially compensated for the radiation-induced death of cells with fewer mutations. The phenomenon by which mutated cells gain a competitive advantage over normal cells is known as super-competition. Here, we identified super-competition as a novel mechanism underlying the dose-rate effects on carcinogenesis. The data also confirmed the relevance of the shape of the relationship between dose rate and the mutation rate. Thus, this study provides new evidence for the mechanism underlying the dose-rate effect, which is important for predicting the cancer-related risks of low-dose-rate irradiation.

An examination of the dose rate effect in mice assuming that the carcinogenic effect of radiation is life shortening resulting from a tissue reaction

PURPOSE

Radiation exposures do not seem to increase the proportion of mice dying from tumors, but rather cause a shift in the appearance of spontaneous cancers, allowing them to appear earlier, and hence produce a life shortening effect. Then, it was possible to estimate the effect of the dose rate on the carcinogenic effects of radiation using life shortening effects as a measure.

CONCLUSION

The dose response for the induction of life shortening was linear under acute exposure conditions, which indicates that the response under chronic exposure conditions is also likely to be linear, and hence the dose rate factor (DRF) would be constant throughout the dose. Furthermore, the life shortening effect decreased sharply with an increase in age at exposure. To separate the dose rate effect from the effects of age under long-term exposure conditions, a thought experiment was designed which consisted of 8 repeated exposures to an acute 1 Gy dose at intervals of 50 days with an assumption that the effect is additive, and the results were compared with those observed in a chronic continuous exposure experiment (20 mGy per day for 400 days, for a total of 8 Gy: Tanaka et al. 2003). The results showed 211 days of life shortening in the former and 120 days in the latter, which provided a DRF of 1.8 (211/120). If one assumes that a tissue reaction is the primary cause of radiation carcinogenesis, the contrasting two concepts, radiation hormesis and linear-non-threshold model at low doses, would become compatible.

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.

Hepatic Stellate Cell-mediated Increase in CCL5 Chemokine Expression after X-ray Irradiation Determined In Vitro and In Vivo

Radiation exposure causes hepatitis which induces hepatic steatosis and fibrosis. Although hepatic stellate cells (HSCs) have been considered potential pathological modulators for the development of hepatitis due to viral and microbial infections, their involvement in radiation-induced hepatitis is yet to be determined. This study aimed to clarify the relationship between radiation exposure and expressions of inflammatory cytokines and chemokines in HSCs in vitro and in vivo. HSCs were obtained from 1-week-old mice, known to be highly sensitive to radiation-induced hepatocellular carcinoma, using a newly established method combining liver perfusion, cell dissociation, and density gradient centrifugation, followed by magnetic negative selection of hematopoietic and endothelial cells with anti-CD45.2 and CD146 antibodies. The isolated HSCs were confirmed by the expression of desmin and glial fibrillary acidic protein (GFAP). We demonstrated that primary cultured HSCs, exposed to X-ray irradiation (0, 1.9, and 3.8 Gy) and cultured for 3 and 7 days, produced elevated levels of C-C motif chemokine ligand 5 (CCL5, also known as RANTES) inflammatory chemokine in a dose-dependent manner. An in vivo immunofluorescence method confirmed that increased CCL5 signals were observed in GFAP-positive HSCs in mouse livers 7 days after whole-body X-ray irradiation (1.9 and 3.8 Gy). Adequate expression of C-C motif chemokine receptor 5 (Ccr5), a receptor for CCL5, was also detected using real-time PCR in the liver of both irradiated and non-irradiated mice. Taken together, our data suggest that HSCs may drive hepatitis via CCL5/CCR5 axis in the liver under radiation-induced stress. Furthermore, this newly established experimental protocol can help evaluate the expression of other inflammatory cytokines in primary cultures of HSCs isolated from infant mice.

Mitochondrial reactive oxygen species-mediated fibroblast activation has a role in tumor microenvironment formation in radiation carcinogenesis

Cancer risks attributable to low-dose and low-dose-rate radiation are a serious concern for public health. Radiation risk assessment is based on lifespan studies among Hiroshima-Nagasaki A-bomb survivors; however, there are statistical limitations due to a small sample size for low-dose radiation. Therefore, basic biological studies are helpful in understanding the mechanism of radiation carcinogenesis. The detrimental effects of ionising radiation (IR) are caused by reactive oxygen species (ROS)-mediated oxidative DNA damage. IR-induced delayed ROS are produced in the electron transport chain reaction of the mitochondrial complex. Thus, mitochondria are a source of ROS and a primary target for ROS attacks. Consequently, mitochondrial dysfunction is thought to be a key event in the metabolic changes of cancer cells and is important in radiation-induced carcinogenesis. In this paper, we present recent findings on radiation carcinogenesis effect assessment, focusing on mitochondrial function as stress sensors.

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.

Low-dose radiation promotes high-fat diet-induced atherosclerosis by activating cGAS signal pathway

BACKGROUND

Atherosclerosis (AS) is the most prevalent cardiovascular disease, with an exceptionally high burden. High-fat diet (HFD) is a popular diet behavior, whereas low-dose radiation (LDR) is an environmental physical factor. There is evidence to suggest that an HFD may exacerbate the onset of atherosclerosis. Whether the combination effect of HFD and LDR would have potential on atherosclerosis development remains incompletely unclear.

METHODS

In this study, ApoE-/- mice were used as atherosclerosis model animals to investigate the combination effects of HFD and LDR (10 × 0.01Gy, or 20 × 0.01Gy) on vascular lesions. Doppler ultrasound imaging, H&E staining, oil red O staining, western blotting, and immunohistochemistry (IHC) were used to assess the pro-atherosclerotic effects. LC-MS was used to detect the non-targeted lipidomic.

RESULTS

Long-term exposure of low-dose radiation at an accumulated dose of 0.2Gy significantly increased the occurrence of vascular stiffness and the aortic lesion in ApoE-/- mice. The synergistic effect of HFD and LDR was observed in the development of atherosclerosis, which might be linked to both the dysbiosis of lipid metabolism and the stimulation of the inflammatory signaling system. Moreover, LDR but not HFD can activate the cGAS-STING signaling through increasing the yield of cytosolic mitochondrial DNAs as well as the expression of cGAS protein. The activation of cGAS-STING signal triggers the release of IFN-α/-β, which functions as an inflammatory amplifier in the formation of atherosclerotic plaque.

CONCLUSION

The current study offers fresh insights into the risks and mechanism that underlie the development of atherosclerosis by LDR, and there is a combination effect of LDR and HFD with the involvement of cGAS-STING signal pathway.

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.

AOP report: Development of an adverse outcome pathway for deposition of energy leading to abnormal vascular remodeling

Cardiovascular diseases (CVDs) are complex, encompassing many types of heart pathophysiologies and associated etiologies. Radiotherapy studies have shown that fractionated radiation exposure at high doses (3-17 Gy) to the heart increases the incidence of CVD. However, the effects of low doses of radiation on the cardiovascular system or the effects from space travel, where radiation and microgravity are important contributors to damage, are not clearly understood. Herein, the adverse outcome pathway (AOP) framework was applied to develop an AOP to abnormal vascular remodeling from the deposition of energy. Following the creation of a preliminary pathway with the guidance of field experts and authoritative reviews, a scoping review was conducted that informed final key event (KE) selection and evaluation of the Bradford Hill criteria for the KE relationships (KERs). The AOP begins with a molecular initiating event of deposition of energy; ionization events increase oxidative stress, which when persistent concurrently causes the release of pro-inflammatory mediators, suppresses anti-inflammatory mechanisms and alters stress response signaling pathways. These KEs alter nitric oxide levels leading to endothelial dysfunction, and subsequent abnormal vascular remodeling (the adverse outcome). The work identifies evidence needed to strengthen understanding of the causal associations for the KERs, emphasizing where there are knowledge gaps and uncertainties in both qualitative and quantitative understanding. The AOP is anticipated to direct future research to better understand the effects of space on the human body and potentially develop countermeasures to better protect future space travelers.

Establishment and activity of the planning and acting network for low dose radiation research in Japan (PLANET): 2016-2023

The Planning and Acting Network for Low Dose Radiation Research in Japan (PLANET) was established in 2017 in response to the need for an all-Japan network of experts. It serves as an academic platform to propose strategies and facilitate collaboration to improve quantitative estimation of health risks from ionizing radiation at low-doses and low-dose-rates. PLANET established Working Group 1 (Dose-Rate Effects in Animal Experiments) to consolidate findings from animal experiments on dose-rate effects in carcinogenesis. Considering international trends in this field as well as the situation in Japan, PLANET updated its priority research areas for Japanese low-dose radiation research in 2023 to include (i) characterization of low-dose and low-dose-rate radiation risk, (ii) factors to be considered for individualization of radiation risk, (iii) biological mechanisms of low-dose and low-dose-rate radiation effects and (iv) integration of epidemiology and biology. In this context, PLANET established Working Group 2 (Dose and Dose-Rate Mapping for Radiation Risk Studies) to identify the range of doses and dose rates at which observable effects on different endpoints have been reported; Working Group 3 (Species- and Organ-Specific Dose-Rate Effects) to consider the relevance of stem cell dynamics in radiation carcinogenesis of different species and organs; and Working Group 4 (Research Mapping for Radiation-Related Carcinogenesis) to sort out relevant studies, including those on non-mutagenic effects, and to identify priority research areas. These PLANET activities will be used to improve the risk assessment and to contribute to the revision of the next main recommendations of the International Commission on Radiological Protection.

Luminal progenitor and mature cells are more susceptible than basal cells to radiation-induced DNA double-strand breaks in rat mammary tissue

Ionizing radiation promotes mammary carcinogenesis. Induction of DNA double-strand breaks (DSBs) is the initial event after radiation exposure, which can potentially lead to carcinogenesis, but the dynamics of DSB induction and repair are not well understood at the tissue level. In this study, we used female rats, which have been recognized as a useful experimental model for studying radiation effects on the mammary gland. We focused on differences in DSB kinetics among basal cells, luminal progenitor and mature cells in different parts of the mammary duct. 53BP1 foci were used as surrogate markers of DSBs, and 53BP1 foci in each mammary epithelial cell in immunostained tissue sections were counted 1-24 h after irradiation and fitted to an exponential function of time. Basal cells were identified as cytokeratin (CK) 14+ cells, luminal progenitor cells as CK8 + 18low cells and luminal mature cells as CK8 + 18high cells. The number of DSBs per nucleus tended to be higher in luminal cells than basal cells at 1 h post-irradiation. A model analysis indicated that basal cells in terminal end buds (TEBs), which constitute the leading edge of the mammary duct, had significantly fewer initial DSBs than the two types of luminal cells, and there was no significant difference in initial amount among the cell types in the subtending duct. The repair rate did not differ among mammary epithelial cell types or their locations. Thus, luminal progenitor and mature cells are more susceptible to radiation-induced DSBs than are basal cells in TEBs.

Age-Dependent Differences in Radiation-Induced DNA Damage Responses in Intestinal Stem Cells

Age at exposure is a critical modifier of the risk of radiation-induced cancer. However, the effects of age on radiation-induced carcinogenesis remain poorly understood. In this study, we focused on tissue stem cells using Lgr5-eGFP-ires-CreERT2 mice to compare radiation-induced DNA damage responses between Lgr5+ and Lgr5- intestinal stem cells. Three-dimensional immunostaining analyses demonstrated that radiation induced apoptosis and the mitotic index more efficiently in adult Lgr5- stem cells than in adult Lgr5+ stem cells but not in infants, regardless of Lgr5 expression. Supporting this evidence, rapid and transient p53 activation occurred after irradiation in adult intestinal crypts but not in infants. RNA sequencing revealed greater variability in gene expression in adult Lgr5+ stem cells than in infant Lgr5+ stem cells after irradiation. Notably, the cell cycle and DNA repair pathways were more enriched in adult stem cells than in infant stem cells after irradiation. Our findings suggest that radiation-induced DNA damage responses in mouse intestinal crypts differ between infants and adults, potentially contributing to the age-dependent susceptibility to radiation carcinogenesis.

Human-mouse comparison of the multistage nature of radiation carcinogenesis in a mathematical model

Mouse models are vital for assessing risk from environmental carcinogens, including ionizing radiation, yet the interspecies difference in the dose response precludes direct application of experimental evidence to humans. Herein, we take a mathematical approach to delineate the mechanism underlying the human-mouse difference in radiation-related cancer risk. We used a multistage carcinogenesis model assuming a mutational action of radiation to analyze previous data on cancer mortality in the Japanese atomic bomb survivors and in lifespan mouse experiments. Theoretically, the model predicted that exposure will chronologically shift the age-related increase in cancer risk forward by a period corresponding to the time in which the spontaneous mutational process generates the same mutational burden as that the exposure generates. This model appropriately fitted both human and mouse data and suggested a linear dose response for the time shift. The effect per dose decreased with increasing age at exposure similarly between humans and mice on a per-lifespan basis (0.72- and 0.71-fold, respectively, for every tenth lifetime). The time shift per dose was larger by two orders of magnitude in humans (7.8 and 0.046 years per Gy for humans and mice, respectively, when exposed at ~35% of their lifetime). The difference was mostly explained by the two orders of magnitude difference in spontaneous somatic mutation rates between the species plus the species-independent radiation-induced mutation rate. Thus, the findings delineate the mechanism underlying the interspecies difference in radiation-associated cancer mortality and may lead to the use of experimental evidence for risk prediction in humans.

Injectable Mechanophore Nanoparticles for Deep-Tissue Mechanochemical Dynamic Therapy

Photodynamic therapy (PDT) and sonodynamic therapy (SDT), using nonionizing light and ultrasound to generate reactive oxygen species, offer promising localized treatments for cancers. However, the effectiveness of PDT is hampered by inadequate tissue penetration, and SDT largely relies on pyrolysis and sonoluminescence, which may cause tissue injury and imprecise targeting. To address these issues, we have proposed a mechanochemical dynamic therapy (MDT) that uses free radicals generated from mechanophore-embedded polymers under mechanical stress to produce reactive oxygen species for cancer treatment. Yet, their application in vivo is constrained by the bulk form of the polymer and the need for high ultrasound intensities for activation. In this study, we developed injectable, nanoscale mechanophore particles with enhanced ultrasound sensitivity by leveraging a core-shell structure comprising silica nanoparticles (NPs) whose interfaces are linked to polymer brushes by an azo mechanophore moiety. Upon focused ultrasound (FUS) treatment, this injectable NP generates reactive oxygen species (ROS), demonstrating promising results in both an in vitro 4T1 cell model and an in vivo mouse model of orthotopic breast cancers. This research offers an alternative therapy technique, integrating force-responsive azo mechanophores and FUS under biocompatible conditions.

Risk of hematologic malignant neoplasms from head CT radiation in children and adolescents presenting with minor head trauma: a nationwide population-based cohort study

OBJECTIVES

The carcinogenic risks of CT radiation in children and adolescents remain debated. We aimed to assess the carcinogenic risk of CTs performed in children and adolescents with minor head trauma.

METHODS

In this nationwide population-based cohort study, we included 2,411,715 patients of age 0-19 with minor head trauma from 2009 to 2017. We excluded patients with elevated cancer risks or substantial past medical radiation exposure. Patients were categorized into CT-exposed or CT-unexposed group according to claim codes for head CT. The primary outcome was development of hematologic malignant neoplasms. Secondary outcomes included development of malignant solid neoplasms and benign neoplasms in the brain. We measured the incidence rate ratio (IRR) and incidence rate difference (IRD) using G-computation with Poisson regression adjusting for age, sex, hospital setting, and the type of head trauma.

RESULTS

Hematologic malignant neoplasms developed in 100 of 216,826 patients during 1,303,680 person-years in the CT-exposed group and in 808 of 2,194,889 patients during 13,501,227 person-years in the CT-unexposed group. For hematologic malignant neoplasms, the IRR was 1.29 (95% CI, 1.03-1.60) and the IRD was 1.71 (95% CI, 0.04-3.37) per 100,000 person-years at risk. The majority of excess hematologic malignant neoplasms were leukemia (IRR, 1.40 [98.3% CI, 1.05-1.87]; IRD, 1.59 [98.3% CI, 0.02-3.16] per 100,000 person-years at risk). There were no between-group differences for secondary outcomes.

CONCLUSIONS

Radiation exposure from head CTs in children and adolescents with minor head trauma was associated with an increased incidence of hematologic malignant neoplasms.

CLINICAL RELEVANCE STATEMENT

Our study provides a quantitative grasp of the risk conferred by CT examinations in children and adolescents, thereby providing the basis for cost-benefit analyses and evidence-driven guidelines for patient triaging in head trauma.

KEY POINTS

• This nationwide population-based cohort study showed that radiation exposure from head CTs in children and adolescents was associated with a higher incidence of hematologic malignant neoplasms. • The incidence rate of hematologic malignant neoplasms in the CT-exposed group was 29% higher than that in the CT-unexposed group (IRR, 1.29 [95% CI, 1.03-1.60]), and there were approximately 1.7 excess neoplasms per 100,000 person-years at risk in the CT-exposed group (IRD, 1.71 [0.04-3.37]). • Our study provides a quantified grasp of the risk conferred by CT examinations in children and adolescents, while controlling for biases observed in previous studies via specifying CT indication and excluding patients with predisposing conditions for cancer development.

Effect of Age at Time of Irradiation, Sex, Genetic Diversity, and Granulopoietic Cytokine Radiomitigation on Lifespan and Lymphoma Development in Murine H-ARS Survivors

Acute, high-dose radiation exposure results in life-threatening acute radiation syndrome (ARS) and debilitating delayed effects of acute radiation exposure (DEARE). The DEARE are a set of chronic multi-organ illnesses that can result in early death due to malignancy and other diseases. Animal models have proven essential in understanding the natural history of ARS and DEARE and licensure of medical countermeasures (MCM) according to the FDA Animal Rule. Our lab has developed models of hematopoietic (H)-ARS and DEARE in inbred C57BL/6J and Jackson Diversity Outbred (JDO) mice of both sexes and various ages and have used these models to identify mechanisms of radiation damage and effective MCMs. Herein, aggregate data from studies conducted over decades in our lab, consisting of 3,250 total-body lethally irradiated C57BL/6J young adult mice and 1,188 H-ARS survivors from these studies, along with smaller datasets in C57BL/6J pediatric and geriatric mice and JDO mice, were examined for lifespan and development of thymic lymphoma in survivors up to 3 years of age. Lifespan was found to be significantly shortened in H-ARS survivors compared to age-matched nonirradiated controls in all four models. Males and females exhibited similar lifespans except in the young adult C57BL/6J model where males survived longer than females after 16 months of age. The incidence of thymic lymphoma was increased in H-ARS survivors from the young adult and pediatric C57BL/6J models. Consistent with our findings in H-ARS, geriatric mice appeared more radioresistant than other models, with a lifespan and thymic lymphoma incidence more similar to nonirradiated controls than other models. Increased levels of multiple pro-inflammatory cytokines in DEARE bone marrow and serum correlated with shortened lifespan and malignancy, consistent with other animal models and human data. Of interest, G-CSF levels in bone marrow and serum 8-11 months after irradiation were significantly increased in females. Importantly, treatment with granulopoietic cytokine MCM for radiomitigation of H-ARS did not influence the long-term survival rate or incidence of thymic lymphoma in any model. Taken together, these findings indicate that the lifespan of H-ARS survivors was significantly decreased regardless of age at time of exposure or genetic diversity, and was unaffected by earlier treatment with granulopoietic cytokines for radiomitigation of H-ARS.

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.

Incidence risk of hepatobiliary malignant neoplasms in the cohort of workers chronically exposed to ionizing radiation

The increased risk of liver malignancies was found in workers of the first Russian nuclear production facility, Mayak Production Association, who had been chronically exposed to gamma rays externally and to alpha particles internally due to plutonium inhalation. In the present study, we updated the radiogenic risk estimates of the hepatobiliary malignancies using the extended follow-up period (1948-2018) of the Mayak worker cohort and the improved «Mayak worker dosimetry system-2013». The cohort comprised 22,377 workers hired at the Mayak PA between 1948 and 1982. The analysis considered 62 liver malignancies (32 hepatocellular carcinomas, 13 intrahepatic cholangiocarcinomas, 16 angiosarcomas, and 1 anaplastic cancer) and 33 gallbladder adenocarcinomas. The analysis proved the positive significant association of the liver malignancy risk (the total of histological types, hepatocellular carcinoma) with the liver absorbed alpha dose from internal exposure. The excess relative risk per Gy (95% confidence interval) of alpha dose (the linear model) was 7.56 (3.44; 17.63) for the total of histological types and 3.85 (0.95; 13.30) for hepatocellular carcinoma. Indications of non-linearity were observed in the dose-response for internal exposure to alpha radiation. No impact of external gamma-ray exposure on the liver malignancy incidence was found. In the study cohort, the number of angiosarcomas among various types of liver malignancies was very high (25.8%), and most of these tumors (73.3%) were registered in individuals internally exposed to alpha radiation at doses ranging between 6.0 and 21.0 Gy. No association with chronic occupational radiation exposure was observed for the incidence of gallbladder malignancies.

Recommendations on statistical approaches to account for dose uncertainties in radiation epidemiologic risk models

PURPOSE

Epidemiological studies of stochastic radiation health effects such as cancer, meant to estimate risks of the adverse effects as a function of radiation dose, depend largely on estimates of the radiation doses received by the exposed group under study. Those estimates are based on dosimetry that always has uncertainty, which often can be quite substantial. Studies that do not incorporate statistical methods to correct for dosimetric uncertainty may produce biased estimates of risk and incorrect confidence bounds on those estimates. This paper reviews commonly used statistical methods to correct radiation risk regressions for dosimetric uncertainty, with emphasis on some newer methods. We begin by describing the types of dose uncertainty that may occur, including those in which an uncertain value is shared by part or all of a cohort, and then demonstrate how these sources of uncertainty arise in radiation dosimetry. We briefly describe the effects of different types of dosimetric uncertainty on risk estimates, followed by a description of each method of adjusting for the uncertainty.

CONCLUSIONS

Each of the method has strengths and weaknesses, and some methods have limited applicability. We describe the types of uncertainty to which each method can be applied and its pros and cons. Finally, we provide summary recommendations and touch briefly on suggestions for further research.

Revisiting an Inverse Dose-Fractionation Effect of Ionizing Radiation Exposure for Ischemic Heart Disease: Insights from Recent Studies

Over the last two decades, there has been emerging evidence suggesting that ionizing radiation exposures could be associated with elevated risks of cardiovascular disease (CVD), particularly ischemic heart disease (IHD). Excess CVD risks have been observed in a number of exposed groups, with generally similar risk estimates both at low and high radiation doses and dose rates. In 2014, we reported for the first time significantly higher risks of IHD mortality when radiation doses were delivered over a protracted period of time (an inverse dose-fractionation effect) in the Canadian Fluoroscopy Cohort Study. Here we review the current evidence on the dose-fractionation effect of radiation exposure, discuss potential implication for radiation protection policies and suggest further directions for research in this area.

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.

The Impact of the Linear No-threshold Hypothesis on Litigation

ABSTRACT

As the basis of radiation safety practice and regulations worldwide, the linear no-threshold (LNT) hypothesis exerts enormous influence throughout society. This includes our judicial system, where frivolous lawsuits are filed alleging radiation-induced health effects caused by negligent companies who subject unwitting victims to enormous financial and physical harm. Typically, despite the lack of any supporting scientific basis, these cases result in enormous costs to organizations, insurance companies, and consumers.

Low Dose Radiation and Solid Tumors Mortality Risk

BACKGROUND

US nuclear capable shipyard workers have increased potential for occupational radiation exposure.

OBJECTIVE

The aim of the study is to examine solid tumor mortality risks at low doses.

METHOD

437,937 workers working from 1957 to 2004 at eight US shipyards were studied.

RESULTS

Radiation workers with a median life-time dose at 0.82 mSv had a significantly lower solid tumor mortality risk (relative risk [RR]: 0.96, 95% confidence interval [CI]: 0.94-0.98) than nonradiation workers. Among 153,930 radiation workers, the RRs of solid tumors increased with increasing dose categories without statistical significance. The dose category >0-<25 mSv had significantly lower RR (0.95, 95% CI: 0.91-0.99) versus 0 dose and the excess relative risk was 0.05/100 mSv (95% CI: 0.01-0.08).

CONCLUSIONS

Solid tumor risk might increase with radiation dose, but not linearly at low doses. Actual mortality risk may be dependent on dose received.

If You Torture Your Data Long Enough, It Will Confess to Anything: On the Epidemiological Basis of the LNT Model

This note deals with epidemiological data interpretation supporting the linear no-threshold model, as opposed to emerging evidence of adaptive response and hormesis from molecular biology in vitro and animal models. Particularly, the US-Japan Radiation Effects Research Foundation's lifespan study of atomic bomb survivors is scrutinized. We stress the years-long lag of the data processing after data gathering and evolving statistical models and methodologies across publications. The necessity of cautious interpretation of radiation epidemiology results is emphasized.

Low-dose CT: A safe and effective imaging modality in post-operative pelvic & acetabular fixation

INTRODUCTION

Post-operative pelvic & acetabular fixation patients are conventionally imaged using 3-view radiographs (AP, inlet and outlet). The efficacy of such radiographs is inconsistent due to technical difficulties capturing an adequate view, often necessitating repeat radiographs and therefore increasing radiation exposure. Radiographs can be difficult to interpret, limiting the assessment of fracture reduction and fixation, especially with respect to metalwork positioning around articular surfaces. Traditionally, post-operative pelvic & acetabular fixation patients undergo repeat 3-view radiographs post-operatively, at 6 weeks, followed by at 3, 6, 12, 18 and 24 months. We propose a new pathway, in which patients have one low-dose pelvic CT immediately post-operatively, followed by one radiograph (AP pelvis) at the same time points.

METHODS

A new pelvic CT protocol was created to provide high quality 3D imaging whilst delivering a 5 times lower radiation dose (compared to normal pelvic CT). Data for all pelvic radiographs and CTs between January 2021 and March 2022 was exported. Using dose area product values, effective radiation dose and attributable lifetime cancer risk were calculated.

RESULTS

There were 42 patients included in the analysis (age range 15 to 87).The average effective dose for the 3-view pelvic X-rays was 0.6mSv (range 0.2 to 2.8mSv), and 1.1mSv (range 0.5 to 2.2mSv) for the low-dose pelvic CT. Traditional 7 × 3-view post-operative radiographs: 7 × 0.6mSv = 4.2mSv (corresponding to 1 in 11,000 cancer risk) Low dose post-operative CT and 6 × 1-view radiographs: 1.1mSv + (6 × 0.6mSv / 3) = 2.3mSv (corresponding to 1 in 20,000 cancer risk) CONCLUSION: Low-dose CT scanning (in conjunction with 1-view radiographs) is an effective and safe imaging modality in the post-operative assessment of pelvic & acetabular fracture fixation, conferring a lower radiation burden, easier logistics, and higher quality images when compared to the traditional pathway of 3-view radiographs.

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.

Medical radiation exposure in inflammatory bowel disease: an updated meta-analysis

BACKGROUND

There have been previous studies and earlier systematic review on the relationship between inflammatory bowel disease (IBD) and radiation exposure. With the diversification of current test methods, this study intended to conduct a meta-analysis to evaluate the IBD radiation exposure in recent years.

METHODS

Three databases (PUBMED, EMBASE, and MEDICINE) for relevant literature up to May 1, 2023 were searched. The statistical data meeting requirements were collated and extracted.

RESULTS

20 papers were enrolled. The overall high radiation exposure rate was 15% (95% CI = [12%, 19%]) for CD and 5% (95% CI = [3%, 7%]) for UC. The pooled result found that high radiation exposure rate was 3.44 times higher in CD than in UC (OR = 3.44, 95% CI = [2.35, 5.02]). Moreover, the average radiation exposure level in CD was 12.77 mSv higher than that in UC (WMD = 12.77, 95% CI = [9.93, 15.62] mSv). Furthermore, radiation exposure level of CD after 2012 was higher than those before 2012 (26.42 ± 39.61vs. 23.76 ± 38.46 mSv, P = 0.016), while UC did not show similar result (11.99 ± 27.66 vs. 10.01 ± 30.76 mSv, P = 0.1). Through subgroup analysis, it was found that disease duration (WMD = 2.75, 95% CI = [0.10, 5.40] mSv), complications (OR = 5.09, 95% CI = [1.50, 17.29]), and surgical history (OR = 5.46, 95% CI = [1.51, 19.69]) significantly increased the proportion of high radiation exposure.

CONCLUSION

This study found that radiation exposure level of IBD patients was high, which revealed the radiation risk in the process of diagnosis and treatment of IBD patients. In the future, longer follow-up and prospective studies are needed to reveal the relationship between high radiation exposure and solid tumorigenesis.

Radiation hazards of the Ukraine nuclear power plants: how can international blood and marrow stem cell transplant societies help?

Any conflict in countries that process nuclear power plants raises concerns of the potential radiation injuries to the people in that region and beyond such as the current conflict in Ukraine. International healthcare organizations and societies should prepare for the potential scenarios of nuclear incidents. The Worldwide Network for Blood and Marrow Transplantation (WBMT) and its members, have recent experience preparing for this type of events such as the Fukushima incident in 2011. In this article, we discuss the risks of radiation exposure, current guidelines, and scientific evidence on hematopoietic support, including the role of hematopoietic stem cell transplant (HCT) for those exposed to nuclear radiation, and the role that the WBMT and other global BMT societies can play in triaging and managing people suffering from radiation injuries.

The Use of Joint Models in Analysis of Aggregate Endpoints in RERF Cohort Studies

In radiation risk estimation based on the Radiation Effects Research Foundation (RERF) cohort studies, one common analysis is Poisson regression on radiation dose and background and effect modifying variables of an aggregate endpoint such as all solid cancer incidence or all non-cancer mortality. As currently performed, these analyses require selection of a surrogate radiation organ dose, (e.g., colon dose), which could conceptually be problematic since the aggregate endpoint comprises events arising from a variety of organs. We use maximum likelihood theory to compare inference from the usual aggregate endpoint analysis to analyses based on joint analysis. These two approaches are also compared in a re-analysis of RERF Life Span Study all cancer mortality. We show that, except for a trivial difference, these two analytic approaches yield identical inference with respect to radiation dose response and background and effect modification when based on a single surrogate organ radiation dose. When repeating the analysis with organ-specific doses, an interesting issue of bias in intercept parameters arises when dose estimates are undefined for one sex when sex-specific outcomes are included in the aggregate endpoint, but a simple correction will avoid this issue. Lastly, while the joint analysis formulation allows use of organ-specific doses, the interpretation of such an analysis for inference regarding an aggregate endpoint can be problematic. To the extent that analysis of radiation risk for an aggregate endpoint is of interest, the joint-analysis formulation with a single surrogate dose is an appropriate analytic approach, whereas joint analysis with organ-specific doses may only be interpretable if endpoints are considered separately for estimating dose response. However, for neither approach is inference about dose response well defined.

Obesity is associated with biliary tract cancer mortality and incidence: A pooled analysis of 21 cohort studies in the Asia Cohort Consortium

Body fatness is considered a probable risk factor for biliary tract cancer (BTC), whereas cholelithiasis is an established factor. Nevertheless, although obesity is an established risk factor for cholelithiasis, previous studies of the association of body mass index (BMI) and BTC did not take the effect of cholelithiasis fully into account. To better understand the effect of BMI on BTC, we conducted a pooled analysis using population-based cohort studies in Asians. In total, 905 530 subjects from 21 cohort studies participating in the Asia Cohort Consortium were included. BMI was categorized into four groups: underweight (<18.5 kg/m2 ); normal (18.5-22.9 kg/m2 ); overweight (23-24.9 kg/m2 ); and obese (25+ kg/m2 ). The association between BMI and BTC incidence and mortality was assessed using hazard ratios (HR) and 95% confidence intervals (CIs) by Cox regression models with shared frailty. Mediation analysis was used to decompose the association into a direct and an indirect (mediated) effect. Compared to normal BMI, high BMI was associated with BTC mortality (HR 1.19 [CI 1.02-1.38] for males, HR 1.30 [1.14-1.49] for females). Cholelithiasis had significant interaction with BMI on BTC risk. BMI was associated with BTC risk directly and through cholelithiasis in females, whereas the association was unclear in males. When cholelithiasis was present, BMI was not associated with BTC death in either males or females. BMI was associated with BTC death among females without cholelithiasis. This study suggests BMI is associated with BTC mortality in Asians. Cholelithiasis appears to contribute to the association; and moreover, obesity appears to increase BTC risk without cholelithiasis.

Effect of bolus materials on dose deposition in deep tissues during electron beam radiotherapy

Several materials are utilized in the production of bolus, which is essential for superficial tumor radiotherapy. This research aimed to compare the variations in dose deposition in deep tissues during electron beam radiotherapy when employing different bolus materials. Specifically, the study developed general superficial tumor models (S-T models) and postoperative breast cancer models (P-B models). Each model comprised a bolus made of water, polylactic acid (PLA), polystyrene, silica-gel or glycerol. Geant4 was employed to simulate the transportation of electron beams within the studied models, enabling the acquisition of dose distributions along the central axis of the field. A comparison was conducted to assess the dose distributions in deep tissues. In regions where the percentage depth dose (PDD) decreases rapidly, the relative doses (RDs) in the S-T models with silica-gel bolus exhibited the highest values. Subsequently, RDs for PLA, glycerol and polystyrene boluses followed in descending order. Notably, the RDs for glycerol and polystyrene boluses were consistently below 1. Within the P-B models, RDs for all four bolus materials are consistently below 1. Among them, the smallest RDs are observed with the glycerol bolus, followed by silica-gel, PLA and polystyrene bolus in ascending order. As PDDs are ~1-3% or smaller, the differences in RDs diminish rapidly until are only around 10%. For the S-T and P-B models, polystyrene and glycerol are the most suitable bolus materials, respectively. The choice of appropriate bolus materials, tailored to the specific treatment scenario, holds significant importance in safeguarding deep tissues during radiotherapy.

Third mortality follow-up of the Mallinckrodt uranium processing workers, 1942-2019

INTRODUCTION

Mallinckrodt Chemical Works was a uranium processing facility during the Manhattan Project from 1942 to 1966. Thousands of workers were exposed to low-dose-rates of ionizing radiation from external and internal sources. This third follow-up of 2514 White male employees updates cancer and noncancer mortality potentially associated with radiation and silica dust.

MATERIALS AND METHODS

Individual, annualized organ doses were estimated from film badge records (n monitored = 2514), occupational chest x-rays (n = 2514), uranium urinalysis (n = 1868), radium intake through radon breath measurements (n = 487), and radon ambient measurements (n = 1356). Silica dust exposure from pitchblende processing was estimated (n = 1317). Vital status and cause of death determination through 2019 relied upon the National Death Index and Social Security Administration Epidemiological Vital Status Service. The analysis included standardized mortality ratios (SMRs), Cox proportional hazards, and Poisson regression models.

RESULTS

Vital status was confirmed for 99.4% of workers (84.0% deceased). For a dose weighting factor of 1 for intakes of uranium, radium, and radon decay products, the mean and median lung doses were 65.6 and 29.9 mGy, respectively. SMRs indicated a difference in health outcomes between salaried and hourly workers, and more brain cancer deaths than expected [SMR: 1.79; 95% confidence interval (CI): 1.14, 2.70]. No association was seen between radiation and lung cancer [hazard ratio (HR) at 100 mGy: 0.93; 95%CI: 0.78, 1.11]. The relationship between radiation and kidney cancer observed in the previous follow-up was maintained (HR at 100 mGy: 2.07; 95%CI: 1.12, 3.79). Cardiovascular disease (CVD) also increased significantly with heart dose (HR at 100 mGy: 1.11; 95%CI: 1.02, 1.21). Exposures to dust ≥23.6 mg/m3-year were associated with nonmalignant kidney disease (NMKD) (HR: 3.02; 95%CI: 1.12, 8.16) and kidney cancer combined with NMKD (HR: 2.46; 95%CI: 1.04, 5.81), though without evidence of a dose-response per 100 mg/m3-year.

CONCLUSIONS

This third follow-up of Mallinckrodt uranium processors reinforced the results of the previous studies. There was an excess of brain cancers compared with the US population, although no radiation dose-response was detected. The association between radiation and kidney cancer remained, though potentially due to few cases at higher doses. The association between levels of silica dust ≥23.6 mg/m3-year and NMKD also remained. No association was observed between radiation and lung cancer. A positive dose-response was observed between radiation and CVD; however, this association may be confounded by smoking, which was unmeasured. Future work will pool these data with other uranium processing worker cohorts within the Million Person Study.

Differential patterns of reproductive and lifestyle risk factors for breast cancer according to birth cohorts among women in China, Japan and Korea

BACKGROUND

The birth cohort effect has been suggested to influence the rate of breast cancer incidence and the trends of associated reproductive and lifestyle factors. We conducted a cohort study to determine whether a differential pattern of associations exists between certain factors and breast cancer risk based on birth cohorts.

METHODS

This was a cohort study using pooled data from 12 cohort studies. We analysed associations between reproductive (menarche age, menopause age, parity and age at first delivery) and lifestyle (smoking and alcohol consumption) factors and breast cancer risk. We obtained hazard ratios (HRs) with 95% confidence intervals (CIs) using the Cox proportional hazard regression analysis on the 1920s, 1930s, 1940s and 1950s birth cohorts.

RESULTS

Parity was found to lower the risk of breast cancer in the older but not in the younger birth cohort, whereas lifestyle factors showed associations with breast cancer risk only among the participants born in the 1950s. In the younger birth cohort group, the effect size was lower for parous women compared to the other cohort groups (HR [95% CI] 0.86 [0.66-1.13] compared to 0.60 [0.49-0.73], 0.46 [0.38-0.56] and 0.62 [0.51-0.77]). Meanwhile, a higher effect size was found for smoking (1.45 [1.14-1.84] compared to 1.25 [0.99-1.58], 1.06 [0.85-1.32] and 0.86 [0.69-1.08]) and alcohol consumption (1.22 [1.01-1.48] compared to 1.10 [0.90-1.33], 1.15 [0.96-1.38], and 1.07 [0.91-1.26]).

CONCLUSION

We observed different associations of parity, smoking and alcohol consumption with breast cancer risk across various birth cohorts.

Contribution of radioactive particles to the post-explosion exposure of atomic bomb survivors implied from their stable chromosome aberration rates

Even today when nearly 80 years have passed after the atomic bomb (A-bomb) was dropped, there are still debates about the exact doses received by the A-bomb survivors. While initial airborne kerma radiation (or energy spectrum of emitted radiation) can be measured with sufficient accuracy to assess the radiation dose to A-bomb survivors, it is not easy to accurately assess the neutron dose including appropriate weighting of neutron absorbed dose. Particularly, possible post-explosion exposure due to the radioactive particles generated through neutron activation have been almost neglected so far, mainly because of a large uncertainty associated to the behavior of those particles. However, it has been supposed that contribution of such non-initial radiation exposure from the neutron-induced radioactive particles could be significant, according to the findings that the stable chromosomal aberration rates which indicate average whole-body radiation doses were found to be more than 30% higher for those exposed indoors than for those outdoors even at the same initial dose estimated for the Life Span Study. In this Mini Review article, the authors explain that such apparently controversial observations can be reasonably explained by assuming a higher production rate of neutron-induced radioactive particles in the indoor environment near the hypocenter.

Assessing the impact of neutron relative biological effectiveness on all solid cancer mortality risks in the Japanese atomic bomb survivors

PURPOSE

Risk analyses, based on relative biological effectiveness (RBE) estimates for neutrons relative to gammas, were performed; and the change in the curvature of the risk to dose response with increasing neutron RBE was analyzed using all solid cancer mortality data from the Radiation Effect Research Foundation (RERF). Results were compared to those based on incidence data.

MATERIALS AND METHODS

This analysis is based on RERF mortality data with separate neutron and gamma doses for colon doses, from which organ averaged doses could be calculated. A model for risk ratio variation with RBE was developed.

RESULTS

The best estimate of the neutron RBE considering mortality data was 200 (95% confidence interval (CI): 50-1010) for colon dose using the weighted-dose approach and for organ averaged dose 110 (95% CI: 30-350). The ERR risk ratios for all solid cancers combined, for the best fitting neutron RBE estimate and the neutron RBE of 10 result in a ratio of 0.54 (95% CI: 0.17-0.85) for colon dose and 0.55 (95% CI: 0.18-0.87) for organ averaged dose. The risk to dose response curvature became significantly negative (concave down) with increasing RBE, at a neutron RBE of 170 using colon dose and at an RBE of 90 using organ averaged dose for males when fitting a linear-quadratic dose response. For females, the curvature decreased toward linearity with increasing neutron RBE and remained significantly positive until RBE of 80 and 40 using colon and organ averaged dose, respectively. For higher neutron RBEs, no significant conclusion could be drawn about the shape of the dose-response curve.

CONCLUSIONS

Application of neutron RBE values higher than 10 results in substantially reduced cancer mortality risk estimates and a significant reduction in curvature of the risk to dose responses for males. Using mortality data, the best fitting neutron RBE is much higher than when incidence data is used. The neutron RBE ranges covered by the overlap in the CIs from both the mortality and incidence analyses are 50-190 using colon dose and in all cases, the best fitting neutron RBE and lower 95% CI are higher than the value of 10 traditionally applied by the RERF. Therefore, it is recommended to consider uncertainties in neutron RBE values when calculating radiation risks and discussing the shape of dose responses using Japanese A-bomb survivors data.

Introduction to Nutrition and Cancer

By the beginning of the year 2021, the estimated number of new cancer cases worldwide was about 19.3 million and there were 10.0 million cancer-related deaths. Cancer is one of the deadliest diseases worldwide that can be attributed to genetic and environmental factors, including nutrition. The good nutrition concept focuses on the dietary requirements to sustain life. There is a substantial amount of evidence suggesting that a healthy diet can modulate cancer risk, particularly the risk of colorectal and breast cancers. Many studies have evaluated the correlation between our diet and the risk of cancer development, prevention, and treatment. The effect of diet on cancer development is likely to happen through intertwining mechanisms including inflammation and immune responses. For instance, a greater intake of red and processed meat along with low consumption of fruits and vegetables has been associated with increased levels of inflammatory biomarkers that are implicated in cancer development. On the other hand, the consumption of phytosterols, vitamins, and minerals, which exert antioxidant and anti-inflammatory roles have been linked to lower cancer risk, or even its occurrence prevention. In this book, we aim to summarize the current knowledge on the role of nutrition in cancer to provide the best scientific advice in this regard.

Active Breathing Coordinator reduces radiation dose to the stomach in patients with left breast cancer

BACKGROUND/PURPOSE

Gastric dose parameters comparison for deep inspiration breath-hold (DIBH) or free breathing (FB) mode during radiotherapy (RT) for left-sided breast cancer patients (LSBCPs) has not been investigated before. This study aimed to analyze the impact of Active Breath Coordinator (ABC)-DIBH technique on the dose received by the stomach during RT for LSBCPs and to provide organ-specific dosimetric parameters.

MATERIALS AND METHODS

The study included 73 LSBCPs. The dosimetric parameters of the stomach were compared between FB and DIBH mode. The correlation between the stomach volume and dosimetric parameters was analyzed.

RESULTS

Compared to FB mode, statistically significant reductions were observed in gastric dose parameters in ABC-DIBH mode, including Dmax (46.60 vs 17.25, p < 0.001), D1cc (38.42 vs 9.60, p < 0.001), Dmean (4.10 vs 0.80, p < 0.001), V40Gy (0.50 vs 0.00, p < 0.001), V30Gy (6.30 vs 0.00, p < 0.001), V20Gy (20.80 vs 0.00, p < 0.001), V10Gy (51.10 vs 0.77, p < 0.001), and V5Gy (93.20 vs 9.60, p < 0.001). ABC-DIBH increased the distance between the stomach and the breast PTV when compared to FB, from 1.3 cm to 2.8 cm (p < 0.001). Physiologic decrease in stomach volume was not found from FB to ABC-DIBH (415.54 cm3 vs 411.61 cm3, p = 0.260). The stomach volume showed a positive correlation with V40Gy (r2 = 0.289; p < 0.05), V30Gy (r2 = 0.287; p < 0.05), V20Gy (r2 = 0.343; p < 0.05), V10Gy (r2 = 0.039; p < 0.001), V5Gy (r2 = 0.439; p < 0.001), Dmax (r2 = 0.269; p < 0.05) and D1cc (r2 = 0.278; p < 0.05) in FB mode. While in ABC-DIBH mode, most stomach dosimetric parameters were not correlated with gastric volume.

CONCLUSIONS

The implementation of ABC-DIBH in LSBCPs radiotherapy resulted in lower irradiation of the stomach. Larger stomach volume was associated with statistically significantly higher dose irradiation in FB mode. To reduce radiotherapy related side effects in FB mode, patients should be fast for at least 2 hours before the CT simulation and treatment.

Modern universal standardised trends in worker and public exposure monitoring and control in 21st century by Sohrabi URPS-based hypothesis

The Universal Radiation Protection System (URPS) was recently hypothesised by Sohrabi in order to address the many deficiencies of current radiation protection system. The ICRP system is currently practiced worldwide based on the linear no-threshold (LNT) model with no supporting health risk data at low effective doses. The ICRP only considers worker occupational doses and sets dose limits only on one portion of doses a worker or public receives. The URPS hypothesis equals human heath-effect risks per unit dose either from natural or man-made sources; formulates dose limits on all integrated doses an individual receives; considers worker also a member of public; conserves 'cause-effect principle' for epidemiology risk estimation; introduces dose fractionation concept in radiation protection; introduces the 'URPS Model' for bridging LNT, hormesis and threshold models; recommends establishing 'National Patient Dose Registering System'; and defines modified/new exposure terms and definitions commensurate with URPS hypothesis, as advanced since 2014.

Newly discovered genomic mutation patterns in radiation-induced small intestinal tumors of ApcMin/+ mice

Among the small intestinal tumors that occur in irradiated mice of the established mouse model B6/B6-Chr18MSM-F1 ApcMin/+, loss of heterozygosity analysis can be utilized to estimate whether a deletion in the wild-type allele containing the Adenomatous polyposis coli (Apc) region (hereafter referred to as Deletion), a duplication in the mutant allele with a nonsense mutation at codon 850 of Apc (Duplication), or no aberration (Unidentified) has occurred. Previous research has revealed that the number of Unidentified tumors tends to increase with the radiation dose. In the present study, we investigated the molecular mechanisms underlying the development of an Unidentified tumor type in response to radiation exposure. The mRNA expression levels of Apc were significantly lower in Unidentified tumors than in normal tissues. We focused on epigenetic suppression as the mechanism underlying this decreased expression; however, hypermethylation of the Apc promoter region was not observed. To investigate whether deletions occur that cannot be captured by loss of heterozygosity analysis, we analyzed chromosome 18 using a customized array comparative genomic hybridization approach designed to detect copy-number changes in chromosome 18. However, the copy number of the Apc region was not altered in Unidentified tumors. Finally, gene mutation analysis of the Apc region using next-generation sequencing suggested the existence of a small deletion (approximately 3.5 kbp) in an Unidentified tumor from a mouse in the irradiated group. Furthermore, nonsense and frameshift mutations in Apc were found in approximately 30% of the Unidentified tumors analyzed. These results suggest that radiation-induced Unidentified tumors arise mainly due to decreased Apc expression of an unknown regulatory mechanism that does not depend on promoter hypermethylation, and that some tumors may result from nonsense mutations which are as-yet undefined point mutations.