Comparison of external dose estimates using different retrospective dosimetry methods in the settlements located near Semipalatinsk Nuclear Test Site, Republic of Kazakhstan

For correct assessment of health risks after low-dose irradiation, calculation of radiation exposure estimates is crucial. To verify the calculated absorbed doses, instrumental methods of retrospective dosimetry are used. We compared calculated and instrumental-based estimates of external absorbed doses in the residents of Dolon, Mostik and Cheremushki villages, Kazakhstan, affected by the first nuclear weapon test performed at the Semipalatinsk Nuclear Test Site (SNTS) on August 29, 1949. The 'instrumental' doses were retrospectively estimated using the Luminescence Retrospective Dosimetry (LRD) and Electron Spin Resonance (ESR) methods. Correlation between the calculated individual cumulative external absorbed whole-body doses based on typical input data and ESR-based individual doses in the same people was strong (r = 0.782). It was even stronger between the calculated doses based on individual questionnaires' input data and the ESR-based doses (r = 0.940). Application of the LRD method is useful for validation of the calculated settlement-average cumulated external absorbed dose to air. Reconstruction of external exposure can be supplemented with the data from later measurements of soil contamination with long-lived radionuclides, such as, 137Cs. Our results show the reliability of the calculational method used for the retrospective assessment of individual external doses.

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.

Cancer mortality after low dose exposure to ionising radiation in workers in France, the United Kingdom, and the United States (INWORKS): cohort study

OBJECTIVE

To evaluate the effect of protracted low dose, low dose rate exposure to ionising radiation on the risk of cancer.

DESIGN

Multinational cohort study.

SETTING

Cohorts of workers in the nuclear industry in France, the UK, and the US included in a major update to the International Nuclear Workers Study (INWORKS).

PARTICIPANTS

309 932 workers with individual monitoring data for external exposure to ionising radiation and a total follow-up of 10.7 million person years.

MAIN OUTCOME MEASURES

Estimates of excess relative rate per gray (Gy) of radiation dose for mortality from cancer.

RESULTS

The study included 103 553 deaths, of which 28 089 were due to solid cancers. The estimated rate of mortality due to solid cancer increased with cumulative dose by 52% (90% confidence interval 27% to 77%) per Gy, lagged by 10 years. Restricting the analysis to the low cumulative dose range (0-100 mGy) approximately doubled the estimate of association (and increased the width of its confidence interval), as did restricting the analysis to workers hired in the more recent years of operations when estimates of occupational external penetrating radiation dose were recorded more accurately. Exclusion of deaths from lung cancer and pleural cancer had a modest effect on the estimated magnitude of association, providing indirect evidence that the association was not substantially confounded by smoking or occupational exposure to asbestos.

CONCLUSIONS

This major update to INWORKS provides a direct estimate of the association between protracted low dose exposure to ionising radiation and solid cancer mortality based on some of the world's most informative cohorts of radiation workers. The summary estimate of excess relative rate solid cancer mortality per Gy is larger than estimates currently informing radiation protection, and some evidence suggests a steeper slope for the dose-response association in the low dose range than over the full dose range. These results can help to strengthen radiation protection, especially for low dose exposures that are of primary interest in contemporary medical, occupational, and environmental settings.

Investigation of Shared Genetic Risk Factors Between Parkinson's Disease and Cancers

BACKGROUND

Epidemiological studies that examined the association between Parkinson's disease (PD) and cancers led to inconsistent results, but they face a number of methodological difficulties.

OBJECTIVE

We used results from genome-wide association studies (GWASs) to study the genetic correlation between PD and different cancers to identify common genetic risk factors.

METHODS

We used individual data for participants of European ancestry from the Courage-PD (Comprehensive Unbiased Risk Factor Assessment for Genetics and Environment in Parkinson's Disease; PD, N = 16,519) and EPITHYR (differentiated thyroid cancer, N = 3527) consortia and summary statistics of GWASs from iPDGC (International Parkinson Disease Genomics Consortium; PD, N = 482,730), Melanoma Meta-Analysis Consortium (MMAC), Breast Cancer Association Consortium (breast cancer), the Prostate Cancer Association Group to Investigate Cancer Associated Alterations in the Genome (prostate cancer), International Lung Cancer Consortium (lung cancer), and Ovarian Cancer Association Consortium (ovarian cancer) (N comprised between 36,017 and 228,951 for cancer GWASs). We estimated the genetic correlation between PD and cancers using linkage disequilibrium score regression. We studied the association between PD and polymorphisms associated with cancers, and vice versa, using cross-phenotypes polygenic risk score (PRS) analyses.

RESULTS

We confirmed a previously reported positive genetic correlation of PD with melanoma (Gcorr = 0.16 [0.04; 0.28]) and reported an additional significant positive correlation of PD with prostate cancer (Gcorr = 0.11 [0.03; 0.19]). There was a significant inverse association between the PRS for ovarian cancer and PD (odds ratio [OR] = 0.89 [0.84; 0.94]). Conversely, the PRS of PD was positively associated with breast cancer (OR = 1.08 [1.06; 1.10]) and inversely associated with ovarian cancer (OR = 0.95 [0.91; 0.99]). The association between PD and ovarian cancer was mostly driven by rs183211 located in an intron of the NSF gene (17q21.31).

CONCLUSIONS

We show evidence in favor of a contribution of pleiotropic genes to the association between PD and specific cancers. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Response to Toshihide Tsuda, Yumiko Miyano and Eiji Yamamoto [1]

BACKGROUND

Using a toolkit approach, Tsuda et al. critiqued work carried out by or in collaboration with the International Agency for Research on Cancer (IARC/WHO), including the IARC technical publication No. 46 on "Thyroid health monitoring after nuclear accidents" (TM-NUC), the project on nuclear emergency situations and improvement on medical and health surveillance (SHAMISEN), and the IARC-led work on global thyroid cancer incidence patterns as per IARC core mandate.

MAIN BODY

We respond on the criticism of the recommendations of the IARC technical publication No. 46, and of global thyroid cancer incidence evaluation.

CONCLUSION

After nuclear accidents, overdiagnosis can still happen and must be included in informed decision making when providing a system of optimal help for cases of radiation-induced thyroid cancer, to minimize harm to people by helping them avoid diagnostics and treatment they may not need.

Brain cancer after radiation exposure from CT examinations of children and young adults: results from the EPI-CT cohort study

BACKGROUND

The European EPI-CT study aims to quantify cancer risks from CT examinations of children and young adults. Here, we assess the risk of brain cancer.

METHODS

We pooled data from nine European countries for this cohort study. Eligible participants had at least one CT examination before age 22 years documented between 1977 and 2014, had no previous diagnosis of cancer or benign brain tumour, and were alive and cancer-free at least 5 years after the first CT. Participants were identified through the Radiology Information System in 276 hospitals. Participants were linked with national or regional registries of cancer and vital status, and eligible cases were patients with brain cancers according to WHO International Classification of Diseases for Oncology. Gliomas were analysed separately to all brain cancers. Organ doses were reconstructed using historical machine settings and a large sample of CT images. Excess relative risks (ERRs) of brain cancer per 100 mGy of cumulative brain dose were calculated with linear dose-response modelling. The outcome was the first reported diagnosis of brain cancer after an exclusion period of 5 years after the first electronically recorded CT examination.

FINDINGS

We identified 948 174 individuals, of whom 658 752 (69%) were eligible for our study. 368 721 (56%) of 658 752 participants were male and 290 031 (44%) were female. During a median follow-up of 5·6 years (IQR 2·4-10·1), 165 brain cancers occurred, including 121 (73%) gliomas. Mean cumulative brain dose, lagged by 5 years, was 47·4 mGy (SD 60·9) among all individuals and 76·0 mGy (100·1) among people with brain cancer. A significant linear dose-response relationship was observed for all brain cancers (ERR per 100 mGy 1·27 [95% CI 0·51-2·69]) and for gliomas separately (ERR per 100 mGy 1·11 [0·36-2·59]). Results were robust when the start of follow-up was delayed beyond 5 years and when participants with possibly previously unreported cancers were excluded.

INTERPRETATION

The observed significant dose-response relationship between CT-related radiation exposure and brain cancer in this large, multicentre study with individual dose evaluation emphasises careful justification of paediatric CTs and use of doses as low as reasonably possible.

FUNDING

EU FP7; Belgian Cancer Registry; La Ligue contre le Cancer, L'Institut National du Cancer, France; Ministry of Health, Labour and Welfare of Japan; German Federal Ministry of Education and Research; Worldwide Cancer Research; Dutch Cancer Society; Research Council of Norway; Consejo de Seguridad Nuclear, Generalitat de Catalunya, Spain; US National Cancer Institute; UK National Institute for Health Research; Public Health England.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Dose Estimation for the European Epidemiological Study on Pediatric Computed Tomography (EPI-CT)

Within the European Epidemiological Study to Quantify Risks for Paediatric Computerized Tomography (EPI-CT study), a cohort was assembled comprising nearly one million children, adolescents and young adults who received over 1.4 million computed tomography (CT) examinations before 22 years of age in nine European countries from the late 1970s to 2014. Here we describe the methods used for, and the results of, organ dose estimations from CT scanning for the EPI-CT cohort members. Data on CT machine settings were obtained from national surveys, questionnaire data, and the Digital Imaging and Communications in Medicine (DICOM) headers of 437,249 individual CT scans. Exposure characteristics were reconstructed for patients within specific age groups who received scans of the same body region, based on categories of machines with common technology used over the time period in each of the 276 participating hospitals. A carefully designed method for assessing uncertainty combined with the National Cancer Institute Dosimetry System for CT (NCICT, a CT organ dose calculator), was employed to estimate absorbed dose to individual organs for each CT scan received. The two-dimensional Monte Carlo sampling method, which maintains a separation of shared and unshared error, allowed us to characterize uncertainty both on individual doses as well as for the entire cohort dose distribution. Provided here are summaries of estimated doses from CT imaging per scan and per examination, as well as the overall distribution of estimated doses in the cohort. Doses are provided for five selected tissues (active bone marrow, brain, eye lens, thyroid and female breasts), by body region (i.e., head, chest, abdomen/pelvis), patient age, and time period (1977-1990, 1991-2000, 2001-2014). Relatively high doses were received by the brain from head CTs in the early 1990s, with individual mean doses (mean of 200 simulated values) of up to 66 mGy per scan. Optimization strategies implemented since the late 1990s have resulted in an overall decrease in doses over time, especially at young ages. In chest CTs, active bone marrow doses dropped from over 15 mGy prior to 1991 to approximately 5 mGy per scan after 2001. Our findings illustrate patterns of age-specific doses and their temporal changes, and provide suitable dose estimates for radiation-induced risk estimation in epidemiological studies.

Multiethnic genome-wide association study of differentiated thyroid cancer in the EPITHYR consortium

Incidence of differentiated thyroid carcinoma (DTC) varies considerably between ethnic groups, with particularly high incidence rates in Pacific Islanders. DTC is one of the cancers with the highest familial risk suggesting a major role of genetic risk factors, but only few susceptibility loci were identified so far. In order to assess the contribution of known DTC susceptibility loci and to identify new ones, we conducted a multiethnic genome-wide association study (GWAS) in individuals of European ancestry and of Oceanian ancestry from Pacific Islands. Our study included 1554 cases/1973 controls of European ancestry and 301 cases/348 controls of Oceanian ancestry from seven population-based case-control studies participating to the EPITHYR consortium. All participants were genotyped using the OncoArray-500K Beadchip (Illumina). We confirmed the association with the known DTC susceptibility loci at 2q35, 8p12, 9q22.33 and 14q13.3 in the European ancestry population and suggested two novel signals at 1p31.3 and 16q23.2, which were associated with thyroid-stimulating hormone levels in previous GWAS. We additionally replicated an association with 5p15.33 reported previously in Chinese and European populations. Except at 1p31.3, all associations were in the same direction in the population of Oceanian ancestry. We also observed that the frequencies of risk alleles at 2q35, 5p15.33 and 16q23.2 were significantly higher in Oceanians than in Europeans. However, additional GWAS and epidemiological studies in Oceanian populations are needed to fully understand the highest incidence observed in these populations.

Gene network and biological pathways associated with susceptibility to differentiated thyroid carcinoma

Variants identified in earlier genome-wide association studies (GWAS) on differentiated thyroid carcinoma (DTC) explain about 10% of the overall estimated genetic contribution and could not provide complete insights into biological mechanisms involved in DTC susceptibility. Integrating systems biology information from model organisms, genome-wide expression data from tumor and matched normal tissue and GWAS data could help identifying DTC-associated genes, and pathways or functional networks in which they are involved. We performed data mining of GWAS data of the EPITHYR consortium (1551 cases and 1957 controls) using various pathways and protein-protein interaction (PPI) annotation databases and gene expression data from The Cancer Genome Atlas. We identified eight DTC-associated genes at known loci 2q35 (DIRC3), 8p12 (NRG1), 9q22 (FOXE1, TRMO, HEMGN, ANP32B, NANS) and 14q13 (MBIP). Using the EW_dmGWAS approach we found that gene networks related to glycogenolysis, glycogen metabolism, insulin metabolism and signal transduction pathways associated with muscle contraction were overrepresented with association signals (false discovery rate adjusted p-value < 0.05). Additionally, suggestive association of 21 KEGG and 75 REACTOME pathways with DTC indicate a link between DTC susceptibility and functions related to metabolism of cholesterol, amino sugar and nucleotide sugar metabolism, steroid biosynthesis, and downregulation of ERBB2 signaling pathways. Together, our results provide novel insights into biological mechanisms contributing to DTC risk.

Breast cancer incidence in the regions of Belarus and Ukraine most contaminated by the Chernobyl accident: 1978 to 2016

Even 30 years after the accident, an association between breast cancer incidence and ionizing radiation exposure from Chernobyl fallout remains uncertain. We studied breast cancer incidence in the most contaminated regions of Belarus (Gomel and Mogilev) and Ukraine (Kyiv, Zhytomyr and Chernihiv) before (1978-1986) and after (1987-2016) the accident. Breast cancer cases and female population size data were received from the national cancer registries and the state departments of statistics. The study included 85 132 breast cancers with 150 million person-years at risk. We estimated annual rayon (district)-average absorbed doses to the breast from external and internal irradiation of the adult female population over the period of 1986-2016. We studied an association between rayon-average cumulative absorbed breast dose with 5-year lag, that is, excluding the exposure in 5 years prior to breast cancer diagnosis, and breast cancer incidence using negative binomial regression models. Mean (median) cumulative breast dose in 2016 was 12.3 (5.0) milligray (mGy) in Belarus and 5.7 (2.3) mGy in Ukraine, with the maximum dose of 55 mGy and 54 mGy, respectively. Breast cancer incidence rates statistically significantly increased with calendar year and attained age, and were higher in urban than in rural residents. Adjusting for time, age and urbanicity effects, we found no evidence of increasing incidence with rayon-average 5-year lagged cumulative breast dose. Owing to ecological study design limitations, a case-control study covering this area with individually reconstructed absorbed breast doses is needed testing for association between low-dose protracted radiation exposure and breast cancer risk after Chernobyl.

Fine-mapping of two differentiated thyroid carcinoma susceptibility loci at 2q35 and 8p12 in Europeans, Melanesians and Polynesians

Differentiated thyroid carcinoma (DTC) incidence is characterized by wide ethnic and geographic variations, with high incidence rates observed in Oceanian populations. Genome-wide association studies (GWAS) identified mainly four DTC susceptibility loci at 9q22.33, 14q13.3, 2q35 and 8p12. Here we performed fine-mapping of the 2q35 and 8p12 loci in the population of the EPITHYR consortium that includes Europeans, Melanesians and Polynesians to identify likely causal variants for DTC risk. We conducted a colocalization analysis using eQTLs data to determine the SNPs with the highest probability of causality. At 2q35, we highlighted rs16857609 located in DIRC3. This SNP has a high probability of causality in the three populations, and a significant association in Europeans (OR = 1.4, p = 1.9 x 10-10). It is also associated with expression of DIRC3 and of the nearby gene IGFBP5 in thyroid tumour cells. At 8p12, we identified rs7844425 which was significantly associated with DTC in Europeans (OR = 1.32, p = 7.6 x 10-8) and rs2439304, which was highlighted by the colocalization analysis but only moderately associated with DTC in our dataset (OR = 1.2, p = 0.001). These SNPs are linked to the expression of NRG1 in thyroid tissue. Hence, our study identified novel variants at 2q35 and 8p12 to be prioritized for further functional studies.

Risk of cancer associated with low-dose radiation exposure: comparison of results between the INWORKS nuclear workers study and the A-bomb survivors study

The Life Span Study (LSS) of Japanese atomic bomb survivors has served as the primary basis for estimates of radiation-related disease risks that inform radiation protection standards. The long-term follow-up of radiation-monitored nuclear workers provides estimates of radiation-cancer associations that complement findings from the LSS. Here, a comparison of radiation-cancer mortality risk estimates derived from the LSS and INWORKS, a large international nuclear worker study, is presented. Restrictions were made, so that the two study populations were similar with respect to ages and periods of exposure, leading to selection of 45,625 A-bomb survivors and 259,350 nuclear workers. For solid cancer, excess relative rates (ERR) per gray (Gy) were 0.28 (90% CI 0.18; 0.38) in the LSS, and 0.29 (90% CI 0.07; 0.53) in INWORKS. A joint analysis of the data allowed for a formal assessment of heterogeneity of the ERR per Gy across the two studies (P = 0.909), with minimal evidence of curvature or of a modifying effect of attained age, age at exposure, or sex in either study. There was evidence in both cohorts of modification of the excess absolute risk (EAR) of solid cancer by attained age, with a trend of increasing EAR per Gy with attained age. For leukemia, under a simple linear model, the ERR per Gy was 2.75 (90% CI 1.73; 4.21) in the LSS and 3.15 (90% CI 1.12; 5.72) in INWORKS, with evidence of curvature in the association across the range of dose observed in the LSS but not in INWORKS; the EAR per Gy was 3.54 (90% CI 2.30; 5.05) in the LSS and 2.03 (90% CI 0.36; 4.07) in INWORKS. These findings from different study populations may help understanding of radiation risks, with INWORKS contributing information derived from cohorts of workers with protracted low dose-rate exposures.

Living conditions and health status of populations living in territories impacted by nuclear accidents - Some lessons for developing health surveillance programme

This paper explores how health concerns of populations living in contaminated areas following radiological accidents can be considered in developing health surveillance. The research was performed in the framework of the SHAMISEN project, and aimed at identifying the impacts on, and challenges associated with, living and social conditions of affected populations. These objectives were achieved through the analysis of specific Case Studies in different situations observed after the Chernobyl accident (Belarus and Norway) and the activities carried out after the Fukushima accident. It incorporates an analysis of testimonies of medical experts and local stakeholders from contaminated territories in Japan within two Case Studies as well as through a dedicated workshop jointly organised with Fukushima Medical University in Japan in March 2016. The analysis addresses the following topics:Thus, this paper outlines key lessons learned from each of these topics, by providing tangibles examples from the analysis of the various Case Studies.

The SHAMISEN Project: Challenging historical recommendations for preparedness, response and surveillance of health and well-being in case of nuclear accidents: Lessons learnt from Chernobyl and Fukushima

Experience suggests that current nuclear accident response planning in European countries mostly has a technical focus, with less attention paid to social, psychological and ethical issues. Information provided tends to be directed towards decisions made by experts, rather than for the support of affected populations. The SHAMISEN (Nuclear Emergency Situations - Improvement of Medical And Health Surveillance) consortium, composed of close to 50 experts from 10 countries, performed a critical review of current recommendations and experiences regarding dose assessment and reconstruction, evacuation decisions, long-term health surveillance programmes and epidemiological studies. The review included case studies and lessons drawn from the living conditions and health status of populations affected by the Chernobyl and Fukushima accidents, taking an integrative approach to health and well-being. Based on this work, SHAMISEN developed a series of comprehensive recommendations aimed at improving the preparedness, response, long-term surveillance and living conditions of populations affected by past or future radiation accidents, in a manner responding to their needs, while minimising unnecessary anxiety.

Lessons learned from Chernobyl and Fukushima on thyroid cancer screening and recommendations in case of a future nuclear accident

Exposure of the thyroid gland to ionizing radiation at a young age is the main recognized risk factor for differentiated thyroid cancer. After the Chernobyl and Fukushima nuclear accidents, thyroid cancer screening was implemented mainly for children, leading to case over-diagnosis as seen in South Korea after the implementation of opportunistic screening (where subjects are recruited at healthcare sites). The aim of cancer screening is to reduce morbidity and mortality, but screening can also cause negative effects on health (with unnecessary treatment if over-diagnosis) and on quality of life. This paper from the SHAMISEN special issue (Nuclear Emergency Situations - Improvement of Medical And Health Surveillance) presents the principles of cancer screening, the lessons learned from thyroid cancer screening, as well as the knowledge on thyroid cancer incidence after exposure to iodine-131. The SHAMISEN Consortium recommends to envisage systematic health screening after a nuclear accident, only when appropriately justified, i.e. ensuring that screening will do more good than harm. Based on the experience of the Fukushima screening, the consortium does not recommend mass or population-based thyroid cancer screening, as the negative psychological and physical effects are likely to outweigh any possible benefit in affected populations; thyroid health monitoring should however be made available to persons who request it (regardless of whether they are at increased risk or not), accompanied with appropriate information and support.

Computed tomography of the head and the risk of brain tumours during childhood and adolescence: results from a case-control study in Japan

To clarify whether medical radiation exposure, especially from head computed tomography (CT), increases the risk of brain tumours in young patients in Japan, which ranks the second highest in the world in the number of paediatric CT examinations following the US. From 2011 to 2015, we performed a case-control study of 120 brain tumour patients and 360 appendicitis patients as controls. Reasons, the number of brain and head CT scans date were available from interviews. A cumulative radiation dose to the brain was calculated as a sum of doses received from head CT scans and from conventional X-rays and estimated using a reference table derived from a literature review of published studies. We performed conditional logistic regression to assess the risk of brain tumours from brain and head CT, and from conventional head X-ray procedures. The case group received on average 1.8 CTs to the brain area and 2.2 CTs to the whole head, with a mean estimated brain dose of 32 ±13 mGy. The odds ratio for developing a brain tumour from having a brain CT was 0.93 (95% confidence interval: 0.38-1.82). This was hardly altered when adjusting for parental educational history and for other diseases (history of neurological disease and attention-deficit disorder/attention-deficit hyperactivity disorder). Neither whole head CT nor cumulative brain dose to the brain increased the risk of glioma or of all brain tumours. Although this study conducted in Japan, where ranks second in the number of CT scans conducted in the world, did not show an increased risk of brain tumours related to CT scans, it should be taken with caution due to a case-control study with limited sample size.

Uncertainties in Radiation Doses for a Case-control Study of Thyroid Cancer among Persons Exposed in Childhood to 131 I from Chernobyl Fallout

Uncertainties in thyroid doses due to I intake were evaluated for 2,239 subjects in a case-control study of thyroid cancer following exposure to Chernobyl fallout during childhood and adolescence carried out in contaminated regions of Belarus and Russia. Using new methodological developments that became available recently, a Monte Carlo simulation procedure was applied to calculate 1,000 alternative vectors of thyroid doses due to I intake for the study population of 2,239 subjects accounting for sources of shared and unshared errors. An overall arithmetic mean of the stochastic thyroid doses in the study was estimated to be 0.43 Gy and median dose of 0.16 Gy. The arithmetic mean and median of deterministic doses estimated previously for 1,615 of 2,239 study subjects were 0.48 Gy and 0.20 Gy, respectively. The geometric standard deviation of individual stochastic doses varied from 1.59 to 3.61 with an arithmetic mean of 1.94 and a geometric mean of 1.89 over all subjects of the study. These multiple sets of thyroid doses were used to update radiation-related thyroid cancer risks in the study population exposed to I after the Chernobyl accident.

Thyroid Cancer after Exposure to Radioiodine in Childhood and Adolescence: 131I-Related Risk and the Role of Selected Host and Environmental Factors

In this study, we expanded on a previously published population-based case-control study on subjects exposed to iodine-131 (131I) from Chernobyl fallout at age ≤18 years using improved individual 131I absorbed thyroid doses. We further studied the impact of iodine deficiency and other selected host risk factors on 131I-related thyroid cancer risk after childhood exposure. We included 298 thyroid cancer cases and 1934 matched controls from the most contaminated regions of Belarus and the Russian Federation. We performed statistical analysis using conditional logistic regression models. We found a statistically significant linear quadratic dose-effect association between thyroid cancer and 131I thyroid dose in the range up to 5 grays (Gy). Self-reported personal history of benign nodules, any thyroid disease except thyroid cancer, family history of thyroid cancer, increased body mass index, and deficient stable iodine status at the time of the accident were statistically significant risk factors (p < 0.05 for each factor) for thyroid cancer after adjustment for thyroid 131I dose effect. Subjects who received stable iodine supplementation in the years after the accident had a significantly lower 131I-related risk of thyroid cancer. Our findings are important for thyroid cancer prevention, and for further improvement of medical surveillance in the affected populations.

The risk of cancer attributable to diagnostic medical radiation: Estimation for France in 2015

Although medical ionizing radiation (IR) has clear clinical benefits, it is an established carcinogen. Our study estimates the number of new cancer cases in France in 2015 attributable to IR exposure from medical procedures. Exposures from external (X-rays, CT scans, interventional radiology) and internal (nuclear medicine) sources were considered. We used 2007 national frequencies of diagnostic examinations by sex and age to estimate the lifetime organ dose exposure adjusted for changes in the use of such procedures over time. The Biological Effects of Ionizing Radiation VII risk models were used to estimate the corresponding excess cancer risk, assuming an average latency period of 10 years. Additionally, we used cancer incidence data from the French Cancer Registries Network. Of the 346,000 estimated new cancer cases in adults in France in 2015, 2300 cases (940 among men and 1360 among women) were attributable to diagnostic IR, representing 0.7% of all new cancer cases (0.5% for men and 0.9% for women). The leading cancers attributable to medical IR were female breast (n = 560 cases), lung (n = 500 cases) and colon (n = 290 cases) cancers. Compared to other risk factors, the contribution of medical IR to the cancer burden is small, and the benefits largely outweigh its harms. However, some of these IR-associated cancer cases may be preventable through dose optimization of and enhanced justification for diagnostic examinations.

Exposure to loud noise and risk of vestibular schwannoma: results from the INTERPHONE international case‒control study

Objective Studies of loud noise exposure and vestibular schwannomas (VS) have shown conflicting results. The population-based INTERPHONE case‒control study was conducted in 13 countries during 2000-2004. In this paper, we report the results of analyses on the association between VS and self-reported loud noise exposure. Methods Self-reported noise exposure was analyzed in 1024 VS cases and 1984 matched controls. Life-long noise exposure was estimated through detailed questions. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using adjusted conditional logistic regression for matched sets. Results The OR for total work and leisure noise exposure was 1.6 (95% CI 1.4-1.9). OR were 1.5 (95% CI 1.3-1.9) for only occupational noise, 1.9 (95% CI 1.4-2.6) for only leisure noise and 1.7 (95% CI 1.2-2.2) for exposure in both contexts. OR increased slightly with increasing lag-time. For occupational exposures, duration, time since exposure start and a metric combining lifetime duration and weekly exposure showed significant trends of increasing risk with increasing exposure. OR did not differ markedly by source or other characteristics of noise. Conclusion The consistent associations seen are likely to reflect either recall bias or a causal association, or potentially indicate a mixture of both.

The State Scientific Automated Medical Registry, Kazakhstan: an important resource for low-dose radiation health research

Direct quantitative assessment of health risks following exposure to ionizing radiation is based on findings from epidemiological studies. Populations affected by nuclear bomb testing are among those that allow such assessment. The population living around the former Soviet Union's Semipalatinsk nuclear test site is one of the largest human cohorts exposed to radiation from nuclear weapons tests. Following research that started in the 1960s, a registry that contains information on more than 300,000 individuals residing in the areas neighboring to the test site was established. Four nuclear weapons tests, conducted from 1949 to 1956, resulted in non-negligible radiation exposures to the public, corresponding up to approximately 300 mGy external dose. The registry contains relevant information about those who lived at the time of the testing as well as about their offspring, including biological material. An international group of scientists worked together within the research project SEMI-NUC funded by the European Union, and concluded that the registry provides a novel, mostly unexplored, and valuable resource for the assessment of the population risks associated with environmental radiation exposure. Suggestions for future studies and pathways on how to use the best dose assessment strategies have also been described in the project. Moreover, the registry could be used for research on other relevant public health topics.

Automated scoring of dicentric chromosomes differentiates increased radiation sensitivity of young children after low dose CT exposure in vitro

PURPOSE

Automated detection of dicentric chromosomes from a large number of cells was applied to study age-dependent radiosensitivity after in vitro CT exposure of blood from healthy donors.

MATERIALS AND METHODS

Blood samples from newborns, children (2-5 years) and adults (20-50 years) were exposed in vitro to 0 mGy, 41 mGy and 978 mGy using a CT equipment. In this study, automated scoring based on 13,000-31,000 cells/dose point/age group was performed. Results for control and low dose points were validated by manually counting about 26,000 cells/dose point/age group.

RESULTS

For all age groups, the high number of analyzed cells enabled the detection of a significant increase in the frequency of radiation induced dicentric chromosomes in cells exposed to 41 mGy as compared to control cells. Moreover, differences between the age groups could be resolved for the low dose: young donors showed significantly increased risk for induced dicentrics at 41 mGy compared to adults.

CONCLUSIONS

The results very clearly demonstrate that the automated dicentric scoring method is capable of discerning radiation induced biomarkers in the low dose range (<100 mGy) and thus may open possibilities for large-scale molecular epidemiology studies in radiation protection.

Cancer risk from paediatric computed tomography scanning: implications for radiation protection in medicine

The use of computed tomography (CT) imaging is clearly beneficial for millions of patients. However, the potential adverse health effects, particularly cancer, of ionising radiation exposure from CT early in life are an issue of growing concern in the radiological protection, medical, and public health communities. Although efforts to quantify these effects have been conducted, the precision and accuracy of reported risks needs confirmation. EPI-CT, a European collaborative epidemiological study, was set up to quantify risks from paediatric CT to optimise paediatric diagnostic protocol. The study, coordinated by the International Agency for Research on Cancer, was designed as a multi-national cohort study of children and young adults who underwent CT scanning for long-term follow-up. It combined data from existing and extended cohorts in France, the UK, and Germany, and from new cohorts assembled in Belgium, Denmark, the Netherlands, Norway, Spain, and Sweden using a common protocol. A flexible dose reconstruction approach that can accommodate collection of data from historical sources (prior to 2000) and automatically extract data from the Digital Imaging and Communications in Medicine headers of recorded images available in the Picture Archiving Communication System was developed. Individual organ dose estimates for each child were derived from Monte-Carlo-based radiation transport calculations using hybrid phantoms of different sexes and ages. To account for uncertainties due to missing input data, a simulation method that maintains correlations of doses for persons within subgroups with similar exposure attributes and simulates uncertain dose-model parameter values was used. Simulation studies to evaluate the potential impact of a range of potential confounders (e.g. underlying medical conditions, socio-economic status, missing medical procedures performed outside of participating hospitals) on risk estimates were conducted based on data from some EPI-CT countries and/or reasonable scenarios. In total, 1,170,186 patients (before censorship) were enrolled in the national cohorts. Most patients (75%) had only undergone one CT scan and 29% of all patients were aged <5 years at the time of their first CT examination. The median duration of follow-up was 8 years for the entire cohort, although this varied between countries. Overall, the follow-up accounted for nearly 10 million person-years. This study received partial funding from the European Commission 7th Framework Programme under Grant Agreement No. 269912.

Age-dependent differences in DNA damage after in vitro CT exposure

PURPOSE

Age dependent radiation sensitivity for DNA damage after in vitro blood exposure by computer tomography (CT) was investigated.

MATERIALS AND METHODS

Radiation biomarkers (dicentrics and gammaH2AX) in blood samples of newborns, children under five years and adults after sham exposure (0 mGy), low-dose (41 mGy) and high-dose (978 mGy) in vitro CT exposure were analyzed.

RESULTS

Significantly higher levels of dicentric induction were found for the single and combined newborns/children group compared to adults, by a factor of 1.48 (95% CI 1.30-1.68), after exposure to 978 mGy. Although a significant dose response for damage induction and dose-dependent repair was found, the gammaH2AX assay did not show an age-dependent increase in DNA damage in newborns/children compared to adults. This was the case for the gammaH2AX levels after repair time intervals of 30 minutes and 24 hours, after correcting for the underlying background damage. For the low dose of 41 mGy, the power of the dicentric assay was also not sufficient to detect an age-dependent effect in the sample size investigated.

CONCLUSION

A 1.5-fold increased level of dicentric aberrations is detected in newborns and children under five years after 1 Gy radiation exposure.

Site-specific Solid Cancer Mortality After Exposure to Ionizing Radiation: A Cohort Study of Workers (INWORKS)

BACKGROUND

There is considerable scientific interest in associations between protracted low-dose exposure to ionizing radiation and the occurrence of specific types of cancer.

METHODS

Associations between ionizing radiation and site-specific solid cancer mortality were examined among 308,297 nuclear workers employed in France, the United Kingdom, and the United States. Workers were monitored for external radiation exposure and follow-up encompassed 8.2 million person-years. Radiation-mortality associations were estimated using a maximum-likelihood method and using a Markov chain Monte Carlo method, the latter used to fit a hierarchical regression model to stabilize estimates of association.

RESULTS

The analysis included 17,957 deaths attributable to solid cancer, the most common being lung, prostate, and colon cancer. Using a maximum-likelihood method to quantify associations between radiation dose- and site-specific cancer, we obtained positive point estimates for oral, esophagus, stomach, colon, rectum, pancreas, peritoneum, larynx, lung, pleura, bone and connective tissue, skin, ovary, testis, and thyroid cancer; in addition, we obtained negative point estimates for cancer of the liver and gallbladder, prostate, bladder, kidney, and brain. Most of these estimated coefficients exhibited substantial imprecision. Employing a hierarchical model for stabilization had little impact on the estimated associations for the most commonly observed outcomes, but for less frequent cancer types, the stabilized estimates tended to take less extreme values and have greater precision than estimates obtained without such stabilization.

CONCLUSIONS

The results provide further evidence regarding associations between low-dose radiation exposure and cancer.

Breast Cancer Risk After Radiation Therapy for Hodgkin Lymphoma: Influence of Gonadal Hormone Exposure

BACKGROUND

Young women treated with chest radiation therapy (RT) for Hodgkin lymphoma (HL) experience a strongly increased risk of breast cancer (BC). It is unknown whether endogenous and exogenous gonadal hormones affect RT-associated BC risk.

METHODS

We conducted a nested case-control study among female 5-year HL survivors treated before age 41. Hormone exposure and HL treatment data were collected through medical records and questionnaires for 174 BC case patients and 466 control patients. Radiation dose to breast tumor location was estimated based on RT charts, simulation films, and mammography reports.

RESULTS

We observed a linear radiation dose-response curve with an adjusted excess odds ratio (EOR) of 6.1%/Gy (95% confidence interval [CI]: 2.1%-15.4%). Women with menopause <30 years (caused by high-dose procarbazine or pelvic RT) had a lower BC risk (OR, 0.13; 95% CI, 0.03-0.51) than did women with menopause ≥50 years. BC risk increased by 6.4% per additional year of post-RT intact ovarian function (P<.001). Among women with early menopause (<45 years), hormone replacement therapy (HRT) use for ≥2 years did not increase BC risk (OR, 0.86; 95% CI, 0.32-2.32), whereas this risk was nonsignificantly increased among women without early menopause (OR, 3.69; 95% CI, 0.97-14.0; P for interaction: .06). Stratification by duration of post-RT intact ovarian function or HRT use did not statistically significantly modify the radiation dose-response curve.

CONCLUSIONS

BC risk in female HL survivors increases linearly with radiation dose. HRT does not appear to increase BC risk for HL survivors with therapy-induced early menopause. There are no indications that endogenous and exogenous gonadal hormones affect the radiation dose-response relationship.

Mortality from Circulatory Diseases and other Non-Cancer Outcomes among Nuclear Workers in France, the United Kingdom and the United States (INWORKS)

Positive associations between external radiation dose and non-cancer mortality have been found in a number of published studies, primarily of populations exposed to high-dose, high-dose-rate ionizing radiation. The goal of this study was to determine whether external radiation dose was associated with non-cancer mortality in a large pooled cohort of nuclear workers exposed to low-dose radiation accumulated at low dose rates. The cohort comprised 308,297 workers from France, United Kingdom and United States. The average cumulative equivalent dose at a tissue depth of 10 mm [Hp(10)] was 25.2 mSv. In total, 22% of the cohort were deceased by the end of follow-up, with 46,029 deaths attributed to non-cancer outcomes, including 27,848 deaths attributed to circulatory diseases. Poisson regression was used to investigate the relationship between cumulative radiation dose and non-cancer mortality rates. A statistically significant association between radiation dose and all non-cancer causes of death was observed [excess relative risk per sievert (ERR/Sv) = 0.19; 90% CI: 0.07, 0.30]. This was largely driven by the association between radiation dose and mortality due to circulatory diseases (ERR/Sv = 0.22; 90% CI: 0.08, 0.37), with slightly smaller positive, but nonsignificant, point estimates for mortality due to nonmalignant respiratory disease (ERR/Sv = 0.13; 90% CI: -0.17, 0.47) and digestive disease (ERR/Sv = 0.11; 90% CI: -0.36, 0.69). The point estimate for the association between radiation dose and deaths due to external causes of death was nonsignificantly negative (ERR = -0.12; 90% CI: <-0.60, 0.45). Within circulatory disease subtypes, associations with dose were observed for mortality due to cerebrovascular disease (ERR/Sv = 0.50; 90% CI: 0.12, 0.94) and mortality due to ischemic heart disease (ERR/Sv = 0.18; 90% CI: 0.004, 0.36). The estimates of associations between radiation dose and non-cancer mortality are generally consistent with those observed in atomic bomb survivor studies. The findings of this study could be interpreted as providing further evidence that non-cancer disease risks may be increased by external radiation exposure, particularly for ischemic heart disease and cerebrovascular disease. However, heterogeneity in the estimated ERR/Sv was observed, which warrants further investigation. Further follow-up of these cohorts, with the inclusion of internal exposure information and other potential confounders associated with lifestyle factors, may prove informative, as will further work on elucidating the biological mechanisms that might cause these non-cancer effects at low doses.

Mortality from Circulatory Diseases and other Non-Cancer Outcomes among Nuclear Workers in France, the United Kingdom and the United States (INWORKS)

Positive associations between external radiation dose and non-cancer mortality have been found in a number of published studies, primarily of populations exposed to high-dose, high-dose-rate ionizing radiation. The goal of this study was to determine whether external radiation dose was associated with non-cancer mortality in a large pooled cohort of nuclear workers exposed to low-dose radiation accumulated at low dose rates. The cohort comprised 308,297 workers from France, United Kingdom and United States. The average cumulative equivalent dose at a tissue depth of 10 mm [Hp(10)] was 25.2 mSv. In total, 22% of the cohort were deceased by the end of follow-up, with 46,029 deaths attributed to non-cancer outcomes, including 27,848 deaths attributed to circulatory diseases. Poisson regression was used to investigate the relationship between cumulative radiation dose and non-cancer mortality rates. A statistically significant association between radiation dose and all non-cancer causes of death was observed [excess relative risk per sievert (ERR/Sv) = 0.19; 90% CI: 0.07, 0.30]. This was largely driven by the association between radiation dose and mortality due to circulatory diseases (ERR/Sv = 0.22; 90% CI: 0.08, 0.37), with slightly smaller positive, but nonsignificant, point estimates for mortality due to nonmalignant respiratory disease (ERR/Sv = 0.13; 90% CI: -0.17, 0.47) and digestive disease (ERR/Sv = 0.11; 90% CI: -0.36, 0.69). The point estimate for the association between radiation dose and deaths due to external causes of death was nonsignificantly negative (ERR = -0.12; 90% CI: <-0.60, 0.45). Within circulatory disease subtypes, associations with dose were observed for mortality due to cerebrovascular disease (ERR/Sv = 0.50; 90% CI: 0.12, 0.94) and mortality due to ischemic heart disease (ERR/Sv = 0.18; 90% CI: 0.004, 0.36). The estimates of associations between radiation dose and non-cancer mortality are generally consistent with those observed in atomic bomb survivor studies. The findings of this study could be interpreted as providing further evidence that non-cancer disease risks may be increased by external radiation exposure, particularly for ischemic heart disease and cerebrovascular disease. However, heterogeneity in the estimated ERR/Sv was observed, which warrants further investigation. Further follow-up of these cohorts, with the inclusion of internal exposure information and other potential confounders associated with lifestyle factors, may prove informative, as will further work on elucidating the biological mechanisms that might cause these non-cancer effects at low doses.

Investigation of DNA repair-related SNPs underlying susceptibility to papillary thyroid carcinoma reveals MGMT as a novel candidate gene in Belarusian children exposed to radiation

BACKGROUND

Genetic factors may influence an individual's sensitivity to ionising radiation and therefore modify his/her risk of developing papillary thyroid carcinoma (PTC). Previously, we reported that common single nucleotide polymorphisms (SNPs) within the DNA damage recognition gene ATM contribute to PTC risk in Belarusian children exposed to fallout from the Chernobyl power plant accident. Here we explored in the same population the contribution of a panel of DNA repair-related SNPs in genes acting downstream of ATM.

METHODS

The association of 141 SNPs located in 43 DNA repair genes was examined in 75 PTC cases and 254 controls from the Gomel region in Belarus. All subjects were younger than 15 years at the time of the Chernobyl accident. Conditional logistic regressions accounting for radiation dose were performed with PLINK using the additive allelic inheritance model, and a linkage disequilibrium (LD)-based Bonferroni correction was used for correction for multiple testing.

RESULTS

The intronic SNP rs2296675 in MGMT was associated with an increased PTC risk [per minor allele odds ratio (OR) 2.54 95% CI 1.50, 4.30, P per allele = 0.0006, P corr.= 0.05], and gene-wide association testing highlighted a possible role for ERCC5 (P Gene = 0.01) and PCNA (P Gene = 0.05) in addition to MGMT (P Gene = 0.008).

CONCLUSIONS

These findings indicate that several genes acting in distinct DNA repair mechanisms contribute to PTC risk. Further investigation is needed to decipher the functional properties of the methyltransferase encoded by MGMT and to understand how alteration of such functions may lead to the development of the most common type of thyroid cancer.

The International Nuclear Workers Study (Inworks): A Collaborative Epidemiological Study to Improve Knowledge About Health Effects of Protracted Low-Dose Exposure

INWORKS is a multinational cohort study, gathering 308 297 workers in the nuclear industry in France, the United Kingdom and the United States of America, with detailed individual monitoring data for external exposure to ionising radiation. Over a mean duration of follow-up of 27 y, the number of observed deaths was 66 632, including 17 957 deaths due to solid cancers, 1791 deaths due to haematological cancers and 27 848 deaths due to cardiovascular diseases. Mean individual cumulative external dose over the period 1945-2005 was 25 mSv. Analyses demonstrated a significant association between red bone marrow dose and the risk of leukaemia (excluding chronic lymphocytic leukaemia) and between colon dose and the risk of solid cancers. INWORKS assembled some of the strongest evidence to strengthen the scientific basis for the protection of adults from low dose, low-dose rate, exposures to ionising radiation.

Examining temporal effects on cancer risk in the international nuclear workers' study

The paper continues the series of publications from the International Nuclear Workers Study cohort that comprises 308,297 workers from France, the United Kingdom and the United States, providing 8.2 million person-years of observation from a combined follow-up period (at earliest 1944 to at latest 2005). These workers' external radiation exposures were primarily to photons, resulting in an estimated average career absorbed dose to the colon of 17.4 milligray. The association between cumulative ionizing radiation dose and cancer mortality was evaluated in general relative risk models that describe modification of the excess relative risk (ERR) per gray (Gy) by time since exposure and age at exposure. Methods analogous to a nested-case control study using conditional logistic regression of sampled risks sets were used. Outcomes included: all solid cancers, lung cancer, leukemias excluding chronic lymphocytic, acute myeloid leukemia, chronic myeloid leukemia, multiple myeloma, Hodgkin lymphoma and non-Hodgkin lymphoma. Significant risk heterogeneity was evident in chronic myeloid leukemia with time since exposure, where we observed increased ERR per Gy estimates shortly after exposure (2-10 year) and again later (20-30 years). We observed delayed effects for acute myeloid leukemia although estimates were not statistically significant. Solid cancer excess risk was restricted to exposure at age 35+ years and also diminished for exposure 30 years prior to attained age. Persistent or late effects suggest additional follow-up may inform on lifetime risks. However, cautious interpretation of results is needed due to analytical limitations and a lack of confirmatory results from other studies.

Abstract P2-06-04: Breast cancer after Hodgkin lymphoma: Influence of endogenous and exogenous gonadal hormones on the radiation dose-response relationship

Background

After chest radiotherapy (RT) for Hodgkin lymphoma (HL), women experience a dose-dependent increased breast cancer (BC) risk. It is unknown whether endogenous and exogenous gonadal hormones affect the radiation dose-response relationship.

Methods

We conducted a nested case-control study among female 5-year HL survivors treated before 41 years between 1965-2000. Data were collected through medical records and questionnaires for 174 BC cases and 466 matched controls. RT charts, simulation films and mammography reports were used to estimate the radiation dose to the location of the breast tumor.

Results

The median interval between HL and BC diagnosis was 21.9 years. 98% of BC cases had received chest RT, compared to 92% of controls. We observed a linear radiation dose-response curve with an adjusted excess odd ratio (EOR) of 5.4%/Gray (95%CI:1.8%-13.37%). Women with menopause &lt;30 years (caused by high-dose procarbazine or pelvic RT) had a lower BC risk (OR:0.13, 95%CI:0.03-0.54) than women with menopause ≥50 years. BC risk increased with 7.4% for each additional year of intact ovarian function after RT (P&lt;0.001). Among women with an early menopause (&lt;45 years), the use of hormone replacement therapy (HRT) for ≥2 years did not increase BC risk (OR:0.81, 95%CI:0.30-2.21). Endogenous and exogenous hormones did not statistically significantly modify the slope of the radiation dose-response relationship.

Conclusion

HRT use did not appear to increase BC risk in female HL survivors with a therapy-induced early menopause. Moreover, there was no evidence for interaction between RT dose and years with intact ovarian function or HRT use.

Citation Format: Krul IM, Opstal - van Winden AWJ, Aleman BMP, Janus CPM, van Eggermond AM, de Bruin ML, Hauptmann M, Krol ADG, Schaapveld M, Broeks A, Kooijman KR, Fase S, Lybeert ML, Zijlstra JM, van der Maazen RWM, Kesminiene A, Diallo I, de Vathaire F, Russell NS, van Leeuwen FE. Breast cancer after Hodgkin lymphoma: Influence of endogenous and exogenous gonadal hormones on the radiation dose-response relationship [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-06-04.

Patterns and trends of computed tomography usage in outpatients of the Brazilian public healthcare system, 2001-2011

While the patterns and trends of computed tomography (CT) are well documented in developed countries, relatively little is known about CT usage in developing countries, including Brazil. We evaluated CT usage among outpatients from the public healthcare system in Brazil (SUS), which is the unique healthcare provider to about 75% of the Brazilian population. We collected the annual number of CT procedures and type of CT examinations performed in SUS for the period 2001-2011. Age at examination was evaluated for 2008-2011. CT usage in Brazil has more than tripled during the study period, but the most striking annual increase (17.5%) was observed over the years 2008-2011. Head was the most frequently examined region for all age groups, but a decreasing trend of proportional contribution of head CT, with a simultaneous increase of abdomen/pelvis and chest CT over time was observed. CT examination for pediatric and young adult patients was about 13% of all CTs (9% if we considered age-standardized CT rates). CT usage has grown rapidly in Brazil and may still be increasing. Increased CT usage may certainly be associated with improved patient care. However, given the high frequency of pediatric and young adult CT procedures and the suggested associated cancer risk, efforts need to be undertaken to reduce unwarranted CT scans in Brazil.

Doses for post-Chernobyl epidemiological studies: are they reliable?

On 26 April 2016, thirty years will have elapsed since the occurrence of the Chernobyl accident, which has so far been the most severe in the history of the nuclear reactor industry. Numerous epidemiological studies were conducted to evaluate the possible health consequences of the accident. Since the credibility of the association between the radiation exposure and health outcome is highly dependent on the adequacy of the dosimetric quantities used in these studies, this paper makes an effort to overview the methods used to estimate individual doses and the associated uncertainties in the main analytical epidemiological studies (i.e. cohort or case-control) related to the Chernobyl accident. Based on the thorough analysis and comparison with other radiation studies, the authors conclude that individual doses for the Chernobyl analytical epidemiological studies have been calculated with a relatively high degree of reliability and well-characterized uncertainties, and that they compare favorably with many other non-Chernobyl studies. The major strengths of the Chernobyl studies are: (1) they are grounded on a large number of measurements, either performed on humans or made in the environment; and (2) extensive effort has been invested to evaluate the uncertainties associated with the dose estimates. Nevertheless, gaps in the methodology are identified and suggestions for the possible improvement of the current dose estimates are made.

European Code against Cancer 4th Edition: Medical exposures, including hormone therapy, and cancer

The 4th edition of the European Code against Cancer recommends limiting - or avoiding when possible - the use of hormone replacement therapy (HRT) because of the increased risk of cancer, nevertheless acknowledging that prescription of HRT may be indicated under certain medical conditions. Current evidence shows that HRT, generally prescribed as menopausal hormone therapy, is associated with an increased risk of cancers of the breast, endometrium, and ovary, with the risk pattern depending on factors such as the type of therapy (oestrogen-only or combined oestrogen-progestogen), duration of treatment, and initiation according to the time of menopause. Carcinogenicity has also been established for anti-neoplastic agents used in cancer therapy, immunosuppressants, oestrogen-progestogen contraceptives, and tamoxifen. Medical use of ionising radiation, an established carcinogen, can provide major health benefits; however, prudent practices need to be in place, with procedures and techniques providing the needed diagnostic information or therapeutic gain with the lowest possible radiation exposure. For pharmaceutical drugs and medical radiation exposure with convincing evidence on their carcinogenicity, health benefits have to be balanced against the risks; potential increases in long-term cancer risk should be considered in the context of the often substantial and immediate health benefits from diagnosis and/or treatment. Thus, apart from HRT, no general recommendations on reducing cancer risk were given for carcinogenic drugs and medical radiation in the 4th edition of European Code against Cancer. It is crucial that the application of these measures relies on medical expertise and thorough benefit-risk evaluation. This also pertains to cancer-preventive drugs, and self-medication with aspirin or other potential chemopreventive drugs is strongly discouraged because of the possibility of serious, potentially lethal, adverse events.

European Code against Cancer 4th Edition: Ionising and non-ionising radiation and cancer

Ionising radiation can transfer sufficient energy to ionise molecules, and this can lead to chemical changes, including DNA damage in cells. Key evidence for the carcinogenicity of ionising radiation comes from: follow-up studies of the survivors of the atomic bombings in Japan; other epidemiological studies of groups that have been exposed to radiation from medical, occupational or environmental sources; experimental animal studies; and studies of cellular responses to radiation. Considering exposure to environmental ionising radiation, inhalation of naturally occurring radon is the major source of radiation in the population - in doses orders of magnitude higher than those from nuclear power production or nuclear fallout. Indoor exposure to radon and its decay products is an important cause of lung cancer; radon may cause approximately one in ten lung cancers in Europe. Exposures to radon in buildings can be reduced via a three-step process of identifying those with potentially elevated radon levels, measuring radon levels, and reducing exposure by installation of remediation systems. In the 4th Edition of the European Code against Cancer it is therefore recommended to: "Find out if you are exposed to radiation from naturally high radon levels in your home. Take action to reduce high radon levels". Non-ionising types of radiation (those with insufficient energy to ionise molecules) - including extremely low-frequency electric and magnetic fields as well as radiofrequency electromagnetic fields - are not an established cause of cancer and are therefore not addressed in the recommendations to reduce cancer risk.

European Code against Cancer 4th Edition: Ultraviolet radiation and cancer

Ultraviolet radiation (UVR) is part of the electromagnetic spectrum emitted naturally from the sun or from artificial sources such as tanning devices. Acute skin reactions induced by UVR exposure are erythema (skin reddening), or sunburn, and the acquisition of a suntan triggered by UVR-induced DNA damage. UVR exposure is the main cause of skin cancer, including cutaneous malignant melanoma, basal-cell carcinoma, and squamous-cell carcinoma. Skin cancer is the most common cancer in fair-skinned populations, and its incidence has increased steeply over recent decades. According to estimates for 2012, about 100,000 new cases of cutaneous melanoma and about 22,000 deaths from it occurred in Europe. The main mechanisms by which UVR causes cancer are well understood. Exposure during childhood appears to be particularly harmful. Exposure to UVR is a risk factor modifiable by individuals' behaviour. Excessive exposure from natural sources can be avoided by seeking shade when the sun is strongest, by wearing appropriate clothing, and by appropriately applying sunscreens if direct sunlight is unavoidable. Exposure from artificial sources can be completely avoided by not using sunbeds. Beneficial effects of sun or UVR exposure, such as for vitamin D production, can be fully achieved while still avoiding too much sun exposure and the use of sunbeds. Taking all the scientific evidence together, the recommendation of the 4th edition of the European Code Against Cancer for ultraviolet radiation is: "Avoid too much sun, especially for children. Use sun protection. Do not use sunbeds."

Risk of cancer from occupational exposure to ionising radiation: retrospective cohort study of workers in France, the United Kingdom, and the United States (INWORKS)

STUDY QUESTION

Is protracted exposure to low doses of ionising radiation associated with an increased risk of solid cancer?

METHODS

In this cohort study, 308,297 workers in the nuclear industry from France, the United Kingdom, and the United States with detailed monitoring data for external exposure to ionising radiation were linked to death registries. Excess relative rate per Gy of radiation dose for mortality from cancer was estimated. Follow-up encompassed 8.2 million person years. Of 66,632 known deaths by the end of follow-up, 17,957 were due to solid cancers.

STUDY ANSWER AND LIMITATIONS

Results suggest a linear increase in the rate of cancer with increasing radiation exposure. The average cumulative colon dose estimated among exposed workers was 20.9 mGy (median 4.1 mGy). The estimated rate of mortality from all cancers excluding leukaemia increased with cumulative dose by 48% per Gy (90% confidence interval 20% to 79%), lagged by 10 years. Similar associations were seen for mortality from all solid cancers (47% (18% to 79%)), and within each country. The estimated association over the dose range of 0-100 mGy was similar in magnitude to that obtained over the entire dose range but less precise. Smoking and occupational asbestos exposure are potential confounders; however, exclusion of deaths from lung cancer and pleural cancer did not affect the estimated association. Despite substantial efforts to characterise the performance of the radiation dosimeters used, the possibility of measurement error remains.

WHAT THIS STUDY ADDS

The study provides a direct estimate of the association between protracted low dose exposure to ionising radiation and solid cancer mortality. Although high dose rate exposures are thought to be more dangerous than low dose rate exposures, the risk per unit of radiation dose for cancer among radiation workers was similar to estimates derived from studies of Japanese atomic bomb survivors. Quantifying the cancer risks associated with protracted radiation exposures can help strengthen the foundation for radiation protection standards.

FUNDING, COMPETING INTERESTS, DATA SHARING

Support from the US Centers for Disease Control and Prevention; Ministry of Health, Labour and Welfare of Japan; Institut de Radioprotection et de Sûreté Nucléaire; AREVA; Electricité de France; US National Institute for Occupational Safety and Health; US Department of Energy; and Public Health England. Data are maintained and kept at the International Agency for Research on Cancer.

Risk of cancer from occupational exposure to ionising radiation: retrospective cohort study of workers in France, the United Kingdom, and the United States (INWORKS)

STUDY QUESTION

Is protracted exposure to low doses of ionising radiation associated with an increased risk of solid cancer?

METHODS

In this cohort study, 308,297 workers in the nuclear industry from France, the United Kingdom, and the United States with detailed monitoring data for external exposure to ionising radiation were linked to death registries. Excess relative rate per Gy of radiation dose for mortality from cancer was estimated. Follow-up encompassed 8.2 million person years. Of 66,632 known deaths by the end of follow-up, 17,957 were due to solid cancers.

STUDY ANSWER AND LIMITATIONS

Results suggest a linear increase in the rate of cancer with increasing radiation exposure. The average cumulative colon dose estimated among exposed workers was 20.9 mGy (median 4.1 mGy). The estimated rate of mortality from all cancers excluding leukaemia increased with cumulative dose by 48% per Gy (90% confidence interval 20% to 79%), lagged by 10 years. Similar associations were seen for mortality from all solid cancers (47% (18% to 79%)), and within each country. The estimated association over the dose range of 0-100 mGy was similar in magnitude to that obtained over the entire dose range but less precise. Smoking and occupational asbestos exposure are potential confounders; however, exclusion of deaths from lung cancer and pleural cancer did not affect the estimated association. Despite substantial efforts to characterise the performance of the radiation dosimeters used, the possibility of measurement error remains.

WHAT THIS STUDY ADDS

The study provides a direct estimate of the association between protracted low dose exposure to ionising radiation and solid cancer mortality. Although high dose rate exposures are thought to be more dangerous than low dose rate exposures, the risk per unit of radiation dose for cancer among radiation workers was similar to estimates derived from studies of Japanese atomic bomb survivors. Quantifying the cancer risks associated with protracted radiation exposures can help strengthen the foundation for radiation protection standards.

FUNDING, COMPETING INTERESTS, DATA SHARING

Support from the US Centers for Disease Control and Prevention; Ministry of Health, Labour and Welfare of Japan; Institut de Radioprotection et de Sûreté Nucléaire; AREVA; Electricité de France; US National Institute for Occupational Safety and Health; US Department of Energy; and Public Health England. Data are maintained and kept at the International Agency for Research on Cancer.

EPI-CT: design, challenges and epidemiological methods of an international study on cancer risk after paediatric and young adult CT

Computed tomography (CT) has great clinical utility and its usage has increased dramatically over the years. Concerns have been raised, however, about health impacts of ionising radiation exposure from CTs, particularly in children, who have a higher risk for some radiation induced diseases. Direct estimation of the health impact of these exposures is needed, but the conduct of epidemiological studies of paediatric CT populations poses a number of challenges which, if not addressed, could invalidate the results. The aim of the present paper is to review the main challenges of a study on the health impact of paediatric CTs and how the protocol of the European collaborative study EPI-CT, coordinated by the International Agency for Research on Cancer (IARC), is designed to address them. The study, based on a common protocol, is being conducted in Belgium, Denmark, France, Germany, the Netherlands, Norway, Spain, Sweden and the United Kingdom and it has recruited over one million patients suitable for long-term prospective follow-up. Cohort accrual relies on records of participating hospital radiology departments. Basic demographic information and technical data on the CT procedure needed to estimate organ doses are being abstracted and passive follow-up is being conducted by linkage to population-based cancer and mortality registries. The main issues which may affect the validity of study results include missing doses from other radiological procedures, missing CTs, confounding by CT indication and socioeconomic status and dose reconstruction. Sub-studies are underway to evaluate their potential impact. By focusing on the issues which challenge the validity of risk estimates from CT exposures, EPI-CT will be able to address limitations of previous CT studies, thus providing reliable estimates of risk of solid tumours and leukaemia from paediatric CT exposures and scientific bases for the optimisation of paediatric CT protocols and patient protection.

EPI-CT: in vitro assessment of the applicability of the γ-H2AX-foci assay as cellular biomarker for exposure in a multicentre study of children in diagnostic radiology

PURPOSE

To conduct a feasibility study on the application of the γ-H2AX foci assay as an exposure biomarker in a prospective multicentre paediatric radiology setting.

MATERIALS AND METHODS

A set of in vitro experiments was performed to evaluate technical hurdles related to biological sample collection in a paediatric radiology setting (small blood sample volume), processing and storing of blood samples (effect of storing blood at 4°C), the reliability of foci scoring for low-doses (merge γ-H2AX/53BP1 scoring), as well as the impact of contrast agent administration as potential confounding factor. Given the exploratory nature of this study and the ethical constraints related to paediatric blood sampling, blood samples from adult volunteers were used for these experiments. In order to test the feasibility of pooling the γ-H2AX data when different centres are involved in an international multicentre study, two intercomparison studies in the low-dose range (10-500 mGy) were performed.

RESULTS

Determination of the number of X-ray induced γ-H2AX foci is feasible with one 2 ml blood sample pre- and post-computed tomography (CT) scan. Lymphocyte isolation and fixation on slides is necessary within 5 h of blood sampling to guarantee reliable results. The possible enhancement effect of contrast medium on the induction of DNA DSB in a patient study can be ruled out if radiation doses and the contrast agent concentration are within diagnostic ranges. The intercomparison studies using in vitro irradiated blood samples showed that the participating laboratories, executing successfully the γ-H2AX foci assay in lymphocytes, were able to rank blind samples in order of lowest to highest radiation dose based on mean foci/cell counts. The dose response of all intercomparison data shows that a dose point of 10 mGy could be distinguished from the sham-irradiated control (p = 0.006).

CONCLUSIONS

The results demonstrate that it is feasible to apply the γ-H2AX foci assay as a cellular biomarker of exposure in a multicentre prospective study in paediatric CT imaging after validating it in an in vivo international pilot study on paediatric patients.

Ionising radiation and risk of death from leukaemia and lymphoma in radiation-monitored workers (INWORKS): an international cohort study

BACKGROUND

There is much uncertainty about the risks of leukaemia and lymphoma after repeated or protracted low-dose radiation exposure typical of occupational, environmental, and diagnostic medical settings. We quantified associations between protracted low-dose radiation exposures and leukaemia, lymphoma, and multiple myeloma mortality among radiation-monitored adults employed in France, the UK, and the USA.

METHODS

We assembled a cohort of 308,297 radiation-monitored workers employed for at least 1 year by the Atomic Energy Commission, AREVA Nuclear Cycle, or the National Electricity Company in France, the Departments of Energy and Defence in the USA, and nuclear industry employers included in the National Registry for Radiation Workers in the UK. The cohort was followed up for a total of 8.22 million person-years. We ascertained deaths caused by leukaemia, lymphoma, and multiple myeloma. We used Poisson regression to quantify associations between estimated red bone marrow absorbed dose and leukaemia and lymphoma mortality.

FINDINGS

Doses were accrued at very low rates (mean 1.1 mGy per year, SD 2.6). The excess relative risk of leukaemia mortality (excluding chronic lymphocytic leukaemia) was 2.96 per Gy (90% CI 1.17-5.21; lagged 2 years), most notably because of an association between radiation dose and mortality from chronic myeloid leukaemia (excess relative risk per Gy 10.45, 90% CI 4.48-19.65).

INTERPRETATION

This study provides strong evidence of positive associations between protracted low-dose radiation exposure and leukaemia.

FUNDING

Centers for Disease Control and Prevention, Ministry of Health, Labour and Welfare of Japan, Institut de Radioprotection et de Sûreté Nucléaire, AREVA, Electricité de France, National Institute for Occupational Safety and Health, US Department of Energy, US Department of Health and Human Services, University of North Carolina, Public Health England.

Dose Estimation for a Study of Nuclear Workers in France, the United Kingdom and the United States of America: Methods for the International Nuclear Workers Study (INWORKS)

In the framework of the International Nuclear Workers Study conducted in France, the UK and the U.S. (INWORKS), updated and expanded methods were developed to convert recorded doses of ionizing radiation to estimates of organ doses or individual personal dose equivalent [H(p)(10)] for a total number of 308,297 workers, including 40,035 women. This approach accounts for differences in dosimeter response to predominant workplace energy and geometry of exposure and for the recently published ICRP report on dose coefficients for men and women separately. The overall mean annual individual personal dose equivalent, including zero doses, is 1.73 mSv [median = 0.42; interquartile range (IQR): 0.07, 1.59]. Associated individual organ doses were estimated. INWORKS includes workers who had potential for exposure to neutrons. Therefore, we analyzed neutron dosimetry data to identify workers potentially exposed to neutrons. We created a time-varying indicator for each worker, classifying them according to whether they had a positive recorded neutron dose and if so, whether their neutron dose ever exceeded 10% of their total external penetrating radiation dose. The number of workers flagged as being exposed to neutrons was 13% for the full cohort, with 15% of the cohort in France, 12% of the cohort in the UK and 14% in the U.S. We also used available information on in vivo and bioassay monitoring to identify workers with known depositions or suspected internal contaminations. As a result of this work, information is now available that will allow various types of sensitivity analyses.