A review of the types of childhood cancer associated with a medical X-ray examination of the pregnant mother

Fetal dose assessment in a pregnant patient with brain tumor: A comparative study of proton PBS and 3DCRT/VMAT radiation therapy techniques

PURPOSE

The treatment of brain tumors in pregnant patients poses challenges, as the out-of-field dose exposure to the fetus can potentially be harmful. A pregnant patient with prior radiation treatment was presented with a brain tumor at our clinic. This work reports on our pre-treatment study that compared fetal dose exposure between intensity-modulated proton therapy (IMPT) using pencil beam scanning (PBS) and conventional photon 3D conformal radiation therapy (3DCRT) and volumetric-modulated arc therapy (VMAT), and the subsequent pregnant patient's radiation treatment.

MATERIALS AND METHODS

Pre-treatment measurements of clinical plans, 3DCRT, VMAT, and IMPT, were conducted on a phantom. Measurements were performed using a device capable of neutron detections, closely following AAPM guidelines, TG158. For photon measurements, fetus shielding was utilized. On patient treatment days, which was determined to be proton treatment, shielding was used only during daily imaging for patient setup. Additionally, an in vivo measurement was conducted on the patient.

RESULTS

Measurements showed that IMPT delivered the lowest fetal dose, considering both photon and neutron out-of-field doses to the fetus, even when shielding was implemented for photon measurements. Additionally, the proton plans demonstrated superior treatment for the mother, a reirradiation case.

CONCLUSION

The patient was treated with proton therapy, and the baby was subsequently delivered at full term with no complications. This case study supports previous clinical findings and advocates for the expanded use of proton therapy in this patient population.

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.

Estimation of maternal and foetal risk of radiation-induced cancer from a survey of computed tomography pulmonary angiography and ventilation/perfusion lung scanning for diagnosing pulmonary embolism during pregnancy

INTRODUCTION

While there are many papers on maternal and foetal radiation doses from computed tomography pulmonary angiography (CTPA) and ventilation/perfusion (V/Q) lung scanning examinations for diagnosing pulmonary embolism in pregnant patients, few have used clinical data to examine the patient lifetime attributable risk (LAR) of different cancer types. This paper aims to estimate the cancer risk from maternal radiation doses from CTPA and V/Q examinations and associated foetal doses.

METHODS

Dosimetric data were determined for 267 pregnant patients who received CTPA and/or V/Q examinations over 8 years. Organ and foetal doses were determined using software allowing patient size variations for CTPA and using two different activity-to-organ dose conversion methods for V/Q scans. The LAR of cancer incidence was estimated using International Commission on Radiological Protection (ICRP) modelling including estimates of detriment.

RESULTS

Estimated total cancer incidence was 23 and 22 cases per 100,000 for CTPA and V/Q examinations, respectively, with detriment estimates of 18 and 20 cases. Cancer incidence was evenly divided between lung and breast cancer for CTPA with lung cancer being 80% of all cancer for V/Q. The median foetal doses were 0.03 mSv for CTPA and 0.29 mSv for V/Q. Significant differences in estimated foetal dose for V/Q scans were obtained by the two different methods used. The differences in dose between the modes of CTPA scan acquisition highlight the importance of optimisation.

CONCLUSION

Maternal cancer incidence and detriment were remarkably similar for each examination. Optimisation of examinations is critical for low-dose outcomes, particularly for CTPA examination.

Long-term neurocognitive, psychosocial, and physical outcomes after prenatal exposure to radiotherapy: a multicentre cohort study of the International Network on Cancer, Infertility, and Pregnancy

BACKGROUND

The main data available on the safety of radiation during pregnancy originate from animal studies and from studies of survivors of atomic or nuclear disasters. The effect of radiotherapy to treat maternal cancer on fetal development is uncertain. This report presents a unique cohort and aims to determine the long-term neurocognitive, psychosocial and physical outcomes of offspring of mothers treated with radiotherapy during pregnancy.

METHODS

In this international, multicentre, mixed retrospective-prospective cohort study, we recruited participants between Aug 5, 2006, and Aug 24, 2023, aged between 1·5 and 46 years, at three referral centres in Belgium, the Netherlands, and the USA. Participants were eligible if they were born from mothers treated with radiotherapy during pregnancy. Fetal radiation doses were obtained from medical records and participants were followed up at predefined ages (1·5, 3, 6, 9, 12, 15, and 18 years) and 5-yearly in adulthood, based on age at enrolment, using a neurocognitive test battery (measuring intelligence, attention, and memory), parent-reported executive function and psychosocial questionnaires, and a medical assessment. Results were compared with test-specific normative data. Linear regression models investigated associations between radiotherapy factors (fetal radiation dose, gestational age at the start and end of radiotherapy, and radiotherapy duration) and outcomes.

FINDINGS

68 maternal cases of radiotherapy during pregnancy were registered by the three participating centres, of which 61 resulted in a livebirth and were therefore eligible to participate in the child follow-up study. After excluding those who did not give consent, 43 participants born from 42 mothers treated with radiotherapy during pregnancy were included in the study (median age at first assessment 3 years [IQR 2-11]; median age at last assessment 12 years [9-18]; median number of assessments two [1-4]). 18 (42%) of the included participants were female and 25 (58%) male, and 37 (86%) were of White ethnicity. Mean neurocognitive outcomes of the entire cohort were within normal ranges. No associations were found with fetal radiation dose or timing of radiotherapy during pregnancy. Six (16%) of 38 participants with neurocognitive outcomes scored lower than one SD on at least one neurocognitive outcome, three (7%) reported chronic medical conditions (spasmophilia, spastic diplegia, and IgG deficiency), and three (7%) were diagnosed with attention-deficit hyperactivity disorder (of whom two scored lower on attention). Of ten (23%) participants with lower neurocognitive score(s), a chronic medical condition, or attention-deficit hyperactivity disorder, eight were born preterm. The remaining 33 (77%) participants showed no neurocognitive, psychosocial, or chronic physical problems.

INTERPRETATION

We show on average normal neurocognitive, psychosocial, and physical outcomes after prenatal exposure to radiotherapy. Differences in outcomes could not be explained by exposure to radiotherapy during pregnancy. These results suggest that extra-abdomino-pelvic radiotherapy exposure during pregnancy in general does not adversely affect outcomes of liveborn children. Further research with a larger sample is necessary to confirm these findings.

FUNDING

Kom Op Tegen Kanker, KWF Kankerbestrijding, Stichting Tegen Kanker, Research Foundation Flanders.

ETHICS IN RADIOLOGICAL PROTECTION FOR MEDICAL DIAGNOSIS AND TREATMENT

Publication 138 defines the ethical foundations of the ICRP System of Radiological Protection based on core values (beneficence and non-maleficence, dignity, justice, and prudence) and procedural values (accountability, transparency, and inclusiveness). The purpose of the present publication is to propose a practical application of values for medical radiological protection professions. As medicine has a long history and strong culture of ethics, this publication starts by identifying the shared values, and defines a common language between biomedical ethics and radiological protection. The core values are very similar, with the autonomy of biomedical ethics, which can be seen as a corollary of dignity, and the precautionary principle, which can be understood as the implementation of prudence. In recent years, medical education and training has emphasised the values of solidarity, honesty, and, above all, empathy. All these values are defined and interpreted in the specific context of the use of ionising radiation in medicine. For those more familiar with radiological protection, the ethical implications of their actions are described. Conversely, for those who already have a good background in ethics, this publication highlights the specificities of ionising radiation that also deserve consideration.In order to emphasise the coherence between the values involved in biomedical ethics and those involved in radiological protection, this publication proposes to combine them: dignity and autonomy; beneficence and non-maleficence; prudence and precaution; justice and solidarity; transparency, accountability, and honesty; and inclusiveness and empathy. This allows a structured review of practical situations from an ethical perspective. For the sake of both example and education, this publication proposes 21 realistic scenarios (11 in imaging procedures and 10 in radiation therapies). Sensitising questions are provided to stimulate reflection and discussion. The ultimate goal is to be able to use ethical values in clinical imaging and therapy situations. Required education and training in ethics is essential for medical radiological workers throughout their career span. An example of a framework of knowledge, skills, and competencies is proposed. In order to assist the reader in a theoretically complex subject, key messages are distributed throughout the text as fixed points that can be easily understood. Although primarily aimed at medical radiological protection professionals, this publication is also intended for authorities, patients, and the public.© 2024 ICRP. Published by SAGE.

Challenges and opportunities for proton therapy during pregnancy

During pregnancy, the use of radiation therapy for cancer treatment is often considered impossible due to the assumed associated fetal risks. However, suboptimal treatment of pregnant cancer patients and unjustifiable delay in radiation therapy until after delivery can be harmful for both patient and child. In non-pregnant patients, proton-radiation therapy is increasingly administered because of its favorable dosimetric properties compared with photon-radiation therapy. Although data on the use of pencil beam scanning proton-radiation therapy during pregnancy are scarce, different case reports and dosimetric studies have indicated a more than 10-fold reduction in fetal radiation exposure compared with photon-radiation therapy. Nonetheless, the implementation of proton-radiation therapy during pregnancy requires complex fetal dosimetry for the neutron-dominated out-of-field radiation dose and faces a lack of clinical guidelines. Further exploration and standardization of proton-radiation therapy during pregnancy will be necessary to improve radiotherapeutic management of pregnant women with cancer and further reduce risks for their offspring.

In Utero Origins of Acute Leukemia in Children

Acute leukemias, mainly consisting of acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML), comprise a major diagnostic group among hematologic cancers. Due to the early age at onset of ALL, particularly, it has long been suspected that acute leukemias of childhood may have an in utero origin. This supposition has motivated many investigations seeking direct proof of prenatal leukemogenesis, in particular, twin and "backtracking studies". The suspected in utero origin has also focused on gestation as a critical window of risk, resulting in a rich literature on prenatal risk factors for pediatric acute leukemias. In this narrative review, we recount the circumstantial and direct evidence for an in utero origin of childhood acute leukemias.

Lifetime attributable risks (LARs) of cancer in the fetus associated with maternal radiography examinations

PURPOSE

For various reasons, pregnant women are occasionally exposed to ionizing radiation during radiology examinations. In these situations, it is essential to determine the radiation dose to the fetus and any associated risks. The present study attempts to calculate the mean dose for the fetus to estimate the possible cancer induction and cancer mortality risks resulting from maternal radiography exams.

MATERIAL AND METHODS

The GATE Monte Carlo platform and a standard voxelized pregnant phantom were employed to calculate fetal radiation dose during maternal radiography exams. The data published in Biological Effects of Ionizing Radiation VII were used to convert fetal dose to lifetime attributable risks (LARs) of cancer incidence and cancer-related mortality.

RESULTS

The fetal doses and LARs of cancer incidence and cancer-related mortality for the radiographs of the chest and skull were negligible. The maximum LAR values for the lateral view of the abdomen in computed and digital radiography are 5598.29 and 2238.95 per 100,000 individuals, respectively. The computed radiography of the lateral view of the abdomen revealed the highest LAR of cancer-related mortality (2074.30 deaths for every 100,000 people).

CONCLUSION

The radiation dose incurred by the fetus due to chest and skull radiographs was minimal and unlikely to cause any abnormalities in the fetus. The discernible elevation in the lifetime attributable risk associated with cancer incidence and mortality arising from lateral computed radiography examinations of the abdomen warrants careful consideration within the realm of maternal radiography examinations.

Radiotherapy for non-cancer diseases: benefits and long-term risks

PURPOSE

The discovery of X-rays was followed by a variety of attempts to treat infectious diseases and various other non-cancer diseases with ionizing radiation, in addition to cancer. There has been a recent resurgence of interest in the use of such radiotherapy for non-cancer diseases. Non-cancer diseases for which use of radiotherapy has currently been proposed include refractory ventricular tachycardia, neurodegenerative diseases (e.g. Alzheimer's disease and dementia), and Coronavirus Disease 2019 (COVID-19) pneumonia, all with ongoing clinical studies that deliver radiation doses of 0.5-25 Gy in a single fraction or in multiple daily fractions. In addition to such non-cancer effects, historical indications predominantly used in some countries (e.g. Germany) include osteoarthritis and degenerative diseases of the bones and joints. This narrative review gives an overview of the biological rationale and ongoing preclinical and clinical studies for radiotherapy proposed for various non-cancer diseases, discusses the plausibility of the proposed biological rationale, and considers the long-term radiation risks of cancer and non-cancer diseases.

CONCLUSIONS

A growing body of evidence has suggested that radiation represents a double-edged sword, not only for cancer, but also for non-cancer diseases. At present, clinical evidence has shown some beneficial effects of radiotherapy for ventricular tachycardia, but there is little or no such evidence of radiotherapy for other newly proposed non-cancer diseases (e.g. Alzheimer's disease, COVID-19 pneumonia). Patients with ventricular tachycardia and COVID-19 pneumonia have thus far been treated with radiotherapy when they are an urgent life threat with no efficient alternative treatment, but some survivors may encounter a paradoxical situation where patients were rescued by radiotherapy but then get harmed by radiotherapy. Further studies are needed to justify the clinical use of radiotherapy for non-cancer diseases, and optimize dose to diseased tissue while minimizing dose to healthy tissue.

Radiation exposure during CT procedures in Tanzania

The aim of this study was to evaluate optimisation status during common computed tomography (CT) procedures by determining values of volume computed tomography dose index (CTDIvol) and dose-length product (DLP) per examination. Patient and exposure data were collected from the CT console during various CT procedures. The results show that variations in CTDIvol and DLP values were mainly because of differences in the techniques used. The 75th percentile values were set as the third quartile of the median CTDIvol or DLP values for all hospitals. These values of 40.9, 9.0, 9.4 and 16.2 mGy for CTDIvol were determined for head, high-resolution chest, abdomen-pelvis and lumbar spine, respectively. The corresponding DLP values for the same sequence of CT procedures were 900, 360, 487 and 721 mGy.cm, respectively. The updated results provide a basis for optimising the procedures of CT in this country.

Epidemiological and experimental evidence for radiation-induced health effects in the progeny after exposure in utero

PURPOSE

It has been known for many decades that radiation exposure of the developing embryo or fetus may cause two fundamentally different types of severe health effects: on the one hand, radiation may interfere with the normal intrauterine development, on the other hand, radiation may induce leukemia and cancer which become manifest in childhood. A large amount of epidemiological and experimental data has recently been presented which might be used to improve our understanding of underlying mechanisms and setting radiation protection standards. Yet, ecological studies in the populations exposed to increased levels of radiation in regions contaminated by radioactivity released from reactor accidents (Chernobyl, Fukushima) do not provide solid evidence which would contribute to this aim. On the other hand, well designed experimental studies demonstrated the multifactorial mechanisms which lead to different health effects after radiation exposure in utero.

CONCLUSION

There is no convincing evidence, neither from epidemiological nor experimental data of the existence of a dose threshold for developmental defects after radiation exposure in utero. This must be taken into account in the revision of rules and regulations of radiation protection in medicine.

Gender-inclusive practice in pregnancy determination for transgender, gender diverse and non-binary patients in medical imaging

In recent years, there has been an increased awareness and understanding of the varying gender identities within our society. Consequently, there has also been a need for healthcare providers to be cognizant of the unique needs of a gender-diverse population. Determining the pregnancy status of transgender, gender-diverse and non-binary patients in medical imaging settings has been poorly handled, and there is a lack of standardisation in the Australian and Aotearoa New Zealand setting. The potential risk of exposing a gender-diverse pregnant patient to ionising radiation increases the need for guidance to ensure potentially pregnant persons are not missed during screening questionnaires. This review article explores various approaches to pregnancy status determination for gender-diverse patients, recognising the complexities involved and emphasising the need for future work to establish a widely accepted solution.

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

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

Translocations are induced in hematopoietic stem cells after irradiation of fetal mice

Although mammalian fetuses have been suggested to be sensitive to radiation, an increased frequency of translocations was not observed in blood lymphocytes from atomic bomb (A-bomb) survivors who were exposed to the bomb in utero and examined as adults. Since experiments using hematopoietic cells of mice and rats confirmed this finding, it was hypothesized that either irradiated fetal hematopoietic stem cells (f-HSCs) cannot generate exchange-type chromosomal aberrations or cells bearing induced aberrations are eliminated before the animals reach adulthood. In the present study, pregnant mice (12.5-15.5 days post coitum [dpc]) were irradiated with 2 Gy of X-rays and long-term HSCs (LT-HSCs) were isolated 24 h later. Multicolor fluorescence in situ hybridization (mFISH) analysis of LT-HSC clones proliferated in vitro showed that nine out of 43 (21%) clones from fetuses and 21 out of 41 (51%) clones from mothers bore translocations. These results indicate that cells with translocations can arise in mouse f-HSCs but exist at a lower frequency than in the mothers 24 h after X-ray exposure. Thus, it seems likely that translocation-bearing f-HSCs are generated but subsequently disappear, so that the frequency of lymphocyte translocations may decrease and reach the control level by the time the animals reach adulthood.

Curative effect of cervical lifting suture combined with the improved Hayman suture in pernicious placenta previa under noninterventional conditions: A retrospective cohort study

OBJECTIVE

To propose a novel operative strategy involving cervical lifting suture (CLS) in conjunction with the improved Hayman suture (CLS-Hayman) to apply in the cesarean section of pernicious placenta previa (PPP) under noninterventional conditions and evaluate the curative effect of the CLS-Hayman operation by comparing with conventional CLS.

METHODS

A retrospective cohort study was conducted on 119 pregnant women diagnosed with PPP, including 50 cases in the CLS-Hayman group and 69 cases in the CLS group. The authors used different statistical methods to compare intraoperative bleeding, 24-h postpartum bleeding, postoperative complication rates, and uterine involution between the two groups under noninterventional conditions.

RESULTS

The median intraoperative blood loss was 800 mL in the CLS-Hayman group versus 1000 mL in the CLS group. The amount of 24-h postpartum bleeding in the CLS-Hayman group was lower than that in the CLS group. The complication rates in the two groups were 12% and 27.5%, respectively (P = 0.04). B-ultrasound or magnetic resonance imaging data showed that the uterine involution was better in the CLS-Hayman group.

CONCLUSION

The CLS-Hayman suture achieves the desired intraoperative hemostasis and also stands out for its better prevention of postpartum hemorrhage, better prognosis at follow-up, and lower complication rates.

ICRP PUBLICATION 153 Approved by the Commission in September 2022

Veterinary use of radiation in the diagnosis, management, and treatment of disease has expanded and diversified, as have the corresponding radiological protection concerns. Radiological exposure of personnel involved in veterinary procedures and, where applicable, members of the public providing assistance (e.g. owners or handlers) has always been included within the system of radiological protection. Veterinary practice is now addressed explicitly as the modern complexities associated with this practice warrant dedicated consideration, and there is a need to clarify and strengthen the application of radiological protection principles in this area. The Commission recommends that the system of radiological protection should be applied in veterinary practice principally for the protection of humans, but with explicit attention to the protection of exposed animals. Additionally, consideration should be given to the risk of potential contamination of the environment associated with applications of nuclear medicine in veterinary practice. This publication focuses primarily on justification and optimisation in veterinary practice, and sets the scene for more detailed guidance to follow in future Recommendations. It is intended for a wide-ranging audience, including radiological protection professionals, veterinary staff, students, education and training providers, and members of the public, as an introduction to radiological protection in veterinary practice.© 2022 ICRP. Published by SAGE.

The Evidence for Excess Risk of Cancer and Non-Cancer Disease at Low Doses and Dose Rates

The question of whether there are excess radiation-associated health risks at low dose is controversial. We present evidence of excess cancer risks in a number of (largely pediatrically or in utero exposed) groups exposed to low doses of radiation (<0.1 Gy). Moreover, the available data on biological mechanisms do not provide support for the idea of a low-dose threshold or hormesis for any of these endpoints. There are emerging data suggesting risks of cardiovascular disease and cataract at low doses, but this is less well established. This large body of evidence does not suggest and, indeed, is not statistically compatible with any very large threshold in dose (>10 mGy), or with possible beneficial effects from exposures. The presented data suggest that exposure to low-dose radiation causes excess cancer risks and quite possibly also excess risks of various non-cancer endpoints.

Ionizing radiation exposure during adulthood and risk of developing central nervous system tumors: systematic review and meta-analysis

Many studies on ionizing radiation (IR) exposure during childhood have shown deleterious effects on the central nervous system (CNS), however results regarding adult exposure are inconsistent, and no systematic reviews have been performed. The objectives are to synthesize the findings and draw evidence-based conclusions from epidemiological studies on the risk of benign and malignant brain and CNS tumors in humans exposed to low-to-moderate doses (< 0.5 Gy) of IR during adulthood/young adulthood. A systematic literature search of four electronic databases, supplemented by a hand search, was performed to retrieve relevant epidemiological studies published from 2000 to 2022. Pooled excess relative risk (ERRpooled) was estimated using a random effect model. Eighteen publications were included in the systematic review and twelve out of them were included in a meta-analysis. The following IR sources were considered: atomic bombs, occupational, and environmental exposures. No significant dose-risk association was found for brain/CNS tumors (ERRpooled at 100 mGy = - 0.01; 95% CI: - 0.05, 0.04). Our systematic review and meta-analysis did not show any association between exposure to low-to-moderate doses of IR and risk of CNS tumors. Further studies with histological information and precise dose assessment are needed.

Cancer risks among studies of medical diagnostic radiation exposure in early life without quantitative estimates of dose

BACKGROUND

There is accumulating evidence of excess risk of cancer in various populations exposed at acute doses below several tens of mSv or doses received over a protracted period. There is also evidence that relative risks are generally higher after radiation exposures in utero or in childhood.

METHODS AND FINDINGS

We reviewed and summarised evidence from 89 studies of cancer following medical diagnostic exposure in utero or in childhood, in which no direct estimates of radiation dose are available. In all of the populations studied exposure was to sparsely ionizing radiation (X-rays). Several of the early studies of in utero exposure exhibit modest but statistically significant excess risks of several types of childhood cancer. There is a highly significant (p < 0.0005) negative trend of odds ratio with calendar period of study, so that more recent studies tend to exhibit reduced excess risk. There is no significant inter-study heterogeneity (p > 0.3). In relation to postnatal exposure there are significant excess risks of leukaemia, brain and solid cancers, with indications of variations in risk by cancer type (p = 0.07) and type of exposure (p = 0.02), with fluoroscopy and computed tomography scans associated with the highest excess risk. However, there is highly significant inter-study heterogeneity (p < 0.01) for all cancer endpoints and all but one type of exposure, although no significant risk trend with calendar period of study.

CONCLUSIONS

Overall, this large body of data relating to medical diagnostic radiation exposure in utero provides support for an associated excess risk of childhood cancer. However, the pronounced heterogeneity in studies of postnatal diagnostic exposure, the implied uncertainty as to the meaning of summary measures, and the distinct possibilities of bias, substantially reduce the strength of the evidence from the associations we observe between radiation imaging in childhood and the subsequent risk of cancer being causally related to radiation exposure.

Low-dose radiotherapy for COVID-19 pneumonia and cancer: summary of a recent symposium and future perspectives

The lessons learned from the Coronavirus Disease 2019 (COVID-19) pandemic are numerous. Low dose radiotherapy (LDRT) was used in the pre-antibiotic era as treatment for bacterially/virally associated pneumonia. Motivated in part by these historic clinical and radiobiological data, LDRT for treatment of COVID-19-associated pneumonia was proposed in early 2020. Although there is a large body of epidemiological and experimental data pointing to effects such as cancer at low doses, there is some evidence of beneficial health effects at low doses. It has been hypothesized that low dose radiation could be combined with immune checkpoint therapy to treat cancer. We shall review here some of these old radiobiological and epidemiological data, as well as the newer data on low dose radiation and stimulated immune response and other relevant emerging data. The paper includes a summary of several oral presentations given in a Symposium on "Low dose RT for COVID and other inflammatory diseases" as part of the 67th Annual Meeting of the Radiation Research Society, held virtually 3-6 October 2021.

Age effects on radiation response: summary of a recent symposium and future perspectives

One of the principal uncertainties when estimating population risk of late effects from epidemiological data is that few radiation-exposed cohorts have been followed up to extinction. Therefore, the relative risk model has often been used to estimate radiation-associated risk and to extrapolate risk to the end of life. Epidemiological studies provide evidence that children are generally at higher risk of cancer induction than adults for a given radiation dose. However, the strength of evidence varies by cancer site and questions remain about site-specific age at exposure patterns. For solid cancers, there is a large body of evidence that excess relative risk (ERR) diminishes with increasing age at exposure. This pattern of risk is observed in the Life Span Study (LSS) as well as in other radiation-exposed populations for overall solid cancer incidence and mortality and for most site-specific solid cancers. However, there are some disparities by endpoint in the degree of variation of ERR with exposure age, with some sites (e.g., colon, lung) in the LSS incidence data showing no variation, or even increasing ERR with increasing age at exposure. The pattern of variation of excess absolute risk (EAR) with age at exposure is often similar, with EAR for solid cancers or solid cancer mortality decreasing with increasing age at exposure in the LSS. We shall review the human data from the Japanese LSS cohort, and a variety of other epidemiological data sets, including a review of types of medical diagnostic exposures, also some radiobiological animal data, all bearing on the issue of variations of radiation late-effects risk with age at exposure and with attained age. The paper includes a summary of several oral presentations given in a Symposium on "Age effects on radiation response" as part of the 67th Annual Meeting of the Radiation Research Society, held virtually on 3-6 October 2021.

Melanoma in pregnancy: Diagnosis and management in early-stage and advanced disease

Approximately one-third of women diagnosed with melanoma are of child-bearing age. The annual incidence of melanoma has risen steadily over the last 40 years, resulting in increasing numbers of women diagnosed with melanoma both during pregnancy, and post-partum. To date, there are no formal guidelines on the management of pregnancy associated melanoma (PAM), both early stage and metastatic. This article reviews the existing literature and provides a framework for the investigation and multidisciplinary management of PAM.

Chromosome aberrations among atomic-bomb survivors exposed in utero: updated analysis accounting for revised radiation doses and smoking

A previous study of peripheral blood lymphocyte translocations around age 40 among atomic-bomb survivors exposed in utero revealed no overall association with radiation dose-despite a clear association between translocations and dose among their mothers-but the data suggested an increase at doses below 100 mGy with a definite peak. That analysis of the in utero-exposed survivors did not adjust for their subsequent smoking behavior, an established cause of chromosomal aberrations, or their subsequent exposures to medical irradiation, a potential mediator. In addition, atomic-bomb survivor radiation dose estimates have subsequently been updated and refined. We therefore re-estimated the dose response using the latest DS02R1 dose estimates and adjusting for smoking as well as for city and proximal-distal location at the time of exposure to the atomic bomb. Sex of the survivor, mother's age around the time of conception, and approximate trimester of gestation at the time of exposure were also considered as explanatory variables and modifiers. Precision of the estimated dose response was slightly lower due to greater variability near zero in the updated dose estimates, but there was little change in evidence of a low-dose increase and still no suggestion of an overall increase across the entire dose range. Adjustment for smoking behavior led to a decline in background number of translocations (the dose-response intercept), but smoking did not interact with dose overall (across the entire dose range). Adjustment for medical irradiation did not alter the association between dose and translocation frequency. Sex, mother's age, and trimester were not associated with number of translocations, nor did they interact with dose overall. Interactions with dose in the low-dose range could not be evaluated because of numerical instability.

Review of the risk of cancer following low and moderate doses of sparsely ionising radiation received in early life in groups with individually estimated doses

BACKGROUND

The detrimental health effects associated with the receipt of moderate (0.1-1 Gy) and high (>1 Gy) acute doses of sparsely ionising radiation are well established from human epidemiological studies. There is accumulating direct evidence of excess risk of cancer in a number of populations exposed at lower acute doses or doses received over a protracted period. There is evidence that relative risks are generally higher after radiation exposures in utero or in childhood.

METHODS AND FINDINGS

We reviewed and summarised evidence from 60 studies of cancer or benign neoplasms following low- or moderate-level exposure in utero or in childhood from medical and environmental sources. In most of the populations studied the exposure was predominantly to sparsely ionising radiation, such as X-rays and gamma-rays. There were significant (p < 0.001) excess risks for all cancers, and particularly large excess relative risks were observed for brain/CNS tumours, thyroid cancer (including nodules) and leukaemia.

CONCLUSIONS

Overall, the totality of this large body of data relating to in utero and childhood exposure provides support for the existence of excess cancer and benign neoplasm risk associated with radiation doses < 0.1 Gy, and for certain groups exposed to natural background radiation, to fallout and medical X-rays in utero, at about 0.02 Gy.

Cancer risk following low doses of ionising radiation - Current epidemiological evidence and implications for radiological protection

Recent studies suggest that every year worldwide about a million patients might be exposed to doses of the order of 100 mGy of low-LET radiation, due to recurrent application of radioimaging procedures. This paper presents a synthesis of recent epidemiological evidence on radiation-related cancer risks from low-LET radiation doses of this magnitude. Evidence from pooled analyses and meta-analyses also involving epidemiological studies that, individually, do not find statistically significant radiation-related cancer risks is reviewed, and evidence from additional and more recent epidemiological studies of radiation exposures indicating excess cancer risks is also summarized. Cohorts discussed in the present paper include Japanese atomic bomb survivors, nuclear workers, patients exposed for medical purposes, and populations exposed environmentally to natural background radiation or radioactive contamination. Taken together, the overall evidence summarized here is based on studies including several million individuals, many of them followed-up for more than half a century. In summary, substantial evidence was found from epidemiological studies of exposed groups of humans that ionizing radiation causes cancer at acute and protracted doses above 100 mGy, and growing evidence for doses below 100 mGy. The significant radiation-related solid cancer risks observed at doses of several 100 mGy of protracted exposures (observed, for example, among nuclear workers) demonstrate that doses accumulated over many years at low dose rates do cause stochastic health effects. On this basis, it can be concluded that doses of the order of 100 mGy from recurrent application of medical imaging procedures involving ionizing radiation are of concern, from the viewpoint of radiological protection.