Risk factors for central nervous system tumors in children: New findings from a case-control study

Relationship between parental exposure to radiofrequency electromagnetic fields and primarily hematopoietic neoplasms (lymphoma, leukemia) and tumors in the central nervous system in children: a systematic review

Low-frequency electromagnetic fields have grown exponentially in recent years due to technological development and modernization. The World Health Organization (WHO)/International Agency for Research on Cancer (IARC) has classified radiofrequency electromagnetic fields (RF-EMFs) as possibly carcinogenic to humans (Group 2B), and recent studies have investigated the association between exposure to electromagnetic fields in parents and possible health effects in children, especially the development of tumours of the central nervous system (CNS). The objective of this systematic review was to collate all evidence on the relationship between parental occupational exposure to electromagnetic fields and the development of CNS cancer in children and to evaluate this association. This review was prepared according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, Embase, and Web of Science were searched from January 1990 to April 2021. The search was conducted using the following search string: "occupational" AND "child" AND "electromagnetic" AND "cancer". Seventeen articles met our inclusion criteria: 13 case-control studies, two cohort studies, and 2 meta-analyses. Most of the studies showed several methodological weaknesses that limited their results. Due to a lack of consistency regarding the outcome as well as the heterogeneity in the reviewed studies, the body of evidence for the effects of parental exposure to electromagnetic fields is not clear. Methodological heterogeneity in the way that studies were conducted could be responsible for the lack of consistency in the findings. Overall, the body of evidence allows no conclusion on the relationship between parental exposure to electromagnetic fields and the occurrence of CNS tumours in children.

Registration, incidence patterns, and survival trends of central nervous system tumors among children in Germany 1980-2019: An analysis of 40 years based on data from the German Childhood Cancer Registry

BACKGROUND

Tumors of the central nervous system (CNS) are the second most common type of pediatric cancer in Germany. We aimed to describe registration practice, incidence, and survival patterns for childhood CNS tumors in Germany for the past 40 years.

PROCEDURE

Including all CNS tumor cases in children diagnosed at ages 0-14 years registered at the German Childhood Cancer Registry (GCCR) in 1980-2019 (for survival analysis 1980-2016), we calculated age-specific and age-standardized incidence rates (ASIR) over time, average annual percentage changes (AAPC), and 1- and 5-year overall survival.

RESULTS

While we observed a pronounced increase in ASIR after the establishment of the GCCR during the 1980s, ASIR for all pediatric CNS tumors combined continued to increase markedly from 28.6 per million in 1990-1999 to 43.3 in 2010-2019 (AAPC = 2.7% in 1991-2010, AAPC = 0.3% in 2010-2019). The 5-year overall survival from CNS tumors improved from 63% in the 1980s, 70% in the 1990s to 79% in 2010-2016. These improvements have occurred across all age groups. Children diagnosed with ependymomas and choroid plexus tumors experienced the strongest increase (from 54% to 81%).

CONCLUSIONS

Observed increases in incidence rates for pediatric CNS tumors are likely only partially caused by actual increasing case numbers. The majority is a function of improved registration and, to a minor extent, improvements in diagnostics. Survival from pediatric CNS tumors has, by and large, improved consistently, leading to a growing population of childhood cancer survivors with diverse health biographies and risk of lifelong adverse impact on health and wellbeing.

Socio-demographic and antenatal risk factors of brain tumor in children and young people: A matched case-control study from Karachi, Pakistan

Background

Brain tumors are a common cause of morbidity, disability, cognitive deterioration and mortality in children, even after treatment. Little is know about the specific causes. The study aimed to assess potential socio-demographic and antenatal factors in primary brain tumor (PBTs) in children and young people (CYP) in Karachi, Pakistan.

Designs and methods

A single center hospital based matched case control study in Karachi, Pakistan. Cases were defined as CYP aged between 5 and 21 years with any histological type and grade of primary brain tumor of any histology, stage or grade. Data were collected from parents of 244 patients at the selected center between 2017 and 2021 via telephonic interview. Controls were 5-21 years old CYP admitted with non-oncological diagnoses matched on age and sex. Matched Odds Ratios for predictors of brain tumor in children were derived. Those of statistical significance were included in a multivariable logistic regression model.

Results

In the adjusted model, lower paternal education (matched adjusted odds ratio (maOR) 2.46; 95% CI 1.09-5.55), higher household monthly income (maOR 3.4; 95% CI 1.1-10.2), antenatal paternal use of addictive substances (maOR 19.5; 95% CI 2.1-179.8), and antenatal maternal use of analgesics during pregnancy (maOR 3.0; 95% CI 1.2-7.9) were all independently predictive of brain tumors.

Conclusion

This matched case-control study found novel associations between maternal use of analgesics, paternal use of addictive substances, higher household income, and lower paternal education and Primary Brain Tumors in Children and Young People. Longitudinal multicenter studies will be required to test these associations prospectively.

The comparative burden of brain and central nervous system cancers from 1990 to 2019 between China and the United States and predicting the future burden

Background

Brain and central nervous system (CNS) cancers represent a major source of cancer burden in China and the United States. Comparing the two countries' epidemiological features for brain and CNS cancers can help plan interventions and draw lessons.

Methods

Data were extracted from the Global Burden of Disease repository. The average annual percentage change (AAPC) and relative risks of cancer burdens were calculated using joinpoint regression analysis and age-period-cohort (APC) models, respectively. Moreover, a Bayesian APC model was employed to predict the disease burden over the next decade.

Results

From 1990 to 2019, the number of incidences, deaths, and disability-adjusted life-years (DALYs) increased in China and the US, with a larger increase in China. Age-standardized incidence rates in China and the United States have shown an increasing trend over the past three decades, with AAPCs of 0.84 and 0.16%, respectively. However, the rates of age-standardized mortality and age-standardized DALYs decreased in both countries, with a greater decrease in China. Overall, age trends in cancer burden were similar for males and females, with two peaks in the childhood and elderly groups, respectively. The period and cohort effects on incidence showed an overall increasing trend in China and limited change in the US. However, the period effects for mortality and DALY were decreasing in both countries, while the cohort effects tended to increase and then decrease. Moreover, we predicted that the cancer burdens would continue to rise in China over the next decade.

Conclusion

The burden of brain and CNS cancers is substantial and will continue to increase in China. Comprehensive policy and control measures need to be implemented to reduce the burden.

Environmental Risk Factors for Childhood Cancer in an Era of Global Climate Change: A Scoping Review

INTRODUCTION

Contemporary research about environmental risk factors in an era of global climate change to inform childhood cancer prevention efforts is disjointed. Planetary pediatric providers need to establish a better understanding of how the postnatal environment influences childhood cancer. Authors conducted a scoping review of recent scientific literature with the aim of understanding the environmental risk factors for childhood cancer.

METHOD

Ovid Medline, CINAHL, and Scopus databases were searched with results limited to the English language with publication years 2010-2021. Two independent reviewers screened 771 abstracts and excluded 659 abstracts and 65 full-text articles on the basis of predefinedcriteria.

RESULTS

The scoping review identified 47 studies about environmental risk factors for childhood cancer with mixed results and limited consensus in four main categories, including air pollution, chemical exposures, radiation, and residential location.

DISCUSSION

Research by collaborative international groups of planetary health researchers about environmental risk factors is needed to inform global health policy for childhood cancer prevention efforts.

A Comparison of Epidemiological Characteristics of Central Nervous System Tumours in China and Globally from 1990 to 2019

BACKGROUND

Despite their great disease burden, there have been few studies on the epidemiology of central nervous system tumours (CNSTs) in China. We used the latest data updated by GBD to analyse the trends of incidence, mortality, and disability-adjusted life years (DALYs) for CNSTs in China versus globally.

METHODS

Epidemiological data on CNSTs were extracted from GBD 2019. We used Joinpoint regression analysis to calculate the magnitude and direction of the trends and the age-period-cohort method to analyse the age, period, and cohort effects of the trend.

RESULTS

From 1990 to 2019, the 106.52% increase in Chinese incident cases was higher than the global increase (94.35%). The 67.32% increase in cancer deaths and 16.03% increase in DALYs were lower than the global increases (cancer death: 76.36%; DALYs: 40.06%). The age-standardized incidence rates (ASIRs) in China were higher than the global ASIRs, and the increase in China was higher than that globally. Although the age-standardized mortality rates and age-standardized DALY rates in China were higher, their increases in China were less than those globally. Both in China and globally, the number and incidence, mortality, and DALYs by age group showed a bimodal distribution (younger than 5 years and older), and the peak in the older age group showed a backwards trend. The proportion of incident cases, cancer deaths, and DALYs also increased in the older age group. In the age-period-cohort model, the local drifts in the older age group were above zero.

CONCLUSIONS

The burden of CNSTs is very serious in China, and we should pay attention to the key populations, early diagnosis technology, improvements in medical technology, and ways to reduce medical costs. We believe our results could help policymakers allocate resources efficiently to reduce the burden of CNSTs.

The need for a central brain tumor registry in Africa: A review of central nervous system tumors in Africa from 1960 to 2017

Background

Central nervous system (CNS) tumors pose a substantial health problem. Although data on specific time periods and regions of Africa have been previously reported, no study has yet to provide a systematic review of CNS tumors for the entire continent of Africa. This study aims to analyze the frequency of CNS tumors in Africa from 1960 to 2017.

Methods

A comprehensive literature search on CNS tumors in Africa was performed using multiple online scientific databases. The following keywords were queried in combination with the phrase "CNS tumors in Africa": incidence, frequency, epidemiology, prevalence, brain, and cancer. A total of 26 articles met the inclusion criteria. Each selected article reported incidence and mortality rates from different regions of Africa in a time period between 1960 and 2017. SPSS21 statistical software was used to analyze the data.

Results

Nigeria, Egypt, and Uganda were found to have the most of the cases of CNS tumors in Africa. Males made up 54% of the 5902 cases per 100 000 population. The most common CNS tumors found were astrocytoma (24.70%), meningioma (22.22%), pituitary adenoma (8.4%), medulloblastoma (4.26%), craniopharyngioma (4.07%), and other not specified (25.17%).

Conclusions

Given the large population of Africa, the total reported cases may be underestimated when compared with other continents due to the lack of a central brain tumor registry in Africa. A comprehensive knowledge of CNS tumors in Africa is critical to population-based research and improving the current healthcare system.

Socioeconomic differences in the risk of childhood central nervous system tumors in Denmark: a nationwide register-based case-control study

PURPOSE

Differences in the risk of childhood central nervous system (CNS) tumors by socioeconomic status (SES) may enhance etiologic insights. We conducted a nationwide register-based case-control study to evaluate socioeconomic differences in the risk of childhood CNS tumors in Denmark and examined whether associations varied by different SES measures, time points of assessment, specific tumor types, and age at diagnosis.

METHODS

We identified all children born between 1981 and 2013 and diagnosed with a CNS tumor at ages 0-19 years (n = 1,273) from the Danish Cancer Registry and sampled four individually matched controls per case (n  = 5,086). We used conditional logistic regression models to estimate associations with individual-level and neighborhood-level socioeconomic measures.

RESULTS

We observed elevated risks of ependymoma and embryonal CNS tumors in association with higher parental education (odds ratios (ORs) of 1.6-2.1 for maternal or paternal high education and ependymoma) and higher risk of all tumor types in association with higher maternal income, e.g., OR  1.93; 95% CI 1.05-3.52 for high versus low income for astrocytoma and other gliomas. Associations were often stronger in children diagnosed at ages 5-19 years. We found little evidence for an association with neighborhood SES.

CONCLUSION

This large nationwide register study with minimal risk of bias showed that having parents with higher educational level and a mother with higher income was associated with a higher risk of childhood CNS tumors. Bias or under-ascertainment of cases among families with low income or basic education is unlikely to explain our findings.

Bayesian spatial modelling of childhood cancer incidence in Switzerland using exact point data: a nationwide study during 1985-2015

BACKGROUND

The aetiology of most childhood cancers is largely unknown. Spatially varying environmental factors such as traffic-related air pollution, background radiation and agricultural pesticides might contribute to the development of childhood cancer. This study is the first investigation of the spatial disease mapping of childhood cancers using exact geocodes of place of residence.

METHODS

We included 5947 children diagnosed with cancer in Switzerland during 1985-2015 at 0-15 years of age from the Swiss Childhood Cancer Registry. We modelled cancer risk using log-Gaussian Cox processes and indirect standardisation to adjust for age and year of diagnosis. We examined whether the spatial variation of risk can be explained by modelled ambient air concentration of NO2, modelled exposure to background ionising radiation, area-based socio-economic position (SEP), linguistic region, duration in years of general cancer registration in the canton or degree of urbanisation.

RESULTS

For all childhood cancers combined, the posterior median relative risk (RR), compared to the national level, varied by location from 0.83 to 1.13 (min to max). Corresponding ranges were 0.96 to 1.09 for leukaemia, 0.90 to 1.13 for lymphoma, and 0.82 to 1.23 for central nervous system (CNS) tumours. The covariates considered explained 72% of the observed spatial variation for all cancers, 81% for leukaemia, 82% for lymphoma and 64% for CNS tumours. There was weak evidence of an association of CNS tumour incidence with modelled exposure to background ionising radiation (RR per SD difference 1.17; 0.98-1.40) and with SEP (1.6; 1.00-1.13).

CONCLUSION

Of the investigated diagnostic groups, childhood CNS tumours showed the largest spatial variation. The selected covariates only partially explained the observed variation of CNS tumours suggesting that other environmental factors also play a role.

Birth seasonality of childhood central nervous system tumors: Analysis of primary data from 16 Southern-Eastern European population-based registries

Season of birth, a surrogate of seasonal variation of environmental exposures, has been associated with increased risk of several cancers. In the context of a Southern-Eastern Europe (SEE) consortium, we explored the potential association of birth seasonality with childhood (0-14 years) central nervous system (CNS) tumors. Primary CNS tumor cases (n = 6,014) were retrieved from 16 population-based SEE registries (1983-2015). Poisson regression and meta-analyses on birth season were performed in nine countries with available live birth data (n = 4,987). Subanalyses by birth month, age, gender and principal histology were also conducted. Children born during winter were at a slightly increased risk of developing a CNS tumor overall [incidence rate ratio (IRR): 1.06, 95% confidence intervals (CI): 0.99-1.14], and of embryonal histology specifically (IRR: 1.13, 95% CI: 1.01-1.27). The winter peak of embryonal tumors was higher among boys (IRR: 1.24, 95% CI: 1.05-1.46), especially during the first 4 years of life (IRR: 1.33, 95% CI: 1.03-1.71). In contrast, boys <5 years born during summer seemed to be at a lower risk of embryonal tumors (IRR: 0.73, 95% CI: 0.54-0.99). A clustering of astrocytomas was also found among girls (0-14 years) born during spring (IRR: 1.23, 95% CI: 1.03-1.46). Although the present exploratory results are by no means definitive, they provide some indications for age-, gender- and histology-related seasonal variations of CNS tumors. Expansion of registration and linkage with cytogenetic reports could refine if birth seasonality is causally associated with CNS tumors and shed light into the complex pathophysiology of this lethal disease.

Pediatric glioma and medulloblastoma risk and population demographics: a Poisson regression analysis

Background

The incidence of pediatric brain tumors varies by race and ethnicity, but these relationships may be confounded by socioeconomic status (SES). In this study, the Surveillance, Epidemiology, and End Results Program (SEER) database was evaluated for associations between race/ethnicity and pediatric glioma and medulloblastoma risk with adjustment for SES.

Methods

Pediatric glioma and medulloblastoma cases from the SEER database (years: 2000–2016) were included. Differences in incidence rates by ethnicity, sex, age, and SES-related factors were evaluated by calculation of age-adjusted incidence rates (AAIRs) and annual percent change (APC). SES-related factors (percentage without less than high school graduation, median household income, and percentage foreign-born) were derived from the census at the county-level (year: 2000). Multivariable Poisson regression models with adjustment for selected covariates were constructed to evaluate risk factors.

Results

The highest AAIRs of pediatric glioma were observed among non-Hispanic Whites (AAIR: 2.91 per 100 000, 95%-CI: 2.84–2.99). An increasing incidence of pediatric glioma by calendar time was observed among non-Hispanic Whites and non-Hispanic Blacks (APC: 0.97%, 95%-CI: 0.28–1.68 and APC: 1.59%, 95%-CI: 0.03–3.18, respectively). Hispanic and non-Hispanic Black race/ethnicity was associated with lower risk when compared with non-Hispanic White (incidence rate ratios [IRRs]: 0.66, 95%-CI: 0.63–0.70; and 0.69, 95%-CI: 0.65–0.74, respectively). For medulloblastoma, the highest AAIR was observed for non-Hispanic Whites with a positive APC (1.52%, 95%-CI: 0.15–2.91). Hispanics and non-Hispanic Blacks had statistically significant lower IRRs compared with non-Hispanic Whites (IRRs: 0.83, 95%-CI: 0.73–0.94; and 0.72, 95%-CI: 0.59–0.87, respectively).

Conclusion

Non-Hispanic White race/ethnicity was associated with higher pediatric glioma and medulloblastoma IRRs in models with adjustments for SES.

Methodological approaches to the study of cancer risk in the vicinity of pollution sources: the experience of a population-based case-control study of childhood cancer

Background

Environmental exposures are related to the risk of some types of cancer, and children are the most vulnerable group of people. This study seeks to present the methodological approaches used in the papers of our group about risk of childhood cancers in the vicinity of pollution sources (industrial and urban sites). A population-based case–control study of incident childhood cancers in Spain and their relationship with residential proximity to industrial and urban areas was designed. Two methodological approaches using mixed multiple unconditional logistic regression models to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs) were developed: (a) “near vs. far” analysis, where possible excess risks of cancers in children living near (“near”) versus those living far (“far”) from industrial and urban areas were assessed; and (b) “risk gradient” analysis, where the risk gradient in the vicinity of industries was assessed. For each one of the two approaches, three strategies of analysis were implemented: “joint”, “stratified”, and “individualized” analysis. Incident cases were obtained from the Spanish Registry of Childhood Cancer (between 1996 and 2011).

Results

Applying this methodology, associations between proximity (≤ 2 km) to specific industrial and urban zones and risk (OR; 95% CI) of leukemias (1.31; 1.04–1.65 for industrial areas, and 1.28; 1.00–1.53 for urban areas), neuroblastoma (2.12; 1.18–3.83 for both industrial and urban areas), and renal (2.02; 1.16–3.52 for industrial areas) and bone (4.02; 1.73–9.34 for urban areas) tumors have been suggested.

Conclusions

The two methodological approaches were used as a very useful and flexible tool to analyze the excess risk of childhood cancers in the vicinity of industrial and urban areas, which can be extrapolated and generalized to other cancers and chronic diseases, and adapted to other types of pollution sources.

Circular RNA expression profiles during the differentiation of mouse neural stem cells

Background

Circular RNAs (circRNAs) have recently been found to be expressed in human brain tissue, and many lines ofevidence indicate that circRNAs play regulatory roles in neurodevelopment. Proliferation and differentiation of neural stem cells (NSCs) are critical parts during development of central nervous system (CNS).To date, there have been no reports ofcircRNA expression profiles during the differentiation of mouse NSCs. We hypothesizethat circRNAs mayregulate gene expression in the proliferation anddifferentiation of NSCs.

Results

In this study, we obtained NSCs from the wild-type C57BL/6 J mouse fetal cerebral cortex. We extracted total RNA from NSCs in different differentiation stagesand then performed RNA-seq. By analyzing the RNA-Seq data, we found 37circRNAs and 4182 mRNAs differentially expressedduringthe NSC differentiation. Gene Ontology (GO) enrichment analysis of thecognate linear genes of these circRNAsrevealed that some enriched GO terms were related to neural activity. Furthermore, we performed a co-expression network analysis of these differentially expressed circRNAs and mRNAs. The result suggested a stronger GO enrichmentin neural features for both the cognate linear genes of circRNAs and differentially expressed mRNAs.

Conclusion

We performed the first circRNA investigation during the differentiation of mouse NSCs. Wefound that12 circRNAs might have regulatory roles duringthe NSC differentiation, indicating that circRNAs might be modulated during NSC differentiation.Our network analysis suggested the possible complex circRNA-mRNA mechanisms during differentiation, and future experimental workis need to validate these possible mechanisms.

Electronic supplementary material

The online version of this article (10.1186/s12918-018-0651-1) contains supplementary material, which is available to authorized users.

Childhood leukaemia risk and residential proximity to busy roads

BACKGROUND

Current evidence suggests that childhood leukaemia can be associated with residential traffic exposure; nevertheless, more results are needed to support this conclusion.

OBJECTIVES

To ascertain the possible effects of residential proximity to road traffic on childhood leukaemia, taking into account traffic density, road proximity and the type of leukaemia (acute lymphoid leukaemia or acute myeloid leukaemia).

METHODS

We conducted a population-based case-control study of childhood leukaemia in Spain, covering the period 1990-2011. It included 1061 incidence cases gathered from the Spanish National Childhood Cancer Registry and those Autonomous Regions with 100% coverage, and 6447 controls, individually matched by year of birth, sex and autonomous region of residence. Distances were computed from the respective participant's residential locations to the different types of roads and four different buffers. Using logistic regression, odds ratios (ORs) and 95% confidence intervals (95%CIs), were calculated for four different categories of distance to roads.

RESULTS

Cases of childhood leukaemia had more than three-fold increased odds of living at <50 m of the busiest motorways compared to controls (OR = 2.90; 95%CI = 1.30-6.49). The estimates for acute lymphoid leukaemia (ALL) were slightly higher (OR = 2.95; 95%CI = 1.22-7.14), while estimates for cases with the same address at birth and at diagnosis were lower (OR = 2.40; 95%CI = 0.70-8.30).

CONCLUSIONS

Our study agrees with the literature and furnishes some evidence that living near a busy motorway could be a risk factor for childhood leukaemia.

The association between high birth weight and the risks of childhood CNS tumors and leukemia: an analysis of a US case-control study in an epidemiological database

Background

High birth weight (BW), 4000 g or larger, is an established risk factor for childhood leukemia. However, its association with central nervous system (CNS) tumor risk is yet unclear. The present study examined it, analyzing data obtained from a case-control study conducted among three states from the US. The association with childhood leukemia risk was also further examined.

Methods

In this study, a data set provided by the Comprehensive Epidemiologic Data Resource was analyzed with an official permission. The original case-control study was conducted to examine the association between paternal preconception exposure to ionizing radiation and childhood cancer risk. Cases with childhood cancer were mainly ascertained from local hospitals, and controls were selected, matched with birth year (1-year category), county of residence, sex, ethnicity and maternal age (+/−2 years). Since the ID numbers were unavailable, conventional logistic analyses were conducted adjusting for those matching variables except for the county of residence. In addition to those variables, gestational age, age at diagnosis and study sites as covariables were included in the logistic models.

Results

Analyzed subjects were 72 CNS tumor cases, 124 leukemia cases and 822 controls born from 1945 to 1989. The odds ratios (ORs) of CNS tumor risk for children with low BWs (<2500 g) and high BWs (>4000 g) were 2.0 (95% confidence interval [CI]) = 0.7, 5.9) and 2.5 (95%CI = 1.2, 5.2)], respectively. When high-BW children were restricted to those who were large for gestational age (LGA), the OR for high-BW children remained similar (OR = 2.7; 95%CI = 1.1, 6.2). On the other hand, the ORs of leukemia risk for children with low and high BWs were 0.8 (95%CI = 0.2, 3.0) and 1.4 (95%CI = 0.7, 2.6), respectively. In the normal range of BW (2500–4000 g), higher BW was positively associated with CNS tumor risk (beta = 0.0011, p for trend = 0.012). However, the association with leukemia risk was not significant (beta = −0.0002, p for trend = 0.475).

Conclusion

High-BW and LGA children had an elevated childhood CNS tumor risk. In the normal BW range, the BW itself was positively related to CNS tumor risk. No significant association between BW and childhood leukemia risk was observed in this study.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3681-y) contains supplementary material, which is available to authorized users.