Maternal and perinatal risk factors for childhood cancer: record linkage study

Risk factors for childhood brain tumours: A systematic review and meta-analysis of observational studies from 1976 to 2022

BACKGROUND

Childhood brain tumours (CBTs) are the leading cause of cancer death in children under the age of 20 years globally. Though the aetiology of CBT remains poorly understood, it is thought to be multifactorial. We aimed to synthesize potential risk factors for CBT to inform primary prevention.

METHODS

We conducted a systematic review and meta-analysis of epidemiological studies indexed in the PubMed, Web of Science, and Embase databases from the start of those resources through 27 July 2023. We included data from case-control or cohort studies that reported effect estimates for each risk factor around the time of conception, during pregnancy and/or during post-natal period. Random effects meta-analysis was used to estimate summary effect sizes (ES) and 95% confidence intervals (CIs). We also quantified heterogeneity (I2) across studies.

FINDINGS

A total of 4040 studies were identified, of which 181 studies (85 case-control and 96 cohort studies) met our criteria for inclusion. Of all eligible studies, 50% (n = 91) were conducted in Europe, 32% (n = 57) in North America, 9% (n = 16) in Australia, 8% (n = 15) in Asia, 1% (n = 2) in South America, and none in Africa. We found associations for some modifiable risk factors including childhood domestic exposures to insecticides (ES 1.44, 95% CI 1.20-1.73) and herbicides (ES 2.38, 95% CI 1.31-4.33). Maternal domestic exposure to insecticides (ES 1.45, 95% CI 1.09-1.94), maternal consumption of cured meat (ES 1.51, 95% CI 1.05-2.17) and coffee ≥ 2 cups/day (ES 1.45, 95% 95% CI 1.07-1.95) during pregnancy, and maternal exposure to benzene (ES 2.22; 95% CI 1.01-4.88) before conception were associated with CBTs in case-control studies. Also, paternal occupational exposure to pesticides (ES 1.48, 95% CI 1.23-1.77) and benzene (ES 1.74, 95% CI 1.10-2.76) before conception and during pregnancy were associated in case-control studies and in combined analysis. On the other hand, assisted reproductive technology (ART) (ES 1.32, 95% CI 1.05-1.67), caesarean section (CS) (ES 1.12, 95% CI 1.01-1.25), paternal occupational exposure to paint before conception (ES 1.56, 95% CI 1.02-2.40) and maternal smoking > 10 cigarettes per day during pregnancy (ES 1.18, 95% CI 1.00-1.40) were associated with CBT in cohort studies. Maternal intake of vitamins and folic acid during pregnancy was inversely associated in cohort studies. Hormonal/infertility treatment, breastfeeding, child day-care attendance, maternal exposure to electric heated waterbed, tea and alcohol consumption during pregnancy were among those not associated with CBT in both case-control and cohort studies.

CONCLUSION

Our results should be interpreted with caution, especially as most associations between risk factors and CBT were discordant between cohort and case-control studies. At present, it is premature for any CBT to define specific primary prevention guidelines.

Preeclampsia, antihypertensive medication use in pregnancy and risk of childhood cancer in offspring

PURPOSE

Preeclampsia is a serious pregnancy complication that presents a significant risk to both the mother and the fetus. Preeclampsia and medications associated with its treatment are potentially linked to increased childhood cancer risk. Therefore, we examined the association between preeclampsia, antihypertensive medications, and childhood cancer in offspring.

METHODS

Cases (n = 6,420) and controls (n = 160,484) were obtained from Danish national registries. We performed conditional logistic regression analyses to estimate the association between preeclampsia and childhood cancer risk, and examined the effects of antihypertensive medication use in pregnancy in relation to childhood cancer risk in the offspring with adjustment for relevant covariates.

RESULTS

We observed an increased risk of acute lymphoblastic leukemia (ALL) among those whose mothers had preeclampsia (OR = 1.36, 95% CI 1.03, 1.79), especially for severe preeclampsia (OR = 2.36, 95% CI 1.37, 4.08). We also estimated an increased cancer risk in children born to mothers who were prescribed diuretics during pregnancy [OR = 2.09, 95% confidence interval (CI) 1.39, 3.14]. Intake of other antihypertensive medications was not associated with childhood cancer (OR = 0.78, 95% CI 0.50, 1.23). Among women who did not take diuretics in pregnancy, preeclampsia was associated with neuroblastoma (OR = 2.22, 95% CI 1.08, 4.55).

CONCLUSION

Our findings suggested an increased risk for certain types of cancer in the offspring of mothers with preeclampsia and an increased risk of cancer with diuretic intake during pregnancy.

Risk factors for tumors or leukemia development in the first two years of life

OBJECTIVES

The objective of this study was to determine the incidence of neoplastic diseases and associated risk factors in the early stages of life.

METHODS

Data were retrospectively assessed in 730,000 live births between 2000 and 2019. The occurrence of tumors was monitored in the neonatal, infant (1-12 months), and toddler (13-24 months) periods. Risk factors were divided into demographic, internal, and environmental factors. The control group consisted of subjects in the same age category without oncological diseases.

RESULTS

A total of 452 neoplastic diseases were diagnosed in the study sample. In total, 24% (110/452) manifested during the neonatal period, 45% (203/452) in infants, and 31% (139/452) at the age of 13-24 months. Any genetic disease (OR 26.68; 95% CI 7.64-93.12) and medications used by the mother (OR 3.07; 95% CI 1.32-7.15) were identified as risk factors. Without adjustment for all factors, asphyxia in the first minute, a younger age of the mother, lower pregnancy, and the presence of a congenital defect manifested themselves as risk factors.

CONCLUSIONS

The highest risk factors for the development of early childhood tumors were identified as with medications used by the mother before or during pregnancy and genetic diseases.

Association between caesarean birth and childhood cancer: An age-lagged approach

AIM

We assessed the association between caesarean birth and age-specific risks of childhood cancer.

METHODS

We followed a cohort of 1 034 049 children between 2006 and 2020 in Quebec, Canada, from birth until age 14 years. The exposure was caesarean, operative vaginal, or spontaneous vaginal birth. The outcome included haematopoietic or solid tumours. We calculated hazard ratios (HR) and 95% confidence intervals (CI) for the association between mode of delivery and childhood cancer in age-lagged analyses, adjusted for potential confounders.

RESULTS

A total of 249 415 (24.1%) children were born by caesarean and 97 411 (9.4%) by operative vaginal delivery. Compared with spontaneous vaginal birth, caesarean was associated with 1.16 times the risk of any cancer (95% CI 1.04-1.30), 1.12 times the risk of haematopoietic cancer (95% CI 0.92-1.36) and 1.21 times the risk of solid tumours (95% 1.06-1.39). Associations strengthened at 2 years of age and were greatest for lymphoma and sarcoma. Operative vaginal birth was not significantly associated with the risk of cancer.

CONCLUSION

Caesarean birth may be associated with selected childhood cancers, including lymphoma and sarcoma early in childhood. The underlying reasons for the associations require further investigation, including whether mucosal dysbiosis or labour hormone exposure explain the excess risk.

Cancer Risk in Children of Mothers With Epilepsy and High-Dose Folic Acid Use During Pregnancy

Importance

Women with epilepsy are recommended high doses of folic acid before and during pregnancy owing to risk of congenital anomalies associated with antiseizure medications. Whether prenatal exposure to high-dose folic acid is associated with increases in the risk of childhood cancer is unknown.

Objective

To assess whether high-dose folic acid supplementation in mothers with epilepsy is associated with childhood cancer.

Design, Setting, and Participants

Observational cohort study conducted with nationwide registers in Denmark, Norway, and Sweden from 1997 to 2017. Analyses were performed during January 10, 2022, to January 31, 2022. Mother-child pairs were identified in medical birth registers and linked with information from patient, prescription, and cancer registers, as well as with sociodemographic information from statistical agencies, and were categorized by maternal diagnosis of epilepsy. The study population consisted of 3 379 171 children after exclusion of 126 711 children because of stillbirth or missing or erroneous values on important covariates.

Exposures

Maternal prescription fills for high-dose folic acid tablets (≥1 mg daily) between 90 days before pregnancy start and birth.

Main Outcomes and Measures

First onset of childhood cancer at younger than 20 years. Cox proportional hazards models were used to calculate adjusted hazard ratios with corresponding 95% CIs, adjusted for potential confounders. Cumulative incidence at aged 20 years was used as a measure of absolute risk.

Results

The median age at the end of follow-up in the study population of 3 379 171 children was 7.3 years (IQR, 3.5-10.9 years). Among the 27 784 children (51.4% male) born to mothers with epilepsy, 5934 (21.4%) were exposed to high-dose folic acid (mean dose, 4.3 mg), with 18 exposed cancer cases compared with 29 unexposed, producing an adjusted hazard ratio of 2.7 (95% CI, 1.2-6.3), absolute risk if exposed of 1.4% (95% CI, 0.5%-3.6%), and absolute risk if unexposed of 0.6% (95% CI, 0.3%-1.1%). In children of mothers without epilepsy, 46 646 (1.4%) were exposed to high-dose folic acid (mean dose, 2.9 mg), with 69 exposed and 4927 unexposed cancer cases and an adjusted hazard ratio of 1.1 (95% CI, 0.9-1.4; absolute risk, 0.4% [95% CI, 0.3%-0.5%]). There was no association between children born to mothers with epilepsy who were prenatally exposed to antiseizure medications, but not high-dose folic acid, and an increased risk of cancer (absolute risk, 0.6%; 95% CI, 0.2%-1.3%).

Conclusions and Relevance

Prenatal exposure to high-dose folic acid was associated with increased risk of cancer in children of mothers with epilepsy.

Mapping evidence on the risk factors associated with pediatric cancers in sub-Saharan Africa: a scoping review

BACKGROUND

The rarity and heterogeneity of pediatric cancers make it difficult to assess risk factors associated with the development of cancer in this group. This also determines the quantity and quality of evidence for etiological factors linked to pediatric cancers. Evidence on the risk factors associated with pediatric cancers is scarce; however, it has been accumulating slowly over the years. As the disease burden shifts from communicable to non-communicable diseases, most of these low- to middle-income countries (LMICs) find themselves overburdened with changing health care priorities and needs. In sub-Saharan Africa, it is of major importance to pay particular attention to risk factors associated with pediatric cancer.

OBJECTIVE

To map evidence on risk factors associated with pediatric cancers in sub-Saharan Africa (SSA).

METHODS

This review was guided by Arksey and O'Malley's framework for conducting scoping reviews. Four electronic databases were searched in December 2018, and another manual search was conducted in February 2022 to include newly published eligible articles. The databases searched included PubMed and Health Source: Nursing/Academic Edition. We also searched articles from an academic search engine, Google scholar. This review included articles reporting the relevant outcomes of this study and articles reporting cancers in children in the 0-15 years age range. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews (PRISMA-ScR): checklist and explanation.

RESULTS

We retrieved 7391 articles from the initial database. The final number of studies that were included for data extraction was 15. Evidence from the retrieved studies suggests that most childhood cancers in the SSA region are infection-induced. The type of cancer mostly reported is Burkitt Lymphoma and is diagnosed mostly in the tropical region of SSA. The type of risk factors was divided into three types: infection-induced, genetic, and demographic risk factors. Overall, based on the articles retrieved, there was limited evidence on the risk factors associated with pediatric cancers in SSA.

CONCLUSION

The limited evidence on the risk factors coupled with the lack of evidence on the true burden of these malignancies in the SSA hampers efforts to set priorities for childhood cancer control. Formulation of effective preventative (where possible) measures and treatment regimens will need proper assessment of risk factors.

Increased incidence of childhood lymphoma in children with a history of small for gestational age at birth

OBJECTIVE

The aim of this study was to evaluate whether children that were born small for gestational age (SGA) have an increased risk for childhood neoplasm.

STUDY DESIGN

A population-based cohort analysis comparing the risk for long-term childhood neoplasms (benign and malignant) in children that were born SGA vs. those that were appropriate for gestational age (AGA), between the years1991-2014. Childhood neoplasms were predefined based on ICD-9 codes, as recorded in the hospital medical files. Kaplan-Meier survival curves were constructed to compare cumulative oncological morbidity in both groups over time. Cox proportional hazards model was used to control for confounders.

RESULTS

During the study period 231,973 infants met the inclusion criteria; out of those 10,998 were born with a diagnosis of SGA. Children that were SGA at birth had higher incidence of lymphoma (OR 2.50, 95% CI 1.06-5.82; p value = 0.036). In addition, cumulative incidence over time of total childhood lymphoma was significantly higher in SGA children (Log Rank = 0.030). In a Cox regression model controlling for other perinatal confounders; SGA at birth remained independently associated with an increased risk for childhood lymphoma (adjusted HR 2.41, 95% CI 1.03-5.56, p value = 0.043).

CONCLUSION

Being delivered SGA is associated with an increased long-term risk for childhood malignancy and specifically lymphoma.

Parental age and retinoblastoma-a retrospective study of demographic data and genetic analysis

OBJECTIVE

To determine the association between the parental age gap and the absolute parental age with the risk of retinoblastoma (RB) development in an offspring.

METHODS

RB individuals diagnosed between March 2013 and December 2019 in a single tertiary eye care centre were included. We recorded the demographic data, parental age and RB1 gene mutation status in the patient's tumour, blood and the parental blood. We categorised RB1 mutation inheritance as sporadic RB with somatic mutations (only present in tumour), heritable RB with de novo (present in patient's blood) and familial (present in patient and parents' blood) germline mutations. The statistical significance was confirmed by Fisher's exact/Chi-square test.

RESULTS

Out of 259 RB patients, 247 were included in our study. Heritable RB with de novo germline mutations was significantly less common (p value: 0.0387; 95% CI: 0.2676-0.9329) and sporadic RB with somatic mutations was more common (p value: 0.0545; 95% CI: 1.025-3.39), if the parental age gap was <10 years. There were increased odds of a heritable RB with de novo germline mutation with an increase in paternal age and this was more intensified when combined with parental age gap of more than ≥10 years. The heritable RB with de novo germline mutations significantly increased as maternal age progressed, only when it was adjusted to ≥10 years parental age gap (p value: 0.0262; 95% CI: 1.26-17.91).

CONCLUSIONS

An increased parental age gap and increased paternal age are independent risk factors for the development of heritable RB with de novo germline mutation.

Machine Learning-Based DNA Methylation Score for Fetal Exposure to Maternal Smoking: Development and Validation in Samples Collected from Adolescents and Adults

BACKGROUND

Fetal exposure to maternal smoking during pregnancy is associated with the development of noncommunicable diseases in the offspring. Maternal smoking may induce such long-term effects through persistent changes in the DNA methylome, which therefore hold the potential to be used as a biomarker of this early life exposure. With declining costs for measuring DNA methylation, we aimed to develop a DNA methylation score that can be used on adolescent DNA methylation data and thereby generate a score for in utero cigarette smoke exposure.

METHODS

We used machine learning methods to create a score reflecting exposure to maternal smoking during pregnancy. This score is based on peripheral blood measurements of DNA methylation (Illumina's Infinium HumanMethylation450K BeadChip). The score was developed and tested in the Raine Study with data from 995 white 17-y-old participants using 10-fold cross-validation. The score was further tested and validated in independent data from the Northern Finland Birth Cohort 1986 (NFBC1986) (16-y-olds) and 1966 (NFBC1966) (31-y-olds). Further, three previously proposed DNA methylation scores were applied for comparison. The final score was developed with 204 CpGs using elastic net regression.

RESULTS

Sensitivity and specificity values for the best performing previously developed classifier ("Reese Score") were 88% and 72% for Raine, 87% and 61% for NFBC1986 and 72% and 70% for NFBC1966, respectively; corresponding figures using the elastic net regression approach were 91% and 76% (Raine), 87% and 75% (NFBC1986), and 72% and 78% for NFBC1966.

CONCLUSION

We have developed a DNA methylation score for exposure to maternal smoking during pregnancy, outperforming the three previously developed scores. One possible application of the current score could be for model adjustment purposes or to assess its association with distal health outcomes where part of the effect can be attributed to maternal smoking. Further, it may provide a biomarker for fetal exposure to maternal smoking. https://doi.org/10.1289/EHP6076.

Maternal and paternal ages at conception of index child and risk of childhood acute leukaemia: A multicentre case-control study in Greater Mexico City

BACKGROUND

The parental age at conception has been reported to be a risk factor for childhood acute leukaemia (AL); however, the relationship is controversial. The aim of the present study was to investigate the association between parental age at conception and the risk of AL in Mexican children, a population with a high incidence of the disease and a high prevalence of pregnancies in adolescents and young adults.

METHODS

A multicentre case-control study was conducted. Incident AL cases younger than 17 years of age diagnosed between 2010 and 2015 were included. Controls were matched with cases according to age, sex, and health institution. Using logistic regression analysis, adjusted odds ratios (aOR) and 95 % confidence intervals (95 % CI) were calculated for each maternal stratum after adjusting for paternal age at conception of index child. The maternal age between 25 and 29.99 years was selected as the reference category.

RESULTS

In most strata where maternal and paternal ages were assessed, no association was found with the risk of developing acute lymphoblastic leukaemia (ALL) and acute myeloid leukaemia (AML) in their offspring. An increased risk for AML was observed when the mother was between 20 and 24.99 years of age and the father aged 25-29.99 years (aOR, 1.94; 95 % CI, 1.03-3.67). In addition, there was a positive association for ALL when the mother´s age was between 20 and 24.99 years and the father was <20 years of age, however, a very wide confidence interval was noted (aOR, 12.26; 95 % CI, 1.41-106.83).

CONCLUSION

In the present study, maternal and paternal ages assessed in different strata showed little association with risk of developing ALL and AML in children. Positive associations between risk of both types of childhood AL were observed with younger paternal and maternal ages.

Maternal Smoking During Pregnancy Induces Persistent Epigenetic Changes Into Adolescence, Independent of Postnatal Smoke Exposure and Is Associated With Cardiometabolic Risk

Background: Several studies have shown effects of current and maternal smoking during pregnancy on DNA methylation of CpG sites in newborns and later in life. Here, we hypothesized that there are long-term and persistent epigenetic effects following maternal smoking during pregnancy on adolescent offspring DNA methylation, independent of paternal and postnatal smoke exposure. Furthermore, we explored the association between DNA methylation and cardiometabolic risk factors at 17 years of age. Materials and Methods: DNA methylation was measured using the Illumina HumanMethylation450K BeadChip in whole blood from 995 participants attending the 17-year follow-up of the Raine Study. Linear mixed effects models were used to identify differential methylated CpGs, adjusting for parental smoking during pregnancy, and paternal, passive, and adolescent smoke exposure. Additional models examined the association between DNA methylation and paternal, adolescent, and passive smoking over the life course. Offspring CpGs identified were analyzed against cardiometabolic risk factors (blood pressure, triacylglycerols (TG), high-density lipoproteins cholesterol (HDL-C), and body mass index). Results: We identified 23 CpGs (genome-wide p level: 1.06 × 10-7) that were associated with maternal smoking during pregnancy, including associated genes AHRR (cancer development), FTO (obesity), CNTNAP2 (developmental processes), CYP1A1 (detoxification), MYO1G (cell signalling), and FRMD4A (nicotine dependence). A sensitivity analysis showed a dose-dependent relationship between maternal smoking and offspring methylation. These results changed little following adjustment for paternal, passive, or offspring smoking, and there were no CpGs identified that associated with these variables. Two of the 23 identified CpGs [cg00253568 (FTO) and cg00213123 (CYP1A1)] were associated with either TG (male and female), diastolic blood pressure (female only), or HDL-C (male only), after Bonferroni correction. Discussion: This study demonstrates a critical timing of cigarette smoke exposure over the life course for establishing persistent changes in DNA methylation into adolescence in a dose-dependent manner. There were significant associations between offspring CpG methylation and adolescent cardiovascular risk factors, namely, TG, HDL-C, and diastolic blood pressure. Future studies on current smoking habits and DNA methylation should consider the importance of maternal smoking during pregnancy and explore how the persistent DNA methylation effects of in utero smoke exposure increase cardiometabolic risk.

Pregnancy-associated cancers and birth outcomes in children: a Danish and Swedish population-based register study

OBJECTIVES

This study aims to estimate the association between pregnancy-associated maternal cancers, diagnosed both prenatally and postnatally, and birth outcomes.

DESIGN

Population-based register study.

SETTING

National registers of Denmark and Sweden.

PARTICIPANTS

A total of 5 523 365 children born in Denmark (1977-2008) and Sweden (1973-2006).Primary and secondary outcome measures: gestational age, birth weight, size for gestational age, Apgar score, caesarean section and sex were the outcomes of interest. ORs and relative risk ratios (RRR) with 95% CIs were estimated using logistic regression and multinomial logistic regression, respectively.

RESULTS

In this study, 2% of children were born to mothers with a diagnosis of cancer. Children whose mothers received a prenatal cancer diagnosis had higher risk of being born preterm (RRR: 1.77, 95% CI 1.64 to 1.90); low birth weight (RRR 1.84, 95% CI 1.69 to 2.01); low Apgar score (OR 1.36, 95% CI 1.20 to 1.56); and by caesarean section (OR: 1.69, 95% CI 1.59 to 1.80). Associations moved towards the null for analyses using postnatal diagnoses, but preterm birth (RRR: 1.13, 95% CI 1.09 to 1.17) and low birth weight (RRR: 1.14, 95% CI 1.09 to 1.18) remained statistically significant, while risk of caesarean section became so (OR: 0.95, 95% CI 0.91 to 0.98). Additionally, statistical significance was reached for large for gestational age (RRR: 1.06, 95% CI 1.01 to 1.11), high birth weight (RRR: 1.04, 95% CI 1.01 to 1.06) and caesarean section (OR: 0.95, 95% CI 0.91 to 0.98).

CONCLUSIONS

Results suggest an association between pregnancy-associated cancers and adverse birth outcomes in the offspring. While this is strongest for prenatally diagnosed cancers, some smaller associations exist for postnatally diagnosed cancers, indicating that cancer itself could affect fetal development, or that cancer and adverse birth outcomes share risk factors. Future studies on maternal cancer during pregnancy should consider including some postnatal years in their exposure window.

Reproductive Outcomes After a Childhood and Adolescent Young Adult Cancer Diagnosis in Female Cancer Survivors: A Systematic Review and Meta-analysis

Improvements in cancer therapy for childhood and adolescent and young adult (AYA) survivors have increased in excess of 80% among pediatric patients and in excess of 85% among AYA cancer patients. Our research group explored the late effects consequences of cancer treatment on pregnancy and birth outcomes subsequent to a childhood (0-14 years) or AYA (15-25 years) diagnosis of cancer in female cancer survivors. Embase and Medline databases were searched. There were 17 review (n = 10 matched and n = 7 unmatched) studies that met the inclusion criteria. Subanalyses were conducted on 10 matched studies. The median age for all studies for patients at diagnosis and birth was 11 and 27 years, respectively. In matched cohort studies, female childhood and AYA cancer patients, who received chemotherapy alone, had a pooled estimated rate of 18% of experiencing a live birth compared with 10% of females who received radiotherapy alone and subsequently had a live birth. Females who received surgery alone reported higher pooled estimated rates of 44% for a live birth. For matched retrospective review studies, 79% (n = 973) of women experienced a live birth, of which 22% of these babies were born preterm. This meta-analysis found lower birth rates for survivors. Access to fertility-related information and discussions around fertility preservation options and oncofertility psychosocial support should be offered to all cancer patients and their families before starting cancer treatment.

Maternal Immunization: New Perspectives on Its Application Against Non-Infectious Related Diseases in Newborns

The continuous evolution in preventive medicine has anointed vaccination a versatile, human-health improving tool, which has led to a steady decline in deaths in the developing world. Maternal immunization represents an incisive step forward for the field of vaccination as it provides protection against various life-threatening diseases in pregnant women and their children. A number of studies to improve prevention rates and expand protection against the largest possible number of infections are still in progress. The complex unicity of the mother-infant interaction, both during and after pregnancy and which involves immune system cells and molecules, is an able partner in the success of maternal immunization, as intended thus far. Interestingly, new studies have shed light on the versatility of maternal immunization in protecting infants from non-infectious related diseases, such as allergy, asthma and congenital metabolic disorders. However, barely any attempt at applying maternal immunization to the prevention of childhood cancer has been made. The most promising study reported in this new field is a recent proof of concept on the efficacy of maternal immunization in protecting cancer-prone offspring against mammary tumor progression. New investigations into the possibility of exploiting maternal immunization to prevent the onset and/or progression of neuroblastoma, one of the most common childhood malignancies, are therefore justified. Maternal immunization is presented in a new guise in this review. Attention will be focused on its versatility and potential applications in preventing tumor progression in neuroblastoma-prone offspring.

Parental age and childhood cancer risk: A Danish population-based registry study

BACKGROUND

Though the association between parental age at child's birth and the risk of childhood cancer has been previously investigated, the evidence to date is inconclusive and scarce for rarer cancer types.

METHODS

Cancer cases (N=5,856) were selected from all children born from 1968 to 2014 and diagnosed from 1968 to 2015 in Denmark at less than 16 years of age listed in the nationwide Danish Cancer Registry. Cases were individually matched to controls (1:100) on sex and year of birth with a total of 585,594 controls randomly sampled from all live births in Denmark from the Danish Central Population Registry. Parental age at child's birth was extracted from the Central Population Registry. Conditional logistic regression models were used to estimate odds ratios for the association between parental age at child's birth and childhood cancer risk. Parental age was modeled as both categorical (referent group, parents aged 25-29) and continuous per 5-year increase in age.

RESULTS

Offspring of older mothers were at an increased risk of acute lymphoblastic leukemia [OR=1.10, 95% CI: (1.02, 1.19) per 5-year increase in age]. Older maternal age (40+) increased the risk of non-Hodgkin lymphoma [OR=1.96, 95%CI: (1.12, 3.43)]. The risk of Wilms' tumor also appeared elevated with older paternal age [OR=1.11, 95% CI: (0.97, 1.28) per 5-year increment in age].

CONCLUSION

Older parental age was a risk factor for various childhood cancers in Danish children. Further investigation of the biological and social factors that may be contributing to these associations is warranted.

Prenatal exposure to tobacco smoke leads to increased mitochondrial DNA content in umbilical cord serum associated to reduced gestational age

We investigated if prenatal exposures to tobacco smoke lead to changes in mitochondrial DNA content (mtDNA) in cord serum and adversely affect newborns' health. Umbilical cord serum cotinine levels were used to determine in utero exposure to smoking. Cord serum mtDNA was measured by quantitative polymerase chain reaction analysis of the genes coding for cytochrome c oxidase1 (MT-CO1) and cytochrome c oxidase2 (MT-CO2). Log transformed levels of mtDNA coding for MT-CO1 and MT-CO2 were significantly higher among infants of active smokers with higher serum level of cotinine (p < 0.05) and inversely associated with gestational age (p = 0.08; p = 0.02). Structural equation modeling results confirmed a positive association between cotinine and MT-CO1 and2 (p < 0.01) and inverse associations with gestational age (p = 0.02) and IGF-1 (p < 0.01). We identified a dose-dependent increase in the level of MT-CO1 and MT-CO2 associated to increased cord serum cotinine and decreased gestational age.

Maternal smoking impacts key biological pathways in newborns through epigenetic modification in Utero

BACKGROUND

Children exposed to maternal smoking during pregnancy exhibit increased risk for many adverse health effects. Maternal smoking influences methylation in newborns at specific CpG sites (CpGs). Here, we extend evaluation of individual CpGs to gene-level and pathway-level analyses among 1062 participants in the Norwegian Mother and Child Cohort Study (MoBa) using the Illumina 450 K platform to measure methylation in newborn DNA and maternal smoking in pregnancy, assessed using the biomarker, plasma cotinine. We used novel implementations of bioinformatics tools to collapse epigenome-wide methylation data into gene- and pathway-level effects to test whether exposure to maternal smoking in utero differentially methylated CpGs in genes enriched in biologic pathways. Unlike most pathway analysis applications, our approach allows replication in an independent cohort.

RESULTS

Data on 485,577 CpGs, mapping to a total of 20,199 genes, were used to create gene scores that were tested for association with maternal plasma cotinine levels using Sequence Kernel Association Test (SKAT), and 15 genes were found to be associated (q < 0.25). Six of these 15 genes (GFI1, MYO1G, CYP1A1, RUNX1, LCTL, and AHRR) contained individual CpGs that were differentially methylated with regards to cotinine levels (p < 1.06 × 10-7). Nine of the 15 genes (FCRLA, MIR641, SLC25A24, TRAK1, C1orf180, ITLN2, GLIS1, LRFN1, and MIR451) were associated with cotinine at the gene-level (q < 0.25) but had no genome-wide significant individual CpGs (p > 1.06 × 10-7). Pathway analyses using gene scores resulted in 51 significantly associated pathways, which we tested for replication in an independent cohort (q < 0.05). Of those 32 replicated in an independent cohort, which clustered into six groups. The largest cluster consisted of pathways related to cancer, cell cycle, ERα receptor signaling, and angiogenesis. The second cluster, organized into five smaller pathway groups, related to immune system function, such as T-cell regulation and other white blood cell related pathways.

CONCLUSIONS

Here we use novel implementations of bioinformatics tools to determine biological pathways impacted through epigenetic changes in utero by maternal smoking in 1062 participants in the MoBa, and successfully replicate these findings in an independent cohort. The results provide new insight into biological mechanisms that may contribute to adverse health effects from exposure to tobacco smoke in utero.

Is yolk sac tumor related to the pathophysiology of low birthweight?

An 8-year-old Japanese girl was admitted with an ovarian yolk sac tumor. Regarding birth history, the patient had been delivered by cesarean section at 25 weeks of gestation with a birthweight of 711g. She had required neonatal intensive care including oxygenation, various medications, and tests. After surgery and chemotherapy, there was no recurrence for 2 years, at the time of writing. Yolk sac tumor, which is a malignant germ cell tumor, is rare in children. Although the cause and risk factors are unclear, it has been reported that malignant germ cell tumors in childhood have been associated with pathophysiology at birth. Given that premature infants are more likely to survive due to advances in perinatal care, it is expected that such cases will increase in the near future. We suggest that children born prematurely require careful follow up.

Cancer risks for relatives of children with cancer

We determined the extent and distribution of cancers in relatives of 379 children newly diagnosed with cancer. Family history was collected from 1,337 first-degree and 3,399 second-degree relatives and incidence compared with national age- and gender-specific rates. Overall, 14 children (3.7%) had a relative with a history of childhood cancer and 26 children (6.9%) had a first-degree relative with a history of cancer, with only one of these having an identifiable familial cancer syndrome. There was a higher than expected incidence of childhood cancer among first-degree relatives (parents and siblings) (standardized incidence ratio (SIR) 1.43; 95% CI 0.54–5.08). There was also a higher than expected incidence of adult cancers among first-degree relatives (SIR 1.45; 95% CI 0.93–2.21), particularly in females (SIR 1.82; 95% CI 1.26–3.39). The increased family cancer history in first-degree females was largely attributable to an effect in mothers (SIR 1.78; 95% CI 1.27–3.33). The gender-specific association was reflected in higher than expected incidence rates of breast cancer in both mothers (SIR 1.92; 95% CI 0.72–6.83) and aunts (SIR 1.64; 95% CI 0.98–2.94). These findings support the hypothesis that previously undetected familial cancer syndromes contribute to childhood cancer.