Childhood hematopoietic malignancies and parental use of tobacco and alcohol: the ESCALE study (SFCE)

Maternal Prenatal Use of Alcohol, Tobacco, and Illicit Drugs and Associations with Childhood Cancer Subtypes

BACKGROUND

The association between childhood cancer risk and maternal prenatal substance use/abuse remains uncertain due to modest sample sizes and heterogeneous study designs.

METHODS

We surveyed parents of children with cancer regarding maternal gestational use of tobacco, alcohol, and illicit drugs, using a Likert-type scale, and demographic, perinatal, and clinical variables. Multivariable log-Poisson regression assessed differences in frequency of prenatal substance use across fifteen childhood cancer subtypes, adjusting for birthweight, gestational age, and demographic factors.

RESULTS

Respondents from 3,145 unique families completed the survey (92% biological mothers). A minority reported gestational use of tobacco products (14%), illicit drugs including marijuana or cocaine (4%), or more than a moderate amount of alcohol (2%). Prenatal illicit drug use was associated with increased prevalence of intracranial embryonal tumors [prevalence ratio (PR) = 1.94; confidence interval [CI], 1.05-3.58], including medulloblastoma (PR = 1.82) and supratentorial primitive neuroectodermal tumors (PNET; PR = 2.66), and was also associated with retinoblastoma (PR = 3.11; CI, 1.20-8.08). Moderate to heavy alcohol consumption was strongly associated with elevated prevalence of non-Hodgkin lymphoma (PR = 5.94; CI, 1.84-19.21). Prenatal smoking was not associated with elevated prevalence of any childhood cancer subtype.

CONCLUSIONS

We identify novel associations between illicit drug use during pregnancy and increased prevalence of nonglioma central nervous system tumors, including medulloblastoma, supratentorial PNETs, and retinoblastoma. Gestational exposure to alcohol was positively associated with non-Hodgkin lymphoma.

IMPACT

Although alcohol and tobacco use during pregnancy has declined, gestational cannabis use has risen. Investigating its impact on neurodevelopment and brain tumorigenesis is vital, with important implications for childhood cancer research and public health education.

Environmental, social and behavioral risk factors in association with spatial clustering of childhood cancer incidence

Childhood cancer incidence is known to vary by age, sex, and race/ethnicity, but evidence is limited regarding external risk factors. We aim to identify harmful combinations of air pollutants and other environmental and social risk factors in association with the incidence of childhood cancer based on 2003-2017 data from the Georgia Cancer Registry. We calculated the standardized incidence ratios (SIR) of Central Nervous System (CNS) tumors, leukemia and lymphomas based on age, gender and ethnic composition in each of the 159 counties in Georgia, USA. County-level information on air pollution, socioeconomic status (SES), tobacco smoking, alcohol drinking and obesity were derived from US EPA and other public data sources. We applied two unsupervised learning tools (self-organizing map [SOM] and exposure-continuum mapping [ECM]) to identify pertinent types of multi-exposure combinations. Spatial Bayesian Poisson models (Leroux-CAR) were fit with indicators for each multi-exposure category as exposure and SIR of childhood cancers as outcomes. We identified consistent associations of environmental (pesticide exposure) and social/behavioral stressors (low socioeconomic status, alcohol) with spatial clustering of pediatric cancer class II (lymphomas and reticuloendothelial neoplasms), but not for other cancer classes. More research is needed to identify the causal risk factors for these associations.

Genotype-Environment Interaction Analysis of NQO1, CYP2E1, and NAT2 Polymorphisms and the Risk of Childhood Acute Lymphoblastic Leukemia: A Report From the Mexican Interinstitutional Group for the Identification of the Causes of Childhood Leukemia

Background: Acute lymphoblastic leukemia (ALL) is the main type of cancer in children. In Mexico and other Hispanic populations, the incidence of this neoplasm is one of the highest reported worldwide. Functional polymorphisms of various enzymes involved in the metabolism of xenobiotics have been associated with an increased risk of developing ALL, and the risk is different by ethnicity. The aims of the present study were to identify whether NQO1, CYP2E1, and NAT2 polymorphisms or some genotype-environmental interactions were associated with ALL risk in Mexican children.

Methods: We conducted a case-control study including 478 pediatric patients diagnosed with ALL and 284 controls (children without leukemia). Ancestry composition of a subset of cases and controls was assessed using 32 ancestry informative markers. Genetic-environmental interactions for the exposure to hydrocarbons were assessed by logistic regression analysis.

Results: The polymorphisms rs1801280 (OR 1.54, 95% CI 1.21–1.93), rs1799929 (OR 1.96, 95% CI 1.55–2.49), and rs1208 (OR 1.44, 95% CI 1.14–1.81) were found to increase the risk of ALL; being the risks higher under a recessive model (OR 2.20, 95% CI 1.30–1.71, OR 3.87, 95% CI 2.20–6.80, and OR 2.26, 95% CI 1.32–3.87, respectively). Gene-environment interaction analysis showed that NAT2 rs1799929 TT genotype confers high risk to ALL under exposure to fertilizers, insecticides, hydrocarbon derivatives, and parental tobacco smoking. No associations among NQO1, CYP2E1, and ALL were observed.

Conclusion: Our study provides evidence for the association between NAT2 polymorphisms/gene-environment interactions, and the risk of childhood ALL in Mexican children.

Parental tobacco smoking and risk of childhood leukemia in Costa Rica: A population-based case-control study

INTRODUCTION

The role of environmental and behavioral exposures on childhood leukemia etiology is poorly understood. We examined the association of maternal and paternal tobacco smoking at different time points with the risk of acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) in Costa Rican children.

MATERIALS AND METHODS

We conducted a population-based case-control study on childhood leukemia in Costa Rica. Cases (n ALL = 252; n AML = 40) were diagnosed between 1995 and 2000 (aged <15 years at diagnosis) and identified from the Costa Rican Cancer Registry and the National Children's Hospital. A total of 578 frequency-matched population controls were sampled from the National Birth Registry. Parental tobacco smoking was assessed via face-to-face interviews. We used logistic regression models to examine the association of paternal and maternal tobacco smoking before conception, during pregnancy, and after birth with childhood ALL and AML risk, adjusted for child sex, birth year, maternal/paternal age, and parental education.

RESULTS

Paternal smoking before conception, during pregnancy, and after birth was associated with an increased risk of childhood AML (Odds Ratio (OR): 2.51, 95% CI: 1.21-5.17; OR: 3.21, 95% CI: 1.56-6.60; and OR: 2.83, 95% CI: 1.36-5.90, respectively). Maternal smoking during pregnancy was also associated with a modest, but imprecise increase in AML risk. We observed null associations of maternal and paternal smoking with ALL in the offspring.

CONCLUSION

Our results suggest an association between parental smoking and risk of AML, but not ALL, in Costa Rican children. These findings add to the established evidence of numerous health risks associated with smoking and highlight the potential harm of smoking during sensitive windows of the development of fetus and child.

Paternal Smoking Before Conception and During Pregnancy Is Associated With an Increased Risk of Childhood Acute Lymphoblastic Leukemia: A Systematic Review and Meta-Analysis of 17 Case-Control Studies

OBJECTIVE

Current evidence regarding the association between paternal smoking before conception or during pregnancy and the risk of childhood acute lymphoblastic leukemia (ALL) are inconsistent. We aimed to systematically summarize the current evidence regarding this potential association.

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and the Meta-analysis of Observational Studies in Epidemiology (MOOSE), we systematically retrieved PubMed, Embase, Web of Science, and Scopus, screened relevant literature, and assessed the methodologic quality of the included studies. We calculated the pooled estimates using random-effects models. We assessed statistical heterogeneity by I values and χ tests for the Cochrane Q statistic. We further investigate the dose-response relation using 2-stage nonlinear models.

RESULTS

A total of 17 case-control studies were identified, and the synthesized risk ratios (RRs) for smoking before conception (RR=1.15, 95% confidence interval: 1.04-1.27) and during pregnancy (RR=1.20, 95% confidence interval: 1.12-1.28) were both statistically significant. Moreover, the dose-response analysis showed a positive association as well.

CONCLUSION

Current evidence from observational studies suggests the association between paternal smoking before conception or during pregnancy and the increased risk of childhood ALL, which needs to be confirmed in prospective studies.

Tobacco smoke exposure and the risk of childhood acute lymphoblastic leukemia and acute myeloid leukemia: A meta-analysis

OBJECTIVE

Tobacco smoke contains carcinogens known to damage somatic and germ cells. In this study, we investigated the effect of tobacco smoking on the risk of childhood acute lymphoblastic leukemia (ALL) and myeloid leukemia (AML).

METHODS

Information about tobacco smoking exposures of the mother before, during, and after pregnancy was collected via PubMed, Embase, and Web of Science databases through November 5, 2018. We performed to evaluate the association between smoking exposure and the risk of childhood ALL and AML. Study selection, data abstraction, and quality assessment were performed by 2 independent reviewers. Random effects models were used to obtain summary odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Nineteen case-control studies of childhood leukemia (age < 15 years) conducted in 9 countries from 1974 to 2018. Maternal smoking exposures did not a significant association with childhood ALL (OR = 1.004, 95% CI 0.953-1.058, P = .881) and AML (OR = 0.92, 95% CI 0.815-1.038, P = .177) during exposure time windows. However, there was an association with paternal smoking and ALL (OR = 1.15, 95% CI 1.038-1.275, P = .007). Paternal smoking in AML showed there was no association with smoking exposures and childhood AML (OR = 1.133, 95% CI 0.943-1.362, P = .181). Next, maternal daily cigarettes consumption showed no associations with ALL (OR = 1.08, 95% CI 1.000-1.168, P = .051) during pregnancy. No association with maternal daily smoking and AML (OR = 0.909, 95% CI 0.682-1.211, P = .514). Paternal daily cigarettes consumption was associated with increased risks of childhood ALL (OR = 1.200, 95% CI 1.112-1.302, P = .000). The higher consumption of paternal smoking (more than 10 per day) was significantly related to childhood ALL. Paternal daily smoking consumption also was related to AML (OR = 1.242, 95% CI 1.031-1.496, P = .022).

CONCLUSION

Maternal smoking before, during, or after pregnancy was not associated with childhood ALL or AML. However, paternal smoking was related to a significantly elevated risk of childhood ALL during pregnancy, but not for AML. Maternal daily smoking consumption was not associated with ALL or AML during pregnancy. The higher consumption of paternal smoking were, the higher the risk of childhood ALL or AML.

Is There Etiologic Heterogeneity between Subtypes of Childhood Acute Lymphoblastic Leukemia? A Review of Variation in Risk by Subtype

Although substantial advances in the identification of cytogenomic subtypes of childhood acute lymphoblastic leukemia (ALL) have been made in recent decades, epidemiologic research characterizing the etiologic heterogeneity of ALL by subtype has not kept pace. The purpose of this review is to summarize the current literature concerning subtype-specific epidemiologic risk factor associations with ALL subtype defined by immunophenotype (e.g., B-cell vs. T-cell) and cytogenomics (including gross chromosomal events characterized by recurring numerical and structural abnormalities, along with cryptic balanced rearrangements, and focal gene deletions). In case-control analyses investigating nongenetic risk factors, home paint exposure is associated with hyperdiploid, MLL-rearranged, and ETV6-RUNX1 subtypes, yet there are few differences in risk factor associations between T- and B-ALL. Although the association between maternal smoking and ALL overall has been null, maternal smoking is associated with an increasing number of gene deletions among cases. GWAS-identified variants in ARID5B have been the most extensively studied and are strongly associated with hyperdiploid B-ALL. GATA3 single nucleotide variant rs3824662 shows a strong association with Ph-like ALL (OR = 3.14). However, there have been relatively few population-based studies of adequate sample size to uncover risk factors that may define etiologic heterogeneity between and within the currently defined cytogenomic ALL subtypes.

Maternal prenatal exposure to environmental factors and risk of childhood acute lymphocytic leukemia: A hospital-based case-control study in China

OBJECTIVE

To investigate an association between maternal prenatal exposure to several environmental factors and risk of childhood acute lymphocytic leukemia (ALL), and the possible interactions in the Chinese population.

METHODS

345 cases with ALL and their 1:1 age, gender, residence region matched controls aged 0-15 years were recruited from four hospitals in Henan Province from 2014 to 2016. Information was collected by interviews using a questionnaire. Unconditional logistic regression adjusted for age, gender, residence region and relevant confounders was carried out to generate the odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Our data indicate that maternal prenatal exposure to interior housing renovation (adjusted OR: 2.98, 95% CI: 1.51-5.86) or pesticides (adjusted OR: 1.48, 95% CI: 1.67-2.28) increased the risk of childhood ALL. Various subgroup analyses stratified by child's gender, age at diagnosis and other factors also supported these results. However, no interaction was detected between exposure to internal housing renovation and pesticides using an additive model. No significant links between maternal exposures to, environmental tobacco smoking (ETS), antipyretic analgesia intake, or viral infectious diseases with risk of ALL were detected.

CONCLUSION

Findings in our study are in line with the existing literatures, which support the hypothesis that maternal prenatal exposure to interior housing renovation and pesticides are risk factors for childhood ALL. Notably, we found no interaction between these two risk factors, these findings may inform prevention and early detection strategies.

The effect of paternal factors on perinatal and paediatric outcomes: a systematic review and meta-analysis

BACKGROUND

Maternal factors, including increasing childbearing age and various life-style factors, are associated with poorer short- and long-term outcomes for children, whereas knowledge of paternal parameters is limited. Recently, increasing paternal age has been associated with adverse obstetric outcomes, birth defects, autism spectrum disorders and schizophrenia in children.

OBJECTIVE AND RATIONALE

The aim of this systematic review is to describe the influence of paternal factors on adverse short- and long-term child outcomes.

SEARCH METHODS

PubMed, Embase and Cochrane databases up to January 2017 were searched. Paternal factors examined included paternal age and life-style factors such as body mass index (BMI), adiposity and cigarette smoking. The outcome variables assessed were short-term outcomes such as preterm birth, low birth weight, small for gestational age (SGA), stillbirth, birth defects and chromosomal anomalies. Long-term outcome variables included mortality, cancers, psychiatric diseases/disorders and metabolic diseases. The systematic review follows PRISMA guidelines. Relevant meta-analyses were performed.

OUTCOMES

The search included 14 371 articles out of which 238 met the inclusion criteria, and 81 were included in quantitative synthesis (meta-analyses). Paternal age and paternal life-style factors have an association with adverse outcome in offspring. This is particularly evident for psychiatric disorders such as autism, autism spectrum disorders and schizophrenia, but an association is also found with stillbirth, any birth defects, orofacial clefts and trisomy 21. Paternal height, but not BMI, is associated with birth weight in offspring while paternal BMI is associated with BMI, weight and/or body fat in childhood. Paternal smoking is found to be associated with an increase in SGA, birth defects such as congenital heart defects, and orofacial clefts, cancers, brain tumours and acute lymphoblastic leukaemia. These associations are significant although moderate in size, with most pooled estimates between 1.05 and 1.5, and none exceeding 2.0.

WIDER IMPLICATIONS

Although the increased risks of adverse outcome in offspring associated with paternal factors and identified in this report represent serious health effects, the magnitude of these effects seems modest.

Early Life Exposures and Adult Cancer Risk

Very little is known about the influence of early life exposures on adult cancer risk. The purpose of this narrative review was to summarize the epidemiologic evidence relating early life tobacco use, obesity, diet, and physical activity to adult cancer risk; describe relevant theoretical frameworks and methodological strategies for studying early life exposures; and discuss policies and research initiatives focused on early life. Our findings suggest that in utero exposures may indirectly influence cancer risk by modifying biological pathways associated with carcinogenesis; however, more research is needed to firmly establish these associations. Initiation of exposures during childhood and adolescence may impact cancer risk by increasing duration and lifetime exposure to carcinogens and/or by acting during critical developmental periods. To expand the evidence base, we encourage the use of life course frameworks, causal inference methods such as Mendelian randomization, and statistical approaches such as group-based trajectory modeling in future studies. Further, we emphasize the need for objective exposure biomarkers and valid surrogate endpoints to reduce misclassification. With the exception of tobacco use, there is insufficient evidence to support the development of new cancer prevention policies; however, we highlight existing policies that may reduce the burden of these modifiable risk factors in early life.

Cross-generational effects of alcohol dependence in humans on HRAS and TP53 methylation in offspring

AIM

We hypothesized that cross-generational effects of alcohol exposure could alter DNA methylation and expression of the HRAS oncogene and TP53 tumor suppressor gene that drive cancer development.

METHODS

DNA methylation of the HRAS and TP53 genes was tested in samples from young participants (Mean age of 13.4 years).

RESULTS

Controlling for both personal use and maternal use of substances during pregnancy, familial alcohol dependence was associated with hypomethylation of CpG sites in the HRAS promoter region and hypermethylation of the TP53 gene.

CONCLUSION

The results suggest that ancestral exposure to alcohol can have enduring effects that impact epigenetic processes such as DNA methylation that controls expression of genes that drive cancer development such as HRAS and TP53.

From sperm to offspring: Assessing the heritable genetic consequences of paternal smoking and potential public health impacts

Individuals who smoke generally do so with the knowledge of potential consequences to their own health. What is rarely considered are the effects of smoking on their future children. The objective of this work was to review the scientific literature on the effects of paternal smoking on sperm and assess the consequences to offspring. A literature search identified over 200 studies with relevant data in humans and animal models. The available data were reviewed to assess the weight of evidence that tobacco smoke is a human germ cell mutagen and estimate effect sizes. These results were used to model the potential increase in genetic disease burden in offspring caused by paternal smoking, with specific focus on aneuploid syndromes and intellectual disability, and the socioeconomic impacts of such an effect. The review revealed strong evidence that tobacco smoking is associated with impaired male fertility, and increases in DNA damage, aneuploidies, and mutations in sperm. Studies support that these effects are heritable and adversely impact the offspring. Our model estimates that, with even a modest 25% increase in sperm mutation frequency caused by smoke-exposure, for each generation across the global population there will be millions of smoking-induced de novo mutations transmitted from fathers to offspring. Furthermore, paternal smoking is estimated to contribute to 1.3 million extra cases of aneuploid pregnancies per generation. Thus, the available evidence makes a compelling case that tobacco smoke is a human germ cell mutagen with serious public health and socio-economic implications. Increased public education should be encouraged to promote abstinence from smoking, well in advance of reproduction, to minimize the transmission of harmful mutations to the next-generation.

Maternal Smoking and the Risk of Cancer in Early Life - A Meta-Analysis

BACKGROUND

In spite of the well-known harmful effects on the fetus, many women continue smoking during pregnancy. Smoking as an important source of toxic chemicals may contribute to the developmental origin of diseases.

OBJECTIVES

The aim of this work was to pursue the possible association between maternal smoking and cancer in early life. Specifically, we wanted to identify the associated early life cancer types, and to quantify the associations.

METHODS

In a systematic literature search 825 articles were identified in PubMed and Web of Science, and 55 more through the reference lists. Of these 62 fulfilled the criteria for inclusion in meta-analyses. Using Mantel-Haenszel or DerSimonian and Laird method, depending on heterogeneity of the studies, pooled estimates and 95% confidence intervals for eight cancer types were calculated.

RESULTS

Smoking during pregnancy was associated with an increased risk for for brain and central nervous system tumors (OR = 1.09; 95% CI = 1.02-1.17). Although the risk for lymphoma was also associated (OR = 1.21; 95% CI = 1.05-1.34), it did not hold up in subgroup analyses. Leukemia was not found to be associated with maternal smoking. Five other cancer types (bone, soft tissue, renal, hepatic, and germ cell cancer) were also examined, but the number of studies was too limited to exclude the possibility of maternal smoking as a risk factor for cancer in offspring.

CONCLUSIONS

According to our meta-analyses, maternal smoking is associated with nervous system cancers, but not with leukemia in early life. Confirming or rejecting associations of maternal smoking with lymphoma and the five other cancer types requires further studies.

Parental Tobacco Smoking and Acute Myeloid Leukemia: The Childhood Leukemia International Consortium

The association between tobacco smoke and acute myeloid leukemia (AML) is well established in adults but not in children. Individual-level data on parental cigarette smoking were obtained from 12 case-control studies from the Childhood Leukemia International Consortium (CLIC, 1974-2012), including 1,330 AML cases diagnosed at age <15 years and 13,169 controls. We conducted pooled analyses of CLIC studies, as well as meta-analyses of CLIC and non-CLIC studies. Overall, maternal smoking before, during, or after pregnancy was not associated with childhood AML; there was a suggestion, however, that smoking during pregnancy was associated with an increased risk in Hispanics (odds ratio = 2.08, 95% confidence interval (CI): 1.20, 3.61) but not in other ethnic groups. By contrast, the odds ratios for paternal lifetime smoking were 1.34 (95% CI: 1.11, 1.62) and 1.18 (95% CI: 0.92, 1.51) in pooled and meta-analyses, respectively. Overall, increased risks from 1.2- to 1.3-fold were observed for pre- and postnatal smoking (P < 0.05), with higher risks reported for heavy smokers. Associations with paternal smoking varied by histological type. Our analyses suggest an association between paternal smoking and childhood AML. The association with maternal smoking appears limited to Hispanic children, raising questions about ethnic differences in tobacco-related exposures and biological mechanisms, as well as study-specific biases.

Smoking in pregnancy and risk of cancer among young children: A population-based study

Smoking during pregnancy is a plausible risk factor for childhood cancer, yet previous studies have yielded conflicting results, and few prospective studies have been published. Data on maternal smoking were obtained from California birth certificates. We linked California birth certificates (births 2007-2011) with California Cancer Registry records for childhood cancer cases (diagnosed January 2007-September 2013) that were ages 5 or younger at diagnosis (N cases = 2,021). Controls (N = 40,356) were frequency-matched by birth year and randomly selected from birth certificate records. We used unconditional logistic regression to obtain odds ratios (OR) and 95% confidence intervals (CI) to assess the association between smoking during pregnancy and childhood cancer. We observed positive associations for gliomas (OR = 1.8, 95% CI: 1.0-3.4) and retinoblastoma (OR = 3.0, 95% CI: 1.4-6.6), particularly bilateral retinoblastoma (OR = 9.4, 95% CI 3.6-24.7) with maternal smoking in pregnancy. Maternal smoking during pregnancy may be a risk factor for retinoblastoma and certain types of childhood brain tumors.

Breastfeeding, Other Early Life Exposures and Childhood Leukemia and Lymphoma

Childhood cancer incidence increases and although rare, it is a leading cause of mortality. Leukemia and lymphoma comprise 40% of all cancers in children but little is known of their etiology. In this study, we examined the associations of breastfeeding and other early life exposures with childhood leukemia and lymphoma. A population-based case-control study carried out in 2011-2013 comprised mothers of 190 incidents (2005-2013) of leukemia/lymphoma cases aged 1-19 yr at diagnosis and 384 population-based controls. Interviews based on a computerized structured questionnaire were conducted with the mothers. Multivariate logistic regression models adjusted for potential confounders assessed the association between breastfeeding patterns and childhood leukemia/lymphoma. Ever breastfeeding category was associated with a 64% decreased risk for childhood leukemia/lymphoma lsqb;odds ratio (OR) = 0.36, 95% confidence interval (CI): 0.22, 0.60lrqb; and similar trends, with a dose-response effect, were observed for any breastfeeding (exclusive and/or partial) category for 6, 12, and 18+ mo. Other infant exposures associated with cancer risk were child iron supplementation (OR = 0.39, 95% CI: 0.26, 0.59), pet ownership (OR = 0.50, 95% CI: 0.33, 0.78), paternal smoking (OR = 1.93, 95% CI: 1.18, 3.15), and having older siblings (OR = 1.18, 95% CI: 1.05, 1.33). Breastfeeding-a controllable and modifiable exposure-is inversely associated with risk for childhood leukemia and lymphoma with a dose-response effect.

Corrigendum: The Associations Between Maternal Factors During Pregnancy and the Risk of Childhood Acute Lymphoblastic Leukemia: A Meta-Analysis

Because of the erroneous application of multiple publications, the conclusions of our recent paper (Pediatr Blood Cancer 2015;62:1162-70) were not reliable. The corrected results show that coffee drinking during pregnancy was risk factor for childhood acute lymphoblastic leukemia (OR = 1.44, 95% confidence interval = 1.07-1.92).

Distribution and features of hematological malignancies in Eastern Morocco: a retrospective multicenter study over 5 years

Background

Hematological malignancies (HM) are a public health problem. The pattern and distribution of diagnosed hematological cancers vary depending on age, sex, geography, and ethnicity suggesting the involvement of genetic and environmental factors for the development of these diseases. To our knowledge, there is no published report on HM in the case of Eastern Morocco. In this report we present for the first time the overall pattern of HM for this region.

Methods

Retrospective descriptive study of patients diagnosed with HM between January 2008 and December 2012 in three centres in Eastern Morocco providing cancer diagnosis, treatment or palliative care services. The FAB (French-American-British) classification system has been taken into account in the analysis of myeloid and lymphoid neoplasms.

Results

In this study, a total of 660 cases of HM were registered between January 2008 and December 2012. Overall, 6075 cases of cancers all sites combined were registered during this study period, indicating that HM account for around 10.9 % (660/6075) of all cancers recorded. Among the 660 registered cases of HM, 53 % were males and 47 % were females, with a male to female ratio of 1.1. Thus, overall, men are slightly more affected with HM than women. By contrast, a female predominance was observed in the case of Hodgkin’s lymphoma (HL), myeloproliferative neoplasms (MPN), acute myeloid leukemia (AML) and the myelodysplastic syndrome (MDS). HM occur at a relatively young age, with an overall median age at diagnosis of 54 years. Non-Hodgkin’s lymphoma (NHL) was the most common HM accounting for 29.7 % of all HM, followed by HL, MPN, multiple myelomas (MM), chronic lymphocytic leukemia (CLL), AML, MDS, acute lymphoblastic leukemia (ALL), and Waldenström macroglobulinemia (WM). The majority of HM cases have been observed among patients aged 60 years and over (40.4 % of HM). Among this age group, NHL was the most common HM. In adolescents, HL was the most frequent HM.

Conclusions

This study provided for the first time the pattern and distribution of HM in Eastern Morocco. Our findings justify the need to establish a regional cancer registry as a first step in blood cancer control in Eastern Morocco.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2205-5) contains supplementary material, which is available to authorized users.

Reported associations between asthma and acute lymphoblastic leukemia: insights from a hybrid simulation study

Numerous studies have reported a protective association between asthma and acute lymphoblastic leukemia (ALL), but the causal structure of this association remains unclear. We present a hybrid simulation to examine the compatibility of this association with uncontrolled confounding by infection or another unmeasured factor. We generated a synthetic cohort using inputs on the interrelations of asthma, ALL, infections, and other suggested risk factors from the literature and the Danish National Birth Cohort. We computed odds ratios (ORs) between asthma and ALL in the synthetic cohort with and without adjustment for infections and other (including unmeasured) confounders. Only if infection was an extremely strong risk factor for asthma (OR of 10) and an extremely strong protective factor against ALL (OR of 0.1) was the asthma-ALL association compatible with the literature (OR of 0.78). Similarly, strong uncontrolled confounding by an unmeasured factor could downwardly bias the asthma-ALL association, but not enough to replicate findings in the literature. This investigation illustrates that the reported protective association between asthma and ALL is unlikely to be entirely due to uncontrolled confounding by infections or an unmeasured confounder alone. Simulation can be used to advance our understanding of risk factors for rare outcomes as demonstrated by this study.

Exposure to maternal smoking during pregnancy and risk of childhood cancer: a study using the Danish national registers

PURPOSE

The relation between maternal smoking during pregnancy and childhood cancer in the offspring remains uncertain. This paper uses Danish national registers, which have collected data prospectively on smoking and cancer, to investigate the association.

METHODS

Smoking during pregnancy was ascertained from maternal self-reported data in the Danish National Patient Register. Index children were followed up from birth until the first of the following events: cancer diagnosis, death, emigration, day before 15th birthday, or end of follow-up. Smoking during pregnancy was considered as a binary variable (no smoking in pregnancy and smoking in pregnancy) and by amounts smoked (no smoking, cessation during pregnancy, ≤5, 6-10, or ≥11 cigarettes/day).

RESULTS

Of the 801,867 children included in the study, 20 % were exposed to maternal smoking during pregnancy. Overall, the hazard ratio (HR) for childhood cancer for the exposed compared to the non-exposed was 0.91 [95 % confidence interval (CI) 0.78, 1.07]. Stratification by number of cigarettes also gave statistically nonsignificant inverse associations. There was a statistically significant increased risk of childhood cancer among children whose mothers reported smoking cessation in pregnancy (HR 1.46; 95 % CI 1.01, 2.10). Regarding specific cancer sites, maternal smoking in pregnancy was positively associated with the risk of eye cancers in childhood.

CONCLUSIONS

Our results do not provide evidence for an association between maternal smoking in pregnancy and childhood cancer overall. An increased risk of childhood cancer was seen for children whose mothers reported smoking cessation in pregnancy. Future research could employ biomarkers, such as cotinine, to validate maternal smoking status recorded in registers as, even if collected prospectively, this self-reported variable may be subject to reporting bias.

Maternal Alcohol Consumption during Pregnancy and Early Age Leukemia Risk in Brazil

Objectives. To investigate the association between the maternal alcohol consumption during pregnancy and early age leukemia (EAL) in offspring. Methods. Datasets were analyzed from a case-control study carried out in Brazil during 1999-2007. Data were obtained by maternal interviews using a standardized questionnaire. The present study included 675 children (193 acute lymphoid leukemia (ALL), 59 acute myeloid leukemia (AML), and 423 controls). Unconditional logistic regression was performed, and adjusted odds ratios (adj. OR) on the association between alcohol consumption and EAL were ascertained. Results. Alcohol consumption was reported by 43% of ALL and 39% of AML case mothers and 35.5% of controls'. Beer consumption before and during pregnancy was associated with ALL in crude analysis (OR = 1.54, 95% CI, 1.08-2.19), although in adjusted analysis no statistical significance was found. For weekly intake of ≤1 glass (adj. OR = 1.30, 95% CI, 0.71-2.36) and ≥1 glass/week (adj. OR = 1.47, 95% CI, 0.88-2.46) a potential dose-response was observed (P trend < 0.03). Conclusion. This study failed to support the hypothesis of an increased risk of EAL associated with maternal alcohol intake during pregnancy, neither with the interaction with tobacco nor with alcohol consumption.

ARID5B, IKZF1 and non-genetic factors in the etiology of childhood acute lymphoblastic leukemia: the ESCALE study

Genome-wide association studies (GWAS) have identified that frequent polymorphisms in ARID5B and IKZF1, two genes involved in lymphoid differentiation, increase the risk of childhood acute lymphoblastic leukemia (ALL). These findings markedly modified the current field of research on the etiology of ALL. In this new context, the present exploratory study investigated the possible interactions between these at-risk alleles and the non-genetic suspected ALL risk factors that were of sufficient prevalence in the French ESCALE study: maternal use of home insecticides during pregnancy, preconception paternal smoking, and some proxies for early immune modulation, i.e. breastfeeding, history of common infections before age one year, and birth order. The analyses were based on 434 ALL cases and 442 controls of European origin, drawn from the nationwide population-based case-control study ESCALE. Information on non-genetic factors was obtained by standardized telephone interview. Interactions between rs10740055 in ARID5B or rs4132601 in IKZF1 and each of the suspected non-genetic factors were tested, with the SNPs coded as counts of minor alleles (trend variable). Statistical interactions were observed between rs4132601 and maternal insecticide use (p = 0.012), breastfeeding p = 0.017) and repeated early common infections (p = 0.0070), with allelic odds ratios (OR) which were only increased among the children not exposed to insecticides (OR = 1.8, 95%CI: 1.3, 2.4), those who had been breastfed (OR = 1.8, 95%CI: 1.3, 2.5) and those who had had repeated early common infections (OR = 2.4, 95%CI: 1.5, 3.8). The allelic ORs were close to one among children exposed to insecticides, who had not been breastfed and who had had no or few common infections. Repeated early common infections interacted with rs10740055 (p = 0.018) in the case-only design. Further studies are needed to evaluate whether these observations of a modification of the effect of the at-risk alleles by non-genetic factors are chance findings or reflect true underlying mechanisms.

SETIL: Italian multicentric epidemiological case-control study on risk factors for childhood leukaemia, non hodgkin lymphoma and neuroblastoma: study population and prevalence of risk factors in Italy

BACKGROUND

Aetiology of childhood leukaemia and childhood neoplasm is poorly understood. Information on the prevalence of risk factors in the childhood population is limited. SETIL is a population based case-control study on childhood leukaemia, conducted with two companion studies on non-Hodgkin Lymphoma (NHL) and neuroblastoma. The study relies on questionnaire interviews and 50 Hz magnetic field (ELF-MF) indoor measurements. This paper discusses the SETIL study design and includes descriptive information.

METHODS

The study was carried out in 14 Italian regions (78.3% of Italian population aged 0-10). It included leukaemia, NHL and neuroblastoma cases incident in 0-10 year olds in 1998-2001, registered by the Italian Association of Paediatric Haematology and Oncology (AIEOP) (accrual over 95% of estimated incidence). Two controls for each leukaemia case were randomly sampled from the Local Health Authorities rolls, matched by gender, birthdate and residence. The same controls were used in NHL and neuroblastoma studies. Parents were interviewed at home on: physical agents (ELF-MF and ionizing radiation), chemicals (smoking, solvents, traffic, insecticides), occupation, medical and personal history of children and parents, infectious diseases, immunizations and associated factors. Occupational exposure was collected using job specific modules. ELF-MF was measured in the main rooms (spot measurement) and close to child's bed (48 hours measurement).

RESULTS

The study included: 683 leukaemia cases (87% ALL, 13% AnLL), 97 NHL, 155 neuroblastomas, and 1044 controls.

CONCLUSIONS

SETIL represents a data source on exposure of Italian children to a broad array of potential carcinogenic factors.

Maternal benzene exposure during pregnancy and risk of childhood acute lymphoblastic leukemia: a meta-analysis of epidemiologic studies

Background

The prevalence of childhood leukemia is increasing rapidly all over the world. However, studies on maternal benzene exposure during pregnancy and childhood acute lymphoblastic leukemia (ALL) have not been systematically assessed. Therefore, we performed a meta-analysis to investigate the association between maternal solvent, paint, petroleum exposure, and smoking during pregnancy and risk of childhood ALL.

Methods

Relevant studies up to September 1^st, 2013 were identified by searching the PubMed, EMBASE, Cochrane library and the Web of Science databases. The effects were pooled using either fixed or random effect models based on the heterogeneity of the studies.

Results

Twenty-eight case-control studies and one cohort study were included for analysis, with a total of 16,695 cases and 1,472,786 controls involved. Pooled odds ratio (OR) with 95% confidence interval (CI) for ALL was 1.25 (1.09, 1.45) for solvent, 1.23 (1.02, 1.47) for paint, 1.42 (1.10, 1.84) for petroleum exposure, and 0.99 (0.93, 1.06) for maternal smoking during pregnancy. No publication bias was found in this meta-analysis and consistent results were observed for subgroup and sensitivity analyses.

Conclusions

Childhood ALL was associated with maternal solvent, paint, and petroleum exposure during pregnancy. No association was found between ALL and maternal smoking during pregnancy. Avoidance of maternal occupational and environmental benzene exposure during pregnancy could contribute to a decrease in the risk of childhood ALL.

Tobacco or healthy children: the two cannot co-exist

Tobacco exposure increases mortality and morbidity of the fetus, the child, the adolescent, and their children in turn. Nearly half the children in the world are exposed. Smoking is not merely personal choice or personal responsibility; those subtle phrases undermine those who have no choice in the matter. Tobacco control must take a multi-pronged attack. Smoking cessation by adults in childbearing years must take center stage of these efforts, because it is the only way to ensure a smoke-free environment for children. Smoke-free parents provide a role model for smoke-free young people, and erode the image of smoking as a desirable adult behavior to emulate. Pediatricians and pediatric pulmonologists have a key role to play here. This goal will reduce morbidity and mortality among adults and children. Legislation regarding taxation, environments, tobacco constituents, product placement and display, packaging, and media education are all key to this core goal. Smoke-free policy must be protected from attack based on trade agreements. Research is needed into more effective ways to attract and help people give up smoking, and into educating and re-deploying tobacco industry workers in emerging and developed countries.

Epidemiology of childhood acute myeloid leukemia

Although leukemia is the most common childhood cancer diagnosis, the subtype, acute myeloid leukemia (AML), is less common and fewer etiologic studies exist. This review summarizes the major risk factors for AML. We searched the literature using PubMed for articles on childhood AML and reviewed 180 articles. While few risk factors are definitive, we identified several with consistent evidence of a possible effect. Thorough analysis of genetic and epigenetic factors is missing from this literature and methodological issues are unresolved. Future studies should more closely examine causal mechanisms, improve exposure measurement, and include analysis using genetic and epigenetic factors.

Fertility treatments, congenital malformations, fetal loss, and childhood acute leukemia: the ESCALE study (SFCE)

BACKGROUND

This study investigated the relationships between childhood acute leukemia (AL) and selective maternal and birth characteristics, including congenital malformations and the use of fertility treatment, for which the literature remains scarce.

PROCEDURE

The national registry-based case-control study ESCALE was carried out in France in 2003-2004. Population controls were frequency matched with cases on age and gender. Data were obtained from structured telephone questionnaires. Odds ratios (OR) and their 95% confidence intervals were estimated using unconditional regression models adjusted for potential confounders.

RESULTS

In all, 764 cases of AL (648 lymphoblastic AL (acute lymphoblastic leukemia, ALL) and 101 myeloblastic AL) and 1,681 controls were included. The AL cases' mothers reported congenital malformations more frequently than the controls' mothers (OR = 1.5 [1.0-2.4]). ALL was significantly associated with the use of fertility treatment for the index pregnancy (OR = 1.9 [1.3-2.8]). In particular, ALL was associated with ovulation induction only (OR = 2.6 [1.6-4.3]), but not with in vitro fertilization (IVF, OR = 1.0 [0.4-2.3]) or artificial insemination (OR = 1.3 [0.5-3.9]). A positive association was also observed for the difficulty of becoming pregnant without fertility treatment (OR = 1.5 [1.0-2.1]). AL was positively associated with a history of voluntary abortion (OR = 1.4 [1.1-1.8]) but not with a history of spontaneous (OR = 0.8 [0.7-1.0]) or therapeutic (OR = 0.7 [0.5-1.1]) abortion.

CONCLUSION

The results suggest that subfertility in itself and ovulation induction may be associated with ALL, and support a positive association with congenital malformations. The links with the various types of fertility drugs and the underlying causes of infertility need to be investigated further.

Pregnancy, maternal tobacco smoking, and early age leukemia in Brazil

BACKGROUND

Cigarette smoking has been associated with acute myeloid leukemia (AML) but hypothesis on the association between maternal smoking during pregnancy and childhood leukemia remains unclear.

OBJECTIVES

To investigate the association between maternal exposure to tobacco smoking during pregnancy and early age (<2 year) leukemia (EAL).

METHODS

A hospital-based multicenter case-control study aiming to explore EAL risk factors was carried out in Brazil during 1999-2007. Data were collected by direct interview with the biological mothers using a standardized questionnaire. The present study included 675 children (193 acute lymphoid leukemia - ALL, 59 AML and 423 controls), being the latter age frequency matched and paired by area of residence with the cases. Unconditional logistic regression was performed, and odds ratios (OR) on the association between tobacco smoking (3 months before pregnancy, during pregnancy, and 3 months after delivery) and EAL were ascertained after adjustment for selected variables (maternal age at birth and education, birth weight, infant skin color, and oral contraceptives use during pregnancy).

RESULTS

Smoking was reported by 17.5% of case mothers and 20.6% of controls. Among women who reported to have smoked 20 or more cigarettes during the index pregnancy, an adjusted OR = 5.28 (95% CI 1.40-19.95) for ALL was observed. Heavy smoking during breastfeeding yielded an adjusted risk estimate for ALL, OR = 7.78 (95% CI 1.33-45.5). No dose-response effect was observed according to smoking exposure during pregnancy and EAL. An association between secondhand smoking during pregnancy or breastfeeding was not observed.

CONCLUSION

An association between maternal smoking and EAL in the offspring was restricted to women who have reported an intense exposure to tobacco smoke during pregnancy and breastfeeding.

Folic acid supplementation, MTHFR and MTRR polymorphisms, and the risk of childhood leukemia: the ESCALE study (SFCE)

PURPOSE

Fetal folate deficiency may increase the risk of subsequent childhood acute leukemia (AL), since folates are required for DNA methylation, synthesis, and repair, but the literature remains scarce. This study tested the hypothesis that maternal folic acid supplementation before or during pregnancy reduces AL risk, accounting for the SNPs rs1801133 (C677T) and rs1801131 (A1298C) in MTHFR and rs1801394 (A66G) and rs1532268 (C524T) in MTRR, assumed to modify folate metabolism.

METHODS

The nationwide registry-based case-control study, ESCALE, carried out in 2003-2004, included 764 AL cases and 1,681 controls frequency matched with the cases on age and gender. Information on folic acid supplementation was obtained by standardized telephone interview. The genotypes were obtained using high-throughput platforms and imputation for untyped polymorphisms. Odds ratios (OR) were estimated using unconditional regression models adjusted for potential confounders.

RESULTS

AL was significantly inversely associated with maternal folic acid supplementation before and during pregnancy (OR = 0.4; 95 % confidence interval: [0.3-0.6]). MTHFR and MTRR genetic polymorphisms were not associated with AL. However, AL was positively associated with homozygosity for any of the MTHFR polymorphisms and carriership of both MTRR variant alleles (OR = 1.6 [0.9-3.1]). No interaction was observed between MTHFR, MTRR, and maternal folate supplementation.

CONCLUSION

The study findings support the hypothesis that maternal folic acid supplementation may reduce the risk of childhood AL. The findings also suggest that the genotype homozygous for any of the MTHFR variants and carrying both MTRR variants could be a risk factor for AL.

Variation in xenobiotic transport and metabolism genes, household chemical exposures, and risk of childhood acute lymphoblastic leukemia

Background

Recent studies suggest that environmental exposures to pesticides, tobacco, and other xenobiotic chemicals may increase risk of childhood acute lymphoblastic leukemia (ALL). We sought to evaluate the role of genes involved in xenobiotic transport and metabolism in childhood ALL risk, both alone and in conjunction with household chemical exposures previously found to be associated with childhood ALL risk.

Methods

We conducted a population-based epidemiologic study of 377 cases and 448 controls in California, utilizing a haplotype-based approach to evaluate 42 xenobiotic transport and metabolism genes in conjunction with data on self-reported household chemical exposures.

Results

We identified significant associations of childhood ALL risk with haplotypes of ABCB1, ARNT, CYP2C8, CYP1A2, CYP1B1, and IDH1. In addition, certain haplotypes showed significant joint effects with self-reported household chemical exposures on risk of childhood ALL. Specifically, elevated risks associated with use of paints in the home (ever) and indoor insecticides (pre-birth) were limited to subjects carrying specific haplotypes of CYP2C8 and ABCB1, respectively.

Conclusions

Our results provide support for a role of xenobiotic transport and metabolism pathways in risk of childhood ALL and indicate that genes in these pathways may modulate the risk of disease associated with use of common household chemicals. Additional studies are needed to confirm these findings and localize specific causal variants.

Electronic supplementary material

The online version of this article (doi:10.1007/s10552-012-9947-4) contains supplementary material, which is available to authorized users.

Maternal smoking during pregnancy and risk for childhood leukemia: a nationwide case-control study in Greece and meta-analysis

BACKGROUND

Maternal smoking during pregnancy has been often implicated in the development of childhood leukemia with ambiguous results. Hence, we conducted a meta-analysis aiming to summarize current evidence and quantify any tentative impact.

PROCEDURE

We retrieved one cohort (553 leukemias compared to 1,440,542 children), 20 case-control studies and also analyzed the updated Greek case-control dataset with unpublished data, yielding in total 11,092 cases and 25,221 controls.

RESULTS

Odds ratios reported in the studies included ranged from 0.70 to 2.20 for acute lymphocytic (ALL) and from 0.60 to 2.17 for acute myelocytic leukemia (AML). The combined effect regarding the association of maternal smoking (any vs. no) and leukemia risk was 1.03 for ALL (95% CI = 0.95-1.12, random effects model) and 0.99 for AML (95% CI = 0.90-1.09, fixed effects model). The results remained unchanged when sensitivity analyses were undertaken of studies reporting same maternal smoking periods, those focusing only on childhood leukemia deaths or investigations which did not clearly define AML subtype.

CONCLUSIONS

The findings of the meta-analysis challenge the limits of traditional epidemiology to provide sound inferences when point estimates of constituent studies range around the null. In particular, this study provides no support to a hypothesis linking maternal smoking during pregnancy with subsequent development of main childhood leukemia subtypes. Further investigations employing molecular and genetic epidemiology, however, might be needed in the hope to reveal even minimal risks pertaining individuals with specific susceptibility to tobacco compounds who sustain high environmental exposures prenatally or postnatally.

Parental prenatal smoking and risk of childhood acute lymphoblastic leukemia

The association between parental smoking and risk of childhood acute lymphoblastic leukemia (ALL) was investigated in an Australian population-based case-control study that included 388 cases and 868 controls aged <15 years, recruited from 2003 to 2006. Both of the child's parents provided information about their smoking habits for each year from age 15 years to the child's birth. Data were analyzed by logistic regression. Maternal smoking was not associated with risk of childhood ALL, but the odds ratio for paternal smoking of ≥15 cigarettes per day around the time of the child's conception was 1.35 (95% confidence interval: 0.98, 1.86). The associations between parental smoking risk of childhood ALL did not differ substantially by immunophenotypic or cytogenetic subtype. Meta-analyses of paternal smoking, including results from the Australian Study of Causes of Acute Lymphoblastic Leukemia in Children and those of previous studies, produced summary odds ratios of 1.15 (95% confidence interval: 1.06, 1.24) for any paternal smoking around the time of the child's conception and 1.44 (95% confidence interval: 1.24, 1.68) for smoking ≥20 cigarettes per day at that time. Study results suggest that heavier paternal smoking around the time of conception is a risk factor for childhood ALL. Men should be strongly encouraged to cease smoking, particularly when planning to start a family.

[The Fetal Tobacco Syndrome - A statement of the Austrian Societies for General- and Family Medicine (ÖGAM), Gynecology and Obstetrics (ÖGGG), Hygiene, Microbiology and Preventive Medicine (ÖGHMP), Pediatrics and Adolescence Medicine (ÖGKJ) as well as Pneumology (ÖGP)]

Over more than 50 years, the nocuous effects of smoking in pregnancy on the fetus are well known. In the first years of science the focus was primarily on restricted fetal growth while in more recent years over 10.000 studies investigated the incomparably big sum of detrimental effects for the unborn's health. In this statement we want to present the recent scientific findings on this topic. The statement is aimed to show all doctors who treat pregnant women the present situation and evidence. In the beginning we give a short overview about the epidemiological situation in Europe. Then we present step by step the health effects with regards to pathophysiology and clinics. Furthermore the reader will learn about possibilities for smoking cessation in pregnancy. The problem of passive-smoking in pregnancy will be dealt with in a separate chapter. At present there is strong evidence that pregnant smoking has a detrimental effect on birth-weight, placenta-associated disease, stillbirth, sudden infant death syndrome (SIDS), childhood overweight, clefts, lung function, asthma, cardiovascular diseases and mental developmental disorders. These factors can be summarized by the term Fetal Tobacco Syndrome. There is supply for more studies for less investigated health effects. Pregnancy is a chance to stop smoking as most women show a high motivation in this period. Hence doctors of all disciplines should inform pregnant women about the detrimental effects of smoking on their unborn child and show them possibilities for smoking cessation.

Refuelling of vehicles, the use of wood burners and the risk of acute lymphoblastic leukaemia in childhood

It is plausible that exposure of the parents before birth or of the child to sources of benzene increases the risk of childhood acute lymphoblastic leukaemia (ALL). The aim of this analysis was to investigate whether refuelling a vehicle with petrol before birth or burning wood to heat the home before or after the child's birth increased the risk of childhood ALL. Data from 389 cases and 876 frequency-matched controls were analysed using unconditional logistic regression, adjusting for study matching factors and potential confounders. The odds ratio (OR) for the mother ever refuelling a vehicle with petrol for non-occupational purposes before or during the pregnancy was 0.97 [95% confidence interval (CI) 0.69, 1.38]. The OR for the father for this exposure in the year before conception was 0.88 [95% CI 0.52, 1.48]. The OR for use of a closed wood burner to heat the home in the year before or during pregnancy was 1.41 [95% CI 1.02, 1.94] and 1.25 [95% CI 0.92, 1.70] after birth. We found no evidence that non-occupational refuelling a vehicle with petrol in the year before or during pregnancy increased the risk of ALL in the offspring. There was weak evidence that burning wood in a closed burner to heat the home increased the risk, but there was no dose-response relationship and chance could explain the finding.

Paternal smoking and risk of childhood acute lymphoblastic leukemia: systematic review and meta-analysis

Objective. To investigate the association between paternal smoking and childhood acute lymphoblastic leukemia (ALL). Method. We identified 18 published epidemiologic studies that reported data on both paternal smoking and childhood ALL risk. We performed a meta-analysis and analyzed dose-response relationships on ALL risk for smoking during preconception, during pregnancy, after birth, and ever smoking. Results. The summary odds ratio (OR) of childhood ALL associated with paternal smoking was 1.11 (95% Confidence Interval (CI): 1.05-1.18, I(2) = 18%) during any time period, 1.25 (95% CI: 1.08-1.46, I(2) = 53%) preconception; 1.24 (95% CI: 1.07-1.43, I(2) = 54%) during pregnancy, and 1.24 (95% CI: 0.96-1.60, I(2) = 64%) after birth, with a dose-response relationship between childhood ALL and paternal smoking preconception or after birth. Conclusion. The evidence supports a positive association between childhood ALL and paternal ever smoking and at each exposure time period examined. Future epidemiologic studies should assess paternal smoking during well-defined exposure windows and should include biomarkers to assess smoking exposure and toxicological mechanisms.

hOGG1 Ser326Cys polymorphism and risk of childhood acute lymphoblastic leukemia in a Chinese population

Oxidative DNA damage caused by reactive oxygen species can produce 8-oxoguanine (8-oxoG) in DNA, which is misread and leads to G:C→T:A transversions. This can be carcinogenic. Repair of 8-oxoG by the base excision repair pathway involves the activity of human 8-oxoG DNA glycosylase 1 (hOGG1). Accumulating evidence suggests that the hOGG1 Ser326Cys polymorphism affects the activity of hOGG1 and might serve as a genetic marker for susceptibility to several cancers. To determine whether this polymorphism is associated with risk of childhood acute lymphoblastic leukemia (ALL) in Chinese children, we genotyped the hOGG1 Ser326Cys polymorphism (rs1052133) in a case-control study including 415 cases and 511 controls. We found that there was a significant difference in the genotype distributions of the hOGG1 Ser326Cys polymorphism between cases and controls (P = 0.046), and the combined genotypes Ser/Ser and Ser/Cys were associated with a statistically significantly decreased risk of ALL (adjusted odds ratio [OR] = 0.66, 95% confidence interval [CI] = 0.49-0.88, P = 0.005). Furthermore, we found a decreased risk for high risk ALL (adjusted OR = 0.60, 95% CI = 0.40-0.88, P = 0.005), low risk ALL (adjusted OR = 0.68, 95% CI = 0.47-0.99, P = 0.042), and B-phenotype ALL (adjusted OR = 0.63, 95% CI = 0.46-0.86, P = 0.003) among children with the Ser/Ser and Ser/Cys genotypes. Our results suggest that the hOGG1 Ser326Cys polymorphism is associated with susceptibility to childhood ALL in a Chinese population.

Childhood Hodgkin's lymphoma, non-Hodgkin's lymphoma and factors related to the immune system: the Escale Study (SFCE)

The study investigated the role of factors considered related to the early stimulation of the immune system in the aetiology of childhood lymphoma. The national registry-based case-control study, Escale, was carried out in France over the period 2003-2004. Population controls were frequency matched with the cases on age and gender. Data were obtained from structured telephone questionnaires administered to mothers. Odds ratios (ORs) were estimated using unconditional regression models adjusted for potential confounders. Data from 128 cases of Hodgkin's lymphoma (HL) aged 5-14 years, 164 cases of non-Hodgkin's lymphoma (NHL) aged 2-14 years and 1,312 controls were analyzed. Negative associations were observed between HL and day care attendance [OR = 0.5 (0.2-1.2)] and between HL and repeated early common infections among non-breastfed children [OR = 0.3 (.2-0.7), p = 0.003] [OR for breastfed children: 1.0 (.5-2.1)], but not for the other factors investigated. Negative associations were observed between NHL and birth order 3 or more [OR = 0.7 (0.4-1.1)], prolonged breastfeeding [OR = 0.5 (0.3-1.0)], regular contact with farm animals [OR = 0.5 (0.3-1.0)], frequent farm visits in early life [OR = 0.6 (0.4-1.1)] and history of asthma [OR = 0.6 (0.3-1.1)]. In conclusion, the results partly support the hypothesis that an abnormal maturation of the immune system may play a role in childhood HL or NHL, and call for further investigations.

Road traffic and childhood leukemia: the ESCALE study (SFCE)

BACKGROUND

Traffic is a source of environmental exposures, including benzene, which may be related to childhood leukemia.

OBJECTIVES

A national registry-based case-control study [ESCALE (Etude Sur les Cancers et les Leucémies de l'Enfant, Study on Environmental and Genetic Risk Factors of Childhood Cancers and Leukemia)] carried out in France was used to assess the effect of exposure to road traffic exhaust fumes on the risk of childhood leukemia.

METHODS

Over the study period, 2003-2004, 763 cases and 1,681 controls < 15 years old were included, and the controls were frequency matched with the cases on age and sex. The ESCALE data were collected by a standardized telephone interview of the mothers. Various indicators of exposure to traffic and pollution were determined using the geocoded addresses at the time of diagnosis for the cases and of interview for the controls. Indicators of the distance from, and density of, main roads and traffic nitrogen dioxide (NO(2)) concentrations derived from traffic emission data were used. Odds ratios (ORs) were estimated using unconditional regression models adjusted for potential confounders.

RESULTS

Acute leukemia (AL) was significantly associated with estimates of traffic NO(2) concentration at the place of residence > 27.7 µg/m(3) compared with NO(2) concentration < 21.9 µg/m(3) [OR=1.2; confidence interval (CI), 1.0-1.5] and with the presence of a heavy-traffic road within 500 m compared with the absence of a heavy-traffic road in the same area (OR=2.0; 95% CI, 1.0-3.6). There was a significant association between AL and a high density of heavy-traffic roads within 500 m compared with the reference category with no heavy-traffic road within 500 m (OR=2.2; 95% CI, 1.1-4.2), with a significant positive linear trend of the association of AL with the total length of heavy-traffic road within 500 m.

CONCLUSION

This study supports the hypothesis that living close to heavy-traffic roads may increase the risk of childhood leukemia.

Maternal smoking during pregnancy and childhood lymphoma: a meta-analysis

Results from epidemiological studies exploring the association between childhood lymphoma and maternal smoking during pregnancy have been contradictory. This meta-analysis included all published cohort (n = 2) and case-control (n = 10) articles; among the latter, the data of the Greek Nationwide Registry for Childhood Hematological Malignancies study were updated to include all recently available cases (-2008). Odds ratios (ORs), relative risks and hazard ratios were appropriately pooled in three separate analyses concerning non-Hodgkin lymphoma (NHL, n = 1,072 cases), Hodgkin lymphoma (HL, n = 538 cases) and any lymphoma (n = 1,591 cases), according to data availability in the included studies. An additional metaregression analysis was conducted to explore dose-response relationships. A statistically significant association between maternal smoking (any vs. no) during pregnancy and risk for childhood NHL was observed (OR = 1.22, 95% confidence interval, CI: 1.03-1.45, fixed effects model), whereas the risk for childhood HL was not statistically significant (OR = 0.90, 95% CI: 0.66-1.21, fixed effects model). The analysis on any lymphoma did not reach statistical significance (OR = 1.10, 95% CI = 0.96-1.27, fixed effects model), possibly because of the case-mix of NHL to HL. No dose-response association was revealed in the metaregression analysis. In conclusion, this meta-analysis points to a modest increase in the risk for childhood NHL, but not HL, among children born by mothers smoking during pregnancy. Further investigation of dose-response phenomena in the NHL association, however, warrants accumulation of additional data.