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

Association Between Perinatal Factors and Childhood Lymphoma-A Pooled Analysis of the ESCALE and ESTELLE Studies (SFCE)

CONTEXT

There is much interest in the perinatal period in relation to childhood cancer aetiology, with most studies focussing on childhood leukaemia. This work aimed to investigate the associations between pregnancy-related and perinatal factors and childhood lymphoma.

METHODS

We conducted a pooled analysis of two French nationwide population-based case-control studies. Data on sociodemographic, perinatal and lifestyle factors were collected through maternal interviews. Odds ratios (OR) and 95% confidence intervals (CIs) were computed using adjusted logistic regression models, separately for non-Hodgkin lymphoma (NHL) and Hodgkin lymphoma (HL). Specific analyses also investigated Burkitt NHL and nodular sclerosis HL, two most common histological types in children.

RESULTS

We included 305 NHL, 328 HL and 2415 controls in this study. No associations were observed with gestational age, foetal growth indicators, folic acid supplementation, factors related to maternal fertility and reproductive history, or maternal smoking during pregnancy. Maternal coffee consumption during pregnancy was associated with NHL (>2 cups/day, OR = 1.5 [95% CI: 1.1-2.1]), with a dose-response relationship; while maternal alcohol consumption was associated with Burkitt NHL (OR = 1.5 [1.1-2.2]). Paternal smoking during preconception/pregnancy was associated with NHL (OR = 1.4 [1.1-1.8]). Breastfeeding (ever/never) was not significantly associated with NHL and HL, but an inverse log-linear trend was observed with the duration of breastfeeding for NHL (p = 0.04).

CONCLUSION

Maternal coffee and alcohol consumptions during pregnancy and paternal smoking during preconception/pregnancy might increase the risk of childhood NHL. While warranting replication, these findings could help us better understand the aetiology of childhood lymphoma.

Breastfeeding and the risk of childhood cancer: a systematic review and dose-response meta-analysis

BACKGROUND

The aim of this study was to quantitatively summarize the available evidence on the association of breastfeeding with the risk of childhood cancer.

METHODS

A literature search of PubMed and Embase databases was performed to identify eligible observational studies published from inception to July 17, 2020. The categorical and dose-response meta-analysis was conducted by pooling relative risk (RR) or odds ratio (OR) estimates with 95% confidence intervals (CIs). Potential sources of heterogeneity were detected by meta-regression and stratification analysis. Sensitivity analysis and publication bias test were also carried out.

RESULTS

Forty-five articles involving 475,579 individuals were included in the meta-analysis. Among the thirty-three studies on the association between breastfeeding and risk of childhood leukemia, the pooled risk estimates were 0.77 (95% CI, 0.65-0.91) and 0.77 (95% CI 0.63-0.94) for ever versus non/occasional breastfeeding and longest versus shortest breastfeeding duration group, respectively. There was clear indication for non-linear dose-response relationship between breastfeeding duration and the risk of childhood leukemia (P non-linear < 0.001). The most protective effect (OR, 0.66, 95% CI 0.62-0.70) was observed at a breastfeeding duration of 9.6 months. Four studies examined, the association between breastfeeding and risk of childhood neuroblastoma, and significant inverse associations were consistently observed in both the comparisons of ever breastfeeding versus non/occasional breastfeeding (OR = 0.59, 95% CI 0.44-0.81) and longest versus shortest breastfeeding (OR = 0.61, 95% CI 0.44-0.83). However, no associations of breastfeeding with risk of other cancers were found.

CONCLUSIONS

Our study supports a protective role of breastfeeding on the risk of childhood leukemia, also suggesting a non-linear dose-response relationship. Further studies are warranted to confirm the association between breastfeeding and risk of childhood neuroblastoma.

Health outcomes of smoking during pregnancy and the postpartum period: an umbrella review

BACKGROUND

Smoking during pregnancy (SDP) and the postpartum period has serious health outcomes for the mother and infant. Although some systematic reviews have shown the impact of maternal SDP on particular conditions, a systematic review examining the overall health outcomes has not been published. Hence, this paper aimed to conduct an umbrella review on this issue.

METHODS

A systematic review of systematic reviews (umbrella review) was conducted according to a protocol submitted to PROSPERO ( CRD42018086350 ). CINAHL, EMBASE, MEDLINE, PsycINFO, Web of Science, CRD Database and HMIC databases were searched to include all studies published in English by 31 December 2017, except those focusing exclusively on low-income countries. Two researchers conducted the study selection and quality assessment independently.

RESULTS

The review included 64 studies analysing the relationship between maternal SDP and 46 health conditions. The highest increase in risks was found for sudden infant death syndrome, asthma, stillbirth, low birth weight and obesity amongst infants. The impact of SDP was associated with the number of cigarettes consumed. According to the causal link analysis, five mother-related and ten infant-related conditions had a causal link with SDP. In addition, some studies reported protective impacts of SDP on pre-eclampsia, hyperemesis gravidarum and skin defects on infants. The review identified important gaps in the literature regarding the dose-response association, exposure window, postnatal smoking.

CONCLUSIONS

The review shows that maternal SDP is not only associated with short-term health conditions (e.g. preterm birth, oral clefts) but also some which can have life-long detrimental impacts (e.g. obesity, intellectual impairment).

IMPLICATIONS

This umbrella review provides a comprehensive analysis of the overall health impacts of SDP. The study findings indicate that while estimating health and cost outcomes of SDP, long-term health impacts should be considered as well as short-term effects since studies not including the long-term outcomes would underestimate the magnitude of the issue. Also, interventions for pregnant women who smoke should consider the impact of reducing smoking due to health benefits on mothers and infants, and not solely cessation.

Maternal exposure to pesticides and risk of childhood lymphoma in France: A pooled analysis of the ESCALE and ESTELLE studies (SFCE)

BACKGROUND

Few studies have assessed the relation between maternal prenatal pesticides use and childhood lymphoma risk, some reporting a positive association with non-Hodgkin lymphoma (NHL). We investigated the association between maternal exposure to pesticides during pregnancy and childhood Hodgkin (HL) and non-Hodgkin lymphoma.

METHODS

We pooled data from the two French national population-based case-control studies ESCALE (2003-2004) and ESTELLE (2010-2011). Data on domestic and occupational exposures to pesticides during pregnancy were obtained through standardised maternal interviews. Logistic regression models were used to compute odds ratios (OR) and 95% confidence intervals (CI) for HL and NHL, by pesticide category adjusted for potential confounders. Analyses by histological subtypes were also performed.

RESULTS

We included 328 H L, 305 non-Hodgkin NHL and 2,415 controls. Around 40% of control mothers reported having used pesticides during index pregnancy, of whom 95% reported insecticides use. Maternal use of herbicides and fungicides occurred mostly in combination with insecticides. Insecticides use was more frequently reported in cases than controls (OR_NHL = 1.6 [95%CI 1.3-2.1], p = 0.0001; OR_HL = 1.3 [95%CI 1.0-1.7], p = 0.03). This association appeared more marked for Burkitt lymphoma and mixed cellularity classical HL. No obvious association was observed with occupational pesticides exposure during pregnancy.

CONCLUSION

These results suggest that maternal domestic use of insecticides during pregnancy might be related to both childhood NHL and HL. Further larger studies are urgently needed.

Exposure to Tobacco, Environmental Tobacco Smoke and Nicotine in Pregnancy: A Pragmatic Overview of Reviews of Maternal and Child Outcomes, Effectiveness of Interventions and Barriers and Facilitators to Quitting

The aim of this review of reviews was to collate the latest evidence from systematic reviews about the maternal and child health outcomes of being exposed to tobacco and nicotine during pregnancy; the effectiveness of interventions designed to reduce these exposures, and barriers to and facilitators of smoking cessation during pregnancy. Two databases were searched to obtain systematic reviews published from 2010 to 2019. Pertinent data from 76 articles were summarized using a narrative synthesis (PROSPERO reference: CRD42018085896). Exposure to smoke or tobacco in other forms during pregnancy is associated with an increased risk of obstetric complications and adverse health outcomes for children exposed in-utero. Counselling interventions are modestly effective, while incentive-based interventions appear to substantially increase smoking cessation. Nicotine replacement therapy is effective during pregnancy but the evidence is not conclusive. Predictors and barriers to smoking cessation in pregnancy are also discussed. Smoking during pregnancy poses substantial risk to mother's and child's health. Psychosocial interventions and nicotine replacement therapy (NRT) appear to be effective in helping pregnant women quit smoking. Barriers to smoking cessation must be identified and steps taken to eradicate them in order to reduce smoking among pregnant women. More research is needed on smoking cessation medications and e-cigarettes.

Parental alcohol consumption and risk of leukemia in the offspring: a systematic review and meta-analysis

Parental alcohol consumption before and during pregnancy has been linked to adverse outcomes in the offspring including leukemogenesis. We, therefore, aimed to systematically assess and quantitatively synthesize published data on the association of paternal consumption during preconception and maternal consumption during pregnancy with leukemia risk in childhood (0-14 years). Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we searched PubMed (until February 2016) and the reference lists of the relevant studies. Observational studies examining the association between parental alcohol consumption and childhood leukemia were considered eligible. Data extracted from 39 case-control studies (over 16 000 leukemia cases and 30 000 controls) were pooled and summary-effect estimates were calculated. Subgroup analyses were carried out by main acute leukemia type [lymphoblastic or myeloid), cytogenetics/genetic polymorphisms, and specific alcohol beverages. We found a statistically significant dose-response association of any level of maternal alcohol consumption compared with nondrinking during pregnancy exclusively with acute myeloid leukemia (AML) [odds ratio (OR)moderate consumption: 1.64, 95% confidence intervals (CIs): 1.23-2.17 and ORhigh consumption: 2.36, 95% CI: 1.60-3.49]. In contrast, no association of paternal preconception consumption with any leukemia type was noted. In beverage-specific analyses, only a positive association of maternal wine drinking with childhood AML was found, which was more pronounced in analyses including only studies on infant leukemia (ORwine: 2.12, 95% CI: 1.16-3.90). The largest ever meta-analysis shows a sizeable, statistically significant dose-response association of maternal alcohol consumption during index pregnancy with AML risk. Future research exploring the role of genetic polymorphisms is anticipated to shed light on the underlying pathophysiology.

Postnatal Cardiovascular Consequences in the Offspring of Pregnant Rats Exposed to Smoking and Smoking Cessation Pharmacotherapies

Approximately 20% of pregnant women smoke despite intentions to quit. Smoking cessation drugs, such as nicotine replacement therapy (NRT) and bupropion, are recommended treatments. Adverse cardiovascular outcomes in offspring have raised concerns about NRT's safety during pregnancy. However, the effect of bupropion is unknown. Using a rat model, we determined whether NRT and bupropion interventions during pregnancy are safer than continued smoking on offspring's cardiovascular function. Male offspring of controls and dams exposed to cigarette smoke (1.6 packs/day, inhalation), nicotine (2 mg/kg/d subcutaneously), and bupropion (13 mg/kg twice daily orally) were assessed for fetoplacental weight, cardiac function, blood pressure, and vascular reactivity. Fetoplacental weights were decreased and spontaneous beating and intracellular calcium in neonatal cardiomyocytes were increased in smoking, nicotine, and bupropion offspring; however, these effects were more accentuated in smoking followed by nicotine and bupropion offspring. Increased heart rate and decreased cardiac output, stroke volume, and left ventricular percent posterior wall thickening were observed in smoking, nicotine, and bupropion offspring. The left ventricular mass was reduced in smoking and nicotine but not in bupropion offspring. Blood pressure was higher with decreased endothelium-dependent relaxation and exaggerated vascular contraction to angiotensin II in smoking and nicotine offspring, with more pronounced dysfunctions in smoking than nicotine offspring. Maternal bupropion did not impact offspring's blood pressure, endothelium-dependent relaxation, and vascular contraction. In conclusion, maternal nicotine intervention adversely affects offspring's cardiovascular outcomes, albeit less severely than continued smoking. However, bupropion causes cardiac derangement in offspring but does not adversely affect blood pressure and vascular function.

Childhood hematologic cancer and residential proximity to oil and gas development

BACKGROUND

Oil and gas development emits known hematological carcinogens, such as benzene, and increasingly occurs in residential areas. We explored whether residential proximity to oil and gas development was associated with risk for hematologic cancers using a registry-based case-control study design.

METHODS

Participants were 0-24 years old, living in rural Colorado, and diagnosed with cancer between 2001-2013. For each child in our study, we calculated inverse distance weighted (IDW) oil and gas well counts within a 16.1-kilometer radius of residence at cancer diagnosis for each year in a 10 year latency period to estimate density of oil and gas development. Logistic regression, adjusted for age, race, gender, income, and elevation was used to estimate associations across IDW well count tertiles for 87 acute lymphocytic leukemia (ALL) cases and 50 non-Hodgkin lymphoma (NHL) cases, compared to 528 controls with non-hematologic cancers.

FINDINGS

Overall, ALL cases 0-24 years old were more likely to live in the highest IDW well count tertiles compared to controls, but findings differed substantially by age. For ages 5-24, ALL cases were 4.3 times as likely to live in the highest tertile, compared to controls (95% CI: 1.1 to 16), with a monotonic increase in risk across tertiles (trend p-value = 0.035). Further adjustment for year of diagnosis increased the association. No association was found between ALL for children aged 0-4 years or NHL and IDW well counts. While our study benefited from the ability to select cases and controls from the same population, use of cancer-controls, the limited number of ALL and NHL cases, and aggregation of ages into five year ranges, may have biased our associations toward the null. In addition, absence of information on O&G well activities, meteorology, and topography likely reduced temporal and spatial specificity in IDW well counts.

CONCLUSION

Because oil and gas development has potential to expose a large population to known hematologic carcinogens, further study is clearly needed to substantiate both our positive and negative findings. Future studies should incorporate information on oil and gas development activities and production levels, as well as levels of specific pollutants of interest (e.g. benzene) near homes, schools, and day care centers; provide age-specific residential histories; compare cases to controls without cancer; and address other potential confounders, and environmental stressors.

Birth weight and risk of paediatric Hodgkin lymphoma: Findings from a population-based record linkage study in California

OBJECTIVE

To evaluate the relationship between birth weight (along with a variety of pre and perinatal characteristics) and the risk of paediatric Hodgkin lymphoma (HL) diagnosed at age <20 years.

METHOD

We linked California statewide birth records from 1978-2009 and cancer diagnosis data from 1988-2011 to conduct a population-based case-control study with 1216 cases and 4485 controls (matched on birth month and year, sex, and race/ethnicity). Conditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI) of paediatric HL overall and by age of diagnosis, controlling for other perinatal factors.

RESULTS

Compared to children with a normal birth weight (2500-3999 g), those who had a high birth weight (≥4000 g) had an increased risk of paediatric HL overall (OR = 1.23, 95% CI: 1.02-1.48) after adjusting for birth order, maternal age at the time of delivery, and paternal age at the time of delivery. The magnitude of association appeared larger for subgroups of children whose age of diagnosis was 0-10 years (OR = 1.56, 95% CI: 1.04-2.24) or 15-19 years (OR = 1.43, 95% CI: 1.11-1.83), while no association was observed in 11-14 year olds. Compared with firstborn children, those who were third or higher in birth order had a reduced risk of paediatric HL overall (OR = 0.80, 95% CI: 0.67-0.95), and this association also varied by age of diagnosis.

CONCLUSIONS

In this study with the largest number of paediatric HL cases, high birth weight was associated with an increased disease risk for most but not all ages of diagnosis. The different findings by age of diagnosis regarding both birth weight and birth order underscore the importance to stratify paediatric HL by age at diagnosis in future etiological investigations.

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.

Disparities in the Context of Opportunities for Cancer Prevention in Early Life

Persistent health disparities are a major contributor to disproportionate burden of cancer for some populations. Health disparities in cancer incidence and mortality may reflect differences in exposures to risk factors early in life. Understanding the distribution of exposures to early life risk and protective factors for cancer across different populations can shed light on opportunities to promote health equity at earlier developmental stages. Disparities may differentially influence risk for cancer during early life and create opportunities to promote health equity. Potential risk and protective factors for cancer in early life reveal patterns of disparities in their exposure. These disparities in exposures can manifest in downstream disparities in risk for cancer. These risk and protective factors include adverse childhood experiences; maternal alcohol consumption in pregnancy; childhood obesity; high or low birth weight; benzene exposure; use of assisted reproductive technologies; pesticide and insecticide exposure; isolated cryptorchidism; early pubertal timing; exposure to radiation; exposure to tobacco in utero and in early life; allergies, asthma, and atopy; and early exposure to infection. Disparities on the basis of racial and ethnic minority status, economic disadvantage, disability status, sex, geography, and nation of origin can occur in these risk and protective factors. Vulnerable populations experience disproportionally greater exposure to risk factors in early life. Addressing disparities in risk factors in early life can advance opportunities for prevention, promote health equity, and possibly reduce risk for subsequent development of cancer.

Opportunities During Early Life for Cancer Prevention: Highlights From a Series of Virtual Meetings With Experts

Compelling evidence suggests that early life exposures can affect lifetime cancer risk. In 2014, the Centers for Disease Control and Prevention's (CDC's) Cancer Prevention Across the Lifespan Workgroup hosted a series of virtual meetings with select experts to discuss the state of the evidence linking factors during the prenatal period and early childhood to subsequent risk of both pediatric and adult cancers. In this article, we present the results from a qualitative analysis of the meeting transcripts and summarize themes that emerged from our discussions with meeting participants. Themes included the state of the evidence linking early life factors to cancer risk, research gaps and challenges, the level of evidence needed to support taking public health action, and the challenges of communicating complex, and sometimes conflicting, scientific findings to the public. Opportunities for collaboration among public health agencies and other stakeholders were identified during these discussions. Potential next steps for the CDC and its partners included advancing and building upon epidemiology and surveillance work, developing and using evidence from multiple sources to inform decision-making, disseminating and communicating research findings in a clear and effective way, and expanding collaborations with grantees and other partners. As the science on early life factors and cancer risk continues to evolve, there are opportunities for collaboration to translate science into actionable public health practice.

Investigating the Effects of Exposure to Waterpipe Smoke on Pregnancy Outcomes Using an Animal Model

INTRODUCTION

In recent years, waterpipe tobacco smoking has been increasing in popularity all over the world. In this study, we explored effects of waterpipe smoking on pregnancy outcomes in rats.

METHODS

Animals were exposed to waterpipe tobacco smoking using a whole body exposure system 2 hours per day during pregnancy. A control group was exposed to fresh air only.

RESULTS

The results showed significant association between exposure to waterpipe smoke during pregnancy and low birth weight (P < .01) and neonatal death (P < .01). In addition, the rate of growth of offspring of the waterpipe group was significantly lower than that of control group as measured by body weight gain during the first 3 months of life (P < .001). No effect was found for waterpipe smoking on mean number of progeny and male to female ratio among offspring.

CONCLUSION

Waterpipe smoking is associated with adverse effects on pregnancy outcomes.

IMPLICATIONS

In this study, we investigated for the first time the effect of waterpipe smoking on pregnancy outcomes using animal model. The results clearly showed that waterpipe smoking is associated with adverse effects on pregnancy outcomes that include low birth weigh, neonatal survival, and growth retardation.

[Analysis of small areas of pediatric cancer in the municipality of Murcia (Spain)]

INTRODUCTION

Occasionally, primary care pediatricians notice the presence of small clusters of pediatric cancer (PC), but are often frustrated by the findings after statistical analysis. The study of small areas in spatial epidemiology has led to advances in identifying clusters and the environmental risk factors involved. The purpose of this study was to describe the PC incidence and the spatial distribution at the minimum level of disaggregation possible in Murcia, presenting the first urban municipality map of PC in Spain.

MATERIALS AND METHODS

A population-based descriptive study was conducted on the PC cases diagnosed in children younger than 15 years, between 1998 and 2013 in the municipality of Murcia. Cases were classified by sex, age group, and tumor type. Coordinates of home addresses at the time of diagnosis were assigned to each case, and spatial and spatio-temporal analyses were carried out at the level of census tracts, using FleXScan and SatScan.

RESULTS

A total of 155 cases of PC were diagnosed during this period. The overall incidence of PC (138/10(6) of children under the age of 15) and the incidence for individual tumor types were within the expected ranges for Europe. A spatio-temporal cluster of Hodgkin lymphoma was identified.

CONCLUSIONS

Small area analysis of PC cases may be a useful tool for the identification of PC clusters, which would allow for the generation of hypotheses regarding disease etiology, as well as developing urban models for environmental surveillance of PC.

A meta-analysis of parental smoking and the risk of childhood brain tumors

OBJECTIVE

Previous studies regarding the association between parental smoking and the risk of childhood brain tumors (CBT) have reported inconsistent results. We performed a meta-analysis to summarize evidence on this association and to quantify the potential dose-response relationship.

METHODS

A systematic literature search was conducted in the Medline and Embase databases. The summary relative risks (RRs) with 95% confidence intervals (CIs) were calculated. Dose-response meta-analysis was also performed for studies that reported categorical risk estimates for a series of smoking exposure levels.

RESULTS

A total of 17 studies fulfilled the inclusion criteria. In the meta-analyses, the summary RRs (95% CIs) of CBT for maternal smoking during pregnancy, paternal smoking during pregnancy, maternal smoking before pregnancy, and paternal smoking before pregnancy were 0.96 (0.86-1.07), 1.09 (0.97-1.22), 0.93 (0.85-1.00), and 1.09 (1.00-1.20), respectively. Dose-response meta-analysis also showed no significant association between parental smoking and the risk of CBT.

CONCLUSIONS

Findings from our meta-analysis indicate that parental smoking may not be associated with a risk of CBT.

Birth characteristics and risk of lymphoma in young children

BACKGROUND

Lymphoma is the third most common childhood malignancy and comprises two types, Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL). The etiology of pediatric lymphomas is largely unknown, but has been suggested to have prenatal origins.

METHODS

In this population-based study, California birth certificates were identified for 478 lymphoma cases diagnosed in children 0-5 years of age between 1988 and 2007; 208,015 controls frequency-matched by birth year were randomly selected from California birth records.

RESULTS

Compared to non-Hispanic whites, Hispanic children had an increased risk of HL (odds ratio (OR) and 95% confidence interval (CI) 2.43 [1.14, 5.17]), and in particular, were diagnosed more often with the mixed cellularity subtype. For all types of lymphoma, we observed an about twofold risk increase with indicators for high risk pregnancies including tocolysis, fetopelvic disproportion and previous preterm birth. NHL risk doubled with the complication premature rupture of membranes (OR and 95% CI 2.18 [1.12, 4.25]) and HL with meconium staining of amniotic fluids (OR and 95% CI 2.55 [1.01, 6.43]).

CONCLUSION

These data support previously reported associations between Hispanic ethnicity and HL and suggest that pregnancy related factors, such as intra-uterine infections and factors associated with preterm labor, may be involved in lymphoma pathogenesis.

Cancer risk in children and adolescents with birth defects: a population-based cohort study

Objective

Birth defects are an increasing health priority worldwide, and the subject of a major 2010 World Health Assembly Resolution. Excess cancer risk may be an added burden in this vulnerable group of children, but studies to date have provided inconsistent findings. This study assessed the risk for cancer in children and young adolescents with major birth defects.

Methods and Findings

This retrospective, statewide, population-based, cohort study was conducted in three US states (Utah, Arizona, Iowa). A cohort of 44,151 children and young adolescents (0 through 14 years of age) with selected major, non-chromosomal birth defects or chromosomal anomalies was compared to a reference cohort of 147,940 children without birth defects randomly sampled from each state’s births and frequency matched by year of birth. The primary outcome was rate of cancer prior to age 15 years, by type of cancer and type of birth defect. The incidence of cancer was increased 2.9-fold (95% CI, 2.3 to 3.7) in children with birth defects (123 cases of cancer) compared to the reference cohort; the incidence rates were 33.8 and 11.7 per 100,000 person-years, respectively. However, the excess risk varied markedly by type of birth defect. Increased risks were seen in children with microcephaly, cleft palate, and selected eye, cardiac, and renal defects. Cancer risk was not increased with many common birth defects, including hypospadias, cleft lip with or without cleft palate, or hydrocephalus.

Conclusion

Children with some structural, non-chromosomal birth defects, but not others, have a moderately increased risk for childhood cancer. Information on such selective risk can promote more effective clinical evaluation, counseling, and research.

Prenatal exposure to cigarette smoke alters later-life antitumor cytotoxic T-lymphocyte (CTL) activity via possible changes in T-regulatory cells

Epidemiological studies suggest that maternal smoking increases the incidence in the progeny of certain childhood cancers. Our previous study in mice demonstrated the feasibility of such an association by demonstrating that prenatal exposure to cigarette smoke (CS) elevated the incidence of transplanted tumors and reduced cytotoxic T-lymphocyte (CTL) activity in juvenile male offspring. The current study extends these findings by investigating the relationship between CS-induced CTL suppression and effects on regulators of effector T-cell activity, such as T-regulatory (Treg; CD4+ CD25+ Foxp3+) cells and transforming growth factor (TGF)-β. Results here demonstrate that in utero exposure to CS, at a maternal particle concentration of 15 mg/m3 (4 h/d, 5 d/wk), significantly reduced ex vivo CTL activity of whole splenocytes (and isolated CD8+ cells) against tumor cells both before and after injection of prenatally exposed mice with EL4 lymphoma cells. In contrast, prenatal CS exposure significantly increased levels of thymic Treg cells in a time-dependent manner following tumor cell injection. In vitro production of TGF-β by splenocytes recovered from prenatally exposed, tumor-bearing mice was also altered. Neither prenatal CS exposure nor subsequent administration of EL4 cells exerted any marked effects on lymphoid organ weights, cellularity, or histologic profiles. Given that Treg cells and TGF-β suppress effector T-cell activities, these findings suggest possible immune mechanisms by which early exposure to CS reduces CTL tumoricidal activity during tumor cell development. Data suggest that children of smoking mothers may be less able to mount an appropriate adaptive immune response to tumors, thus increasing their risk for some cancers later in life.

Obesity and risk of malignant melanoma: a meta-analysis of cohort and case-control studies

Although obesity is an established risk factor for several cancer types, its possible role in the aetiology of malignant melanoma remains unclear. This meta-analysis aims to examine the association between obesity and melanoma risk, exploring any tentative gender-specific associations. After the identification of eligible studies, we estimated pooled effect estimates (odds ratios and relative risks), undertook a meta-regression analysis and analysed separately risk of malignant melanoma among males and females in relation to body mass index (BMI) and body surface area (BSA). Out of the 21 eligible articles, 11 used a case-control design encompassing 4460 cases/6342 controls; 10 used a cohort design whose total size comprised 7895 incident cases/6,368,671 subjects. Among males, the pooled effect estimate was 1.31 (95%confidence interval (CI): 1.18-1.45) for overweight and 1.31 (95%CI: 1.19-1.44) for obese. Meta-regression revealed no significant slope, most probably due to the underlying plateau in effect estimates. Among females, no significant association was documented; the pooled effect estimate for overweight and obese subjects was 0.98 (95%CI: 0.92-1.05) and 0.99 (95%CI: 0.83-1.18), respectively. Noticeably, there was evidence for confounding between sunlight exposure and obesity in females. All results were reproducible upon analyses on BSA. In conclusion, overweight and obesity are associated with increased risk of malignant melanoma among males. Meticulous assessment of sunlight exposure is needed especially in women, since self limited public sun exposure may be prevalent among overweight or obese females. Higher-order associations between BMI and melanoma risk should be addressed and examined by the future studies.

Allergy-associated symptoms in relation to childhood non-Hodgkin's as contrasted to Hodgkin's lymphomas: a case-control study in Greece and meta-analysis

An increase of the prevalence of childhood allergic diseases and the incidence of childhood Hodgkin's (HL) and non-Hodgkin's lymphoma (NHL) were reported in the late 20th century. Among adults, several studies point to an inverse association with lymphoma; it remains to be confirmed whether allergy is also related to childhood lymphomas and whether the association, if any, is of an aetiologic nature. Between 1996 and 2008, 277 children (aged 0-14 years) with HL (N = 111) or NHL (N = 166) were enrolled in Nationwide Registry for Childhood Hematological Malignancies (NARECHEM), a Greek hospital-based-registry of childhood hematological malignancies. Hospital controls were individually matched to cases on age and sex. Multivariate conditional logistic regression was used to estimate odds ratios (ORs) with 95%confidence intervals (CIs) for associations of allergic diseases and other covariates with childhood HL or NHL risk. Subsequently, we combined our results with those of a French case-control study in a meta-analysis amounting to a total of 330 NHL cases/1478 controls and 239 HL cases/959 controls. After controlling for sociodemographic, perinatal and environmental factors, childhood NHL was less prevalent among children with allergy-associated symptoms overall (OR:0.50, 95%CI:0.27-0.92) or a history of asthma (OR:0.43, 95%CI:0.21-0.88). By contrast, allergy did not seem to be associated with childhood HL risk, although statistical power was limited. Fewer seaside holidays and higher birth weight were also associated with increased childhood NHL risk. The combined OR of the two studies for the association of asthma with NHL risk was: 0.52, 95%CI:0.32-0.84, whereas for HL: 0.86, 95%CI:0.51-1.45. Allergy seems to be strongly and inversely associated with childhood NHL. It remains to be elucidated in future investigations comprising larger populations, focusing on specific disease subtypes and employing more pertinent study-designs, whether this association is genuinely protective.

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.

Is birth weight associated with childhood lymphoma? A meta-analysis

Several risk factors have been identified for childhood lymphomas. The purpose of this meta-analysis was to synthesize current evidence regarding the association between birth weight with primarily the risk for non-Hodgkin lymphoma (NHL), given its similarity to acute lymphoblastic leukemia, Hodgkin lymphoma (HL) and any category of lymphoma. Two cohort (278,751 children) and seven case-control studies (2,660 cases and 69,274 controls) were included. Effects estimates regarding NHL, HL and any lymphoma were appropriately pooled using fixed or random effects model in two separate analyses: specifically, high was compared to normal or any birth weight. Similarly, low was compared to normal or any birth weight. No statistically significant association was found between high birth weight, as compared to normal birth weight, and risk for NHL plus Burkitt lymphoma (OR = 1.17, 95% CI = 0.76-1.80, random effects), HL (OR = 0.94, 95% CI = 0.64-1.38, fixed effects) or any plus Burkitt lymphoma (OR = 1.09, 95% CI = 0.76-1.56, fixed effects). A null association emerged when low was compared with normal birth weight for NHL plus Burkitt lymphoma (OR = 1.07, 95% CI = 0.71-1.62, random effects), HL (OR = 0.94, 95% CI = 0.54-1.65, fixed effects) or any plus Burkitt lymphoma (OR = 1.02, 95% CI = 0.79-1.33, fixed effects). Accordingly, no association was found when high or low birth weight was compared to any birth weight. Although current evidence suggests no association, birth weight might be a too crude indicator to reveal a genuine association of fetal growth with specific lymphoma categories; hence, there is an emerging need for use of more elaborate proxies, at least those accounting for gestational week.