Birth characteristics, maternal reproductive history, and the risk of infant leukemia: a report from the Children's Oncology Group

Maternal Body Mass Index, Gestational Weight Gain, and Risk of Cancer in Offspring: A Systematic Review and Meta-Analysis

Background: Mounting evidence suggests that maternal obesity and gestational weight gain (GWG) may increase the risk of cancer in their offspring; however, results are inconsistent. The purpose of this research is to determine the association between maternal body mass index (BMI) and GWG and the risk of cancer in offspring through a systematic and comprehensive meta-analysis. Methods: A systematic literature search of several databases was conducted on 1 October 2022 to identify relevant studies. The quality of the included studies was evaluated using the Newcastle–Ottawa scale. The overall risk estimates were pooled using a random-effects meta-analysis. Results: Twenty-two studies with more than 8 million participants were included. An increased risk of total cancer was found in offspring whose mothers had a high GWG (odds ratio [OR]: 1.10; 95% CI: 1.01–1.19; p: 0.040) but not in offspring whose mothers had a low GWG (OR: 1.06; 95% CI: 0.96–1.17; p: 0.030), when compared with offspring whose mothers had a suitable GWG. In addition, no statistically significant association was found between maternal underweight (OR: 1.05; 95% CI: 0.97–1.13; p: 0.630), overweight/obesity (OR: 1.07; 95% CI: 0.99–1.16; p: 0.020), and risk of total cancer in offspring. Conclusions: Our study proposes evidence that maternal BMI and GWG may be associated with the risk of cancer in offspring, although statistical significance was found only for high GWG. Further well-designed research is required to clarify the potential relevance of maternal BMI and GWG on offspring cancer, especially for specific cancers.

Maternal obesity and acute lymphoblastic leukemia risk in offspring: A summary of trends, epidemiological evidence, and possible biological mechanisms

Acute lymphoblastic leukemia, a heterogenous malignancy characterized by uncontrolled proliferation of lymphoid progenitors and generally initiated in utero, is the most common pediatric cancer. Although incidence of ALL has been steadily increasing in recent decades, no clear reason for this trend has been identified. Rising concurrently with ALL incidence, increasing maternal obesity rates may be partially contributing to increasing ALL prevelance. Epidemiological studies, including a recent meta-analysis, have found an association between maternal obesity and leukemogenesis in offspring, although mechanisms underlying this association remain unknown. Therefore, the purpose of this review is to propose possible mechanisms connecting maternal obesity to ALL risk in offspring, including changes to fetal/neonatal epigenetics, altered insulin-like growth factor profiles and insulin resistance, modified adipokine production and secretion, changes to immune cell populations, and impacts on birthweight and childhood obesity/adiposity. We describe how each proposed mechanism is biologically plausible due to their connection with maternal obesity, presence in neonatal and/or fetal tissue, observation in pediatric ALL patients at diagnosis, and association with leukemogenesis, A description of ALL and maternal obesity trends, a summary of epidemiological evidence, a discussion of the pathway from intrauterine environment to subsequent malignancy, and propositions for future directions are also presented.

Maternal BMI, Diabetes, and Gestational Weight Gain and Risk for Pediatric Cancer in Offspring: A Systematic Review and Meta-Analysis

Background

Pediatric cancer incidence has steadily increased concurrent with rising adult obesity, but associations between maternal obesity and associated comorbidities and pediatric cancer risk remain understudied. We aimed to quantitatively characterize associations of pediatric cancer risk with maternal prepregnancy body mass index (BMI), gestational weight gain, and maternal diabetes.

Methods

We performed a comprehensive and systematic literature search in Ovid and EMBASE from their inception to March 15, 2021. Eligible studies reported risk estimates and sample sizes and provided sufficient description of outcome and exposure ascertainment. Random effects models were used to estimate pooled effects.

Results

Thirty-four studies were included in the analysis. Prepregnancy BMI was positively associated with leukemia risk in offspring (odds ratio [OR] per 5-unit BMI increase =1.07, 95% confidence intervals [CI] = 1.04 to 1.11; I² = 0.0%). Any maternal diabetes was positively associated with acute lymphoblastic leukemia risk (OR = 1.46, 95% CI = 1.28 to 1.67; I² = 0.0%), even after restricting to birthweight-adjusted analyses (OR = 1.74, 95% CI = 1.29 to 2.34; I² = 0.0%), and inversely associated with risk of central nervous system tumors (OR = 0.73, 95% CI = 0.55 to 0.97; I² = 0.0%). Pregestational diabetes (OR = 1.57, 95% CI = 1.11 to 2.24; I² = 26.8%) and gestational diabetes (OR = 1.40, 95% CI = 1.12 to 1.75; I² = 0.0%) were also positively associated with acute lymphoblastic leukemia risk. No statistically significant associations were observed for gestational weight gain.

Conclusions

Maternal obesity and diabetes may be etiologically linked to pediatric cancer, particularly leukemia and central nervous system tumors. Our findings support weight management and glycemic control as important components of maternal and offspring health. Further validation is warranted.

Caesarean sections, prenatal and postnatal conditions and childhood acute lymphoblastic leukaemia: A case-control study in the State of São Paulo, Brazil

INTRODUCTION

Brazil has high rates of caesarean sections, which has been suggested as a risk factor for acute lymphoblastic leukaemia (ALL). In addition, some pre- and postnatal conditions have been identified as relevant in the etiology of ALL.

OBJECTIVES

Investigate the association of caesarean sections, pre- and postnatal conditions with childhood ALL in the State of São Paulo.

METHODS

Population-based case-control study including children that are below10 years old. Information on study variables was obtained through face to face interviews, through a questionnaire, and the State of São Paulo Declarations of Live Births database. The conditional and unconditional logistic regression approaches were used to calculate the odds ratio (OR) of the associations between caesarean sections, pre- and postnatal conditions with ALL, and 95 % confidence intervals (95 % CI).

RESULTS

We observed a weak and non-statistically significant risk for ALL among children exposed to caesarean sections (unconditional logistic regression OR 1.08; 95 % CI 0.70-1.66; conditional logistic regression OR 1.21; 95 % CI 0.72-2.02), but among children under 3 years old and born through a caesarean sections, the risk of ALL was greater (unconditional logistic regression OR 1.70; 95 % CI 0.69-4.21). A negative association for ALL was observed among children with mothers who reported 12 years of schooling or more (unconditional logistic regression OR 0.34; 95 % CI 0.16-0.69).

CONCLUSIONS

We found a tenuous suggestive association between caesarean sections and childhood ALL. The mother's high level of education showed an inverse association with ALL.

Pre-pregnancy obesity and childhood malignancies: A population-based cohort study

OBJECTIVE

Exploring the effect of maternal obesity during pregnancy on the long-term health of offspring is of great importance. The aim of this study was to evaluate the association between maternal pre-pregnancy obesity and future risk of childhood malignancies.

STUDY DESIGN

A population-based cohort analysis comparing the risk for long-term childhood malignancies (up to the age of 18 years) in children born (1991-2014) to mothers with and without pre-pregnancy obesity (body mass index > 30) was conducted in July 2017. Childhood malignancies were predefined based on ICD-9 codes, as recorded in the hospital medical files. Children with congenital malformations and multiple gestations were excluded from the analysis. The Kaplan-Meier survival curve was constructed to compare cumulative oncological morbidity in both groups over time. The Cox proportional hazards model was used to control for confounders.

RESULTS

During the study period, 241 273 infants met the inclusion criteria; 3268 were born to mothers with pre-pregnancy obesity. Children of obese women had significantly increased risk for several childhood malignancies (including brain tumors) as well as increased risk for total hospitalizations with malignancy diagnoses, even after controlling for several confounders (adjusted HR 1.90, 95% CI 1.07-3.37, P = 0.028). Cumulative incidence of oncological morbidity was also significantly increased over time in the studied group (log-rank P = 0.023).

CONCLUSION

Maternal pre-pregnancy obesity is significantly associated with an increased long-term risk for general childhood malignancies, and specifically brain tumors in the offspring. These results are important when counseling mothers regarding potential future risks and recommended lifestyle modifications.

Main Nutritional and Environmental Risk Factors in Children with Leukemia from a Public Hospital of the State of Guanajuato, Mexico

Introduction::

The prevalence of leukemia in children aged under 19 years continues to increase. Nutritional and environmental factors have been described as causes of their development, and maternal breastfeeding, birth weight, exposure to cow’s milk or to contaminants before 1 year of age, and smoking have been studied.

Objective::

To analyze the main nutritional and environmental risk factors in children with Acute Lymphoblastic Leukemia (ALL) in a public hospital in Guanajuato, Mexico.

Methods::

Analytical and cross-sectional study on 30 children under 18 years of age, with a confirmed diagnosis of ALL in a public hospital in Guanajuato, Mexico. With the signed informed consent of the children’s parents, a questionnaire was applied that collected and in which nutritional risk factors (weeks of gestation and birth weight, breastfeeding, exposure to cow’s milk) and environmental factors (smoking and exposure to arsenic) were evaluated. The frequencies and Odds Ratios (OR) of the main nutritional and environmental risk factors were obtained.

Results::

Mean age was 8 ± 4 years with 38 ± 1 weeks of gestation, with a birth weight of 3,200 g (range, 2,500-4,800 g). Fifty percent of the children consumed cow’s milk during their first year of life (40% before 6 months of age); 33.3% received maternal milk for ≤6 months and 63% of the parents had a positive smoking habit, with 66.6% of the participants living in cities with arsenic levels falling outside of the norm.

Conclusion::

The main nutritional and environmental risk factors found were early complementary feeding, cow’s milk prior to 1 year of age, a duration of breastfeeding of fewer than 6 months, birth weight of >3,500 g, a positive smoking habit in the children’s parents, as well as exposure to arsenic in drinking water. Identification of these risk factors could constitute an input for integrating novel prevention alternatives and the nutritional management of leukemia.

Maternal Obesity, Birth Size, and Risk of Childhood Cancer Development

Infants and children are particularly vulnerable to in utero and early-life exposures. Thus, a mother's exposures before and during pregnancy could have important consequences for her child's health, including cancer development. We examined whether birth certificate-derived maternal anthropometric characteristics were associated with increased risk of subsequent childhood cancer development, accounting for established maternal and infant risk factors. Pennsylvania birth and cancer registry files were linked by the state Department of Health, yielding a virtual cohort of births and childhood cancers from 2003 through 2016. The analysis included 1,827,875 infants (13,785,309 person-years at risk), with 2,352 children diagnosed with any cancer and 747 with leukemia before age 14 years. Children born to mothers with a body mass index (weight (kg)/height (m)2) of ≥40 had a 57% (95% confidence interval: 12, 120) higher leukemia risk. Newborn size of ≥30% higher than expected was associated with 2.2-fold and 1.8-fold hazard ratios for total childhood cancer and leukemia, respectively, relative to those with expected size. Being <30% below expected size also increased the overall cancer risk (P for curvilinearity < 0.0001). Newborn size did not mediate the association between maternal obesity and childhood cancer. The results suggest a significant role of early-life exposure to maternal obesity- and fetal growth-related factors in childhood cancer development.

Mother and child characteristics at birth and early age leukemia: a case-cohort population-based study

OBJECTIVE

The population-based cancer registries (PBCR) and the Information System on Live Births in Brazil (Sistema de Informações sobre Nascidos Vivos [SINASC]) have information that enables the test for risk factors associated with leukemia at an early age. The aim of this study was to identify maternal and birth characteristics associated with early-age acute leukemia (EAL) in Brazil.

METHODS

A case-cohort study was performed using secondary dataset information of PBCR and SINASC. The risk association variables were grouped into (i) characteristics of the child at birth and (ii) characteristics of maternal exposure during pregnancy. The case-control ratio was 1:4. Linkage was performed using R software; odds ratio (OR) and 95% confidence interval (CI) were calculated by logistic regression models.

RESULTS

EAL was associated with maternal occupational exposure to chemicals (agricultural, chemical, and petrochemical industry; adjOR: 2.18, 95% CI: 1.16-4.10) and with birth defects (adjOR: 3.62, 95% CI: 1.19-11.00).

CONCLUSIONS

The results of this study, with the identification of EAL risk factors in population-based case-cohort study, strengthen the knowledge and improve databases, contributing to investigations on risk factors associated with childhood leukemia worldwide.

Parental Age and Risk of Infant Leukaemia: A Pooled Analysis

BACKGROUND

Infant leukaemia (IL) is extremely rare with fewer than 150 cases occurring each year in the United States. Little is known about its causes. However, recent evidence supports a role of de novo mutations in IL aetiology. Parental age has been associated with several adverse outcomes in offspring, including childhood cancers. Given the role of older parental age in de novo mutations in offspring, we carried out an analysis of parental age and IL.

METHODS

We evaluated the relationship between parental age and IL in a case-control study using registry data from New York, Minnesota, California, Texas, and Washington. Records from 402 cases [219 acute lymphoblastic leukaemia (ALL), 131 acute myeloid leukaemia (AML), and 52 other] and 45 392 controls born during 1981-2004 were analysed. Odds ratios (OR) and 95% confidence intervals (CI) were calculated by logistic regression. Estimates were adjusted for infant sex, birth year category, maternal race, state, and mutually adjusted for paternal or maternal age, respectively.

RESULTS

Infants with mothers' age ≥40 years had an increased risk of developing AML (OR 4.80, 95% CI 1.80, 12.76). In contrast, paternal age <20 was associated with increased risk of ALL (OR 3.69, 95% CI 1.62, 8.41).

CONCLUSION

This study demonstrates increased risk of infant ALL in relation to young paternal age. Given record linkage, there is little concern with recall or selection bias, although data are lacking on MLL gene status and other potentially important variables. Parent of origin effects, de novo mutations, and/or carcinogenic exposures may be involved in IL aetiology.

Maternal pre-pregnancy and gestational diabetes, obesity, gestational weight gain, and risk of cancer in young children: a population-based study in California

PURPOSE

We aimed to examine the influence of pre-pregnancy diabetes, pre-pregnancy body mass index (BMI), gestational diabetes, and gestational weight gain on childhood cancer risk in offspring.

METHODS

We identified cancer cases (n = 11,149) younger than age 6 years at diagnosis from the California Cancer Registry registered between 1988 and 2013. Controls (n = 270,147) were randomly sampled from California birth records, and frequency matched by year of birth to all childhood cancers during the study period. Exposure and covariate information were extracted from birth records. Unconditional logistic regression models were generated to assess the importance of pre-pregnancy diabetes, pre-pregnancy BMI, gestational diabetes, and gestational weight gain on childhood cancer risk.

RESULTS

We observed increased risks of acute lymphoblastic leukemia and Wilms' tumor in children of mothers with pre-pregnancy diabetes [odds ratio (OR) 95 % confidence interval (CI) 1.37 (1.11, 1.69); OR (95 % CI) 1.45 (0.97, 2.18), respectively]. When born to mothers who were overweight prior to pregnancy (BMI 25-<30), children were at increased risk of leukemia [OR (95 % CI) 1.27 (1.01, 1.59)]. Insufficient gestational weight gain increased the risk of acute myeloid leukemia [OR (95 % CI) 1.50 (0.92, 2.42)] while excessive gestational weight gain increased the risk of astrocytomas [OR (95 % CI) 1.56 (0.97, 2.50)]. No associations were found between gestational diabetes and childhood cancer risk in offspring.

CONCLUSIONS

We estimated elevated risks of several childhood cancers in the offspring of mothers who had diabetes and were overweight prior to pregnancy, as well as mothers who gained insufficient or excessive weight. Since few studies have focused on these factors in relation to childhood cancer, replication of our findings in future studies is warranted.

Estradiol induces gene proximity and MLL-MLLT3 fusion in an activation-induced cytidine deaminase-mediated pathway

Epidemiological data have linked birth control formulations to an increased risk of infant acute leukemia involving MLL rearrangements. Reverse transcription polymerase chain reaction (RT-PCR) studies showed that 10 nM estradiol enhanced MLL transcription in addition to its common translocation partners, MLLT2 (AF4) and MLLT3 (AF9). The same concentration of estradiol triggered MLL and MLLT3 co-localization without affecting the interaction of genes located on the same chromosomes. Estradiol also stimulated the generation of MLL-MLLT3 fusion transcripts as seen by RT-PCR. RNAi knockdown of activation-induced cytidine deaminase (AICDA) suppressed the induction of MLL-MLLT3 fusion transcript formation observed with estradiol. Additionally, chromatin immunoprecipitation (ChIP) analysis showed estradiol dependent localization of AICDA in MLL intron 11, upstream of a hotspot for both DNA cleavage and rearrangement, but not downstream within intron 12. Combined, these studies show that levels of estradiol consistent with that observed during pregnancy have the potential to initiate MLL fusions through an AICDA-mediated mechanism.

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.

Parental age, family size, and offspring's risk of childhood and adult acute leukemia

BACKGROUND

An association between childhood acute leukemia and advanced parental age was observed more than 50 years ago, and the association has been repeated in several, but not all, subsequent studies. In contrast to the many studies addressing childhood leukemia, few have included adult patients.

METHODS

In this register-based case-control study, we examined the association between parental age and incidence of acute leukemia in 2,660 childhood cases and 4,412 adult cases of acute leukemia, compared with 28,288 age-matched controls selected from a population-based register. Relative risks were estimated with conditional logistic regression.

RESULTS

We found a small increased risk of childhood acute lymphoblastic leukemia with increasing paternal age (adjusted OR, 1.05 per 5-year increase in age). Risk estimates were similar for childhood acute myeloid leukemia (AML), whereas no association was found with adult leukemia. Meanwhile, we observed a decreased risk of adult AML with increasing number of siblings, both older and younger.

CONCLUSIONS

The results support the idea of a prenatal etiology of leukemia but indicate that parental age effects are limited to childhood cases.

IMPACT

This is the first large study on parental age and leukemia risk, which includes adult cases. The finding on family size and risk of adult AML needs to be validated in future studies.

Immunophenotype and cytogenetic characteristics in the relationship between birth weight and childhood leukemia

BACKGROUND

High birth weight increases the risk of childhood acute lymphoid leukemia (ALL) through unknown mechanisms. Whether this risk is specific to ALL subtypes is unknown, and low case numbers have prevented investigation of the rarer leukemias. Here we address these associations using a large population-based dataset.

PROCEDURE

Using the National Registry of Childhood Tumors, birth weights of 7,826 leukemia cases, defined by immunophenotype and cytogenetic subgroup, were compared with those of 10,785 controls born in England and Wales between 1980 and 2007.

RESULTS

The risk for overall leukemia increases 7% with each 0.5 kg increase in birth weight (OR 1.07, 95%CI 1.04-1.10). This risk is limited to the lymphoid leukemias (OR 1.08, 95%CI 1.05-1.12) diagnosed between 1 and 9 years of age. Analysis by cytogenetic feature reveals that there appears to be association with specific chromosomal abnormality: the risk of tumors with high hyperdiploid karyotypes increases 12% per 0.5 kg increase in birth weight (OR 1.12, 95%CI 1.05-1.20), and t(1;19) tumors show an increased risk of 41% per 0.5 kg increase (OR 1.41, 95%CI 1.09-1.84). The risk of acute myeloid leukemia is elevated in high and low birth weight babies. There is no significant risk relationship to other leukemias or myeloproliferative diseases.

CONCLUSIONS

Birth weight is a risk factor for ALL and AML. Other subtypes of the disease are not significantly affected. There appears to be association with specific chromosomal abnormality, which may aid our understanding of the development of childhood leukemia in utero.

Childhood cancer mortality and birth characteristics in Korea: a national population-based birth cohort study

To examine the relationship between birth characteristics and childhood cancer mortality, a retrospective cohort study of Korean children was conducted using data collected by the national birth register between 1995 and 2006, which were then individually linked to death data. A cohort of 6,479,406 children was followed from birth until their death or until December 31, 2006. Poisson regression analyses were used to calculate rate ratios of childhood cancer deaths according to birth characteristics. A total of 1,469 cancer deaths were noted and the childhood cancer mortality rate was found to be 3.43 per 100,000 person-years in Korea during the period of 1995-2006. The birth characteristics examined in this study (i.e. , birth weight, gestational age, multiple births, parental ages, and number of siblings) were generally found to be not significantly associated with childhood cancer mortality, and the associations did not vary meaningfully with gender nor with cancer sites. However, among children aged 5-11 yr, higher birth weight was associated with elevated childhood cancer mortality (rate ratio = 1.28, 95% confidence interval 1.04-1.58). Our results offer no overall associations between childhood cancer mortality and birth characteristics, but suggest that the association may be specific to age group.

Infant leukemia and congenital abnormalities: a Children's Oncology Group study

BACKGROUND

Leukemia in infants is rare and has not been well studied apart from leukemia in older children. Differences in survival and the molecular characteristics of leukemia in infants versus older children suggest a distinct etiology, likely involving prenatal factors.

PROCEDURE

We examined the association between eight categories of maternally reported congenital abnormalities (CAs) (cleft lip or palate, spina bifida or other spinal defect, large or multiple birthmarks, other chromosomal abnormalities, small head or microcephaly, rib abnormalities, urogenital abnormalities, and other) and infant leukemia in a case-control study. The study included 443 cases diagnosed at <1 year of age at a Children's Oncology Group Institution in the United States or Canada from 1996 to 2006 and 324 controls. Controls were recruited from the cases' geographic area either by random digit dialing (1999-2002) or through birth certificates (2003-2008) and were frequency-matched to cases on birth year. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by unconditional logistic regression after adjustment for birth year and a measure of follow-up time to account for differences in the CA observation period.

RESULTS

No statistically significant associations were observed between infant leukemia and any CA (OR = 1.2; 95% CI: 0.8-1.9), birthmarks (OR = 1.4; 95% CI: 0.7-2.5), urogenital abnormalities (OR = 0.7; 95% CI: 0.2-2.0), or other CA (OR = 1.4; 95% CI: 0.7-2.8). Results were similar for acute lymphoblastic and myeloid leukemia cases. Fewer than five subjects were in the remaining CA categories precluding analysis.

CONCLUSIONS

Overall, we did not find evidence to support an association between CAs and infant leukemia.

Genetic rearrangement MLL/AF4 is most frequent in children with acute lymphoblastic leukemias in Mexico City

One of the highest incidences of acute lymphoblastic leukemia (ALL) in the world has been reported in Mexico City. In the current study (26 cases), the frequencies of the most frequent genetic rearrangements TEL-AML1, MLL/AF4, BCR-ABL (major and minor) in ALL in children from Mexico City were determined. For the ALL, the frequency of MLL/AF4 was 65.4%, for TEL-AML1 and that of BCR/ABL was 3.8%. Only 6 of the 17 children with the MLL/AF4 rearrangement were less than 26 months old. The frequency reported for MLL/AF4 in Mexican children with ALL is one of the highest worldwide. These findings could potentially explain the higher frequency of ALL with poor prognosis for children in Mexico City.

Estrogen treatment induces MLL aberrations in human lymphoblastoid cells

Epidemiological data indicates increased risk of infant acute leukemia involving MLL gene aberrations with use of oral contraceptives. To determine whether estrogens might be implicated, we examined the effect of estradiol (E2) or 4-OH-E2 in an in vitro model of translocation susceptibility. Genomic DNA from the TK6 human lymphoblastoid cell line was screened by ligation mediated PCR and inverse PCR at a rearrangement hot spot within the MLL breakpoint cluster region to detect DNA aberrations. An increase in DNA double strand breaks was observed within this region after exposure to either E2 or 4-OH-E2. An increase in the frequency of MLL translocations was only found after exposure to E2. Induction of cleavage due to increased activation of apoptotic nucleases was excluded by pre-treatment with the pan-caspase inhibitor, zVAD.fmk. We conclude that concentrations of E2 and 4-OH-E2 that may occur during pregnancy, or during use of oral contraceptives, can cause aberrations of the MLL gene and could thus be a factor in the early events of leukemogenesis occurring in utero.

Very high birth weight of offspring is associated with an increased risk of leukemia in their mothers: results of a population-based cohort study

Although the association between birth weight and childhood leukemia is well described, the relation between a child's birth weight and parental risk of leukemia is unknown. We linked data from the Jerusalem Perinatal Study to the Israel Cancer Registry to ascertain the incidence of leukemia in mothers and fathers in relation to their offspring's birth weight. Birth weight >or=4500 g in any of the offspring was associated with a >3-fold risk of leukemia in mothers, but not fathers. Potential mechanisms include shared exposures of high birth weight infants and their mothers, possibly to radiation or growth factors, or genetic pathways leading to both high birth weight and leukemia.

Childhood cancer epidemiology in low-income countries

Global studies of childhood cancer provide clues to cancer etiology, facilitate prevention and early diagnosis, identify biologic differences, improve survival rates in low-income countries (LIC) by facilitating quality improvement initiatives, and improve outcomes in high-income countries (HIC) through studies of tumor biology and collaborative clinical trials. Incidence rates of cancer differ between various ethnic groups within a single country and between various countries with similar ethnic compositions. Such differences may be the result of genetic predisposition, early or delayed exposure to infectious diseases, and other environmental factors. The reported incidence of childhood leukemia is lower in LIC than in more prosperous countries. Registration of childhood leukemia requires recognition of symptoms, rapid access to primary and tertiary medical care (a pediatric cancer unit), a correct diagnosis, and a data management infrastructure. In LIC, where these services are lacking, some children with leukemia may die before diagnosis and registration. In this environment, epidemiologic studies would seem to be an unaffordable luxury, but in reality represent a key element for progress. Hospital-based registries are both feasible and essential in LIC, and can be developed using available training programs for data managers and the free online Pediatric Oncology Networked Data Base (www.POND4kids.org), which allows collection, analysis, and sharing of data.

High birth weight as an important risk factor for infant leukemia

In this paper, we compared the birth weight distribution among 201 infant leukaemia (IL) cases with that of 440 noncancer controls enrolled in Brazil in 1999–2005. Compared with the general population and the stratum 2500–2999 g as reference, IL cases weighing 3000–3999 g presented an odds ratio (OR) of 1.68 (95% CI: 1.03–2.76), and those of 4000 g or more, an OR of 2.28 (95% CI: 1.08–4.75), P_trend<0.01. Using hospital-based controls, the OR for 4000 g or more, compared to 2500–2999 g, was 1.30 (95% CI: 1.02–1.43) after adjusting for confounders (gender, income, maternal age, pesticide and hormonal exposure during pregnancy). The results suggest that high birth weight is associated with increased risk of IL.

Reproductive history, infertility treatment, and the risk of acute leukemia in children with down syndrome: a report from the Children's Oncology Group

BACKGROUND

Children with Down syndrome (DS) have from 10 to 20 times the risk of developing acute leukemia than the general pediatric population. There is mixed evidence for associations between reproductive history or infertility and acute leukemia among children without DS.

METHODS

The authors conducted a case-control study of acute leukemia among children with DS to investigate possible risk factors in this population. From 1997 to 2002, 158 children aged <20 years with DS who had a diagnosis of acute leukemia (97 children with acute lymphoblastic leukemia [ALL] and 61 children with acute myeloid leukemia [AML]) were enrolled at Children's Oncology Group (COG) institutions. Controls with DS (n = 173) were selected from the cases' primary care clinic and frequency matched to cases on age. Telephone interviews were conducted with mothers of cases and controls assessing reproductive history, infertility, and infertility treatment.

RESULTS

Null results were observed overall and by subtype for reproductive factors, including previous pregnancy outcomes and contraceptive use, and for most infertility outcomes. There was an increased risk of AML among children with DS whose parents had ever tried for >/=1 year to become pregnant (odds ratio [OR], 2.22; 95% confidence interval [95% CI], 1.14-4.33). A 1-year increase in maternal age also was associated with AML (OR, 1.06; 95% CI, 1.01-1.12).

CONCLUSIONS

Although the questionnaire was limited in this area, the results suggested that the risk for AML may be raised in children with DS because of infertility. In that the risk of infertility, along with having a child with DS, increase with age, these results warrant more research.