Use of medication during pregnancy and risk of childhood leukemia (Canada)

Prevention and Health Benefits of Prebiotics, Probiotics and Postbiotics in Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is the most common type of leukemia in children, comprising 75-85% of cases. Aggressive treatment of leukemias includes chemotherapy and antibiotics that often disrupt the host microbiota. Additionally, the gut microbiota may play a role in the development and progression of acute leukemia. Prebiotics, probiotics, and postbiotics are considered beneficial to health. The role of prebiotics in the treatment and development of leukemia is not well understood, but inulin can be potentially used in the treatment of leukemia. Some probiotic bacteria such as Lactobacillus shows anticancer activity in in vitro studies. Additionally, Bifidobacterium spp., as a consequence of the inhibition of growth factor signaling and mitochondrial-mediated apoptosis, decrease the proliferation of cancer cells. Many bacterial metabolites have promising anticancer potential. The available research results are promising. However, more research is needed in humans, especially in the child population, to fully understand the relationship between the gut microbiota and acute leukemia.

Danish Population Based Study of Familial Epilepsy and Childhood Cancer

Objective

Results from studies investigating the association between maternal or child epilepsy, use of anticonvulsants in pregnancy, and childhood cancer are inconsistent and at times contradictory.

Methods

Linking Danish national databases, we obtained epilepsy and childhood cancer diagnoses, and anticonvulsant use data. We estimated adjusted odds ratios of all or specific childhood cancers in relation to maternal or child epilepsy and anticonvulsant therapies using conditional logistic regression.

Results

Maternal epilepsy was positively associated with all childhood cancers in offspring, specifically, with acute lymphoblastic leukemia (Odds Ratio (OR) = 1.68, 95% Confidence Interval (CI) = 1.16, 2.43) and Wilms tumor (OR = 2.13, 95%CI = 0.97, 4.68). When considering maternal ever (lifetime) ingestion of anticonvulsants, a positive association was found with all cancers (OR = 1.15, 95%CI = 1.01, 1.31), and central nervous system tumors (OR = 1.32, 95%CI = 1.03, 1.69) as well as neuroblastoma (OR = 2.05, 95%CI = 1.29, 3.28) among offspring. Maternal anticonvulsant use before or during the index pregnancy was related to CNS tumors in offspring (OR = 1.78, 95%CI = 0.99, 3.21), however the confidence interval included the null.

Significance

Maternal use of certain anticonvulsant medications may be a risk factor for cancer in offspring. Medical providers may need to consider what type of treatments to prescribe to pregnant mothers with epilepsy.

Role of Maternal Diet in the Risk of Childhood Acute Leukemia: A Systematic Review and Meta-Analysis

Many studies have investigated the etiology of acute leukemia, one of the most common types of cancer in children; however, there is a lack of clarity regarding preventable risk factors. This systematic review and meta-analysis aimed to summarize the current evidence regarding the role of maternal dietary factors in the development of childhood leukemia. All epidemiological studies published until July 2022 that evaluated maternal dietary risk factors for childhood acute leukemia were identified in two electronic databases (PubMed and Web of Science) without limits of publication year or language. A total of 38 studies (1 prospective cohort study, 34 case-control studies and 3 studies with pooled analysis) were included. The published risk estimates were combined into a meta-analysis, using the Generic Inverse Variance method. The maternal consumption of fruits (two or more daily servings vs. less) was inversely associated with acute lymphoblastic leukemia (odds ratio = 0.71; 95% CI, 0.59-0.86), whereas maternal coffee intake (higher than two cups per day vs. no consumption) was associated with an increased risk of acute lymphoblastic leukemia (odds ratio = 1.45; 95% CI, 1.12-1.89). Despite these findings, more high-quality research from cohort studies and the identification of causal factors are needed to develop evidence-based and cost-effective prevention strategies applicable at the population level. Review Registration: PROSPERO registration no. CRD42019128937.

Maternal antibiotics exposure during pregnancy and the risk of acute lymphoblastic leukemia in childhood: a systematic review and meta-analysis

Many epidemiological studies have assessed the association between maternal antibiotic exposure during pregnancy and childhood acute lymphoblastic leukemia (ALL), while reaching inconsistent conclusions. In order to clarify the association, the publications in English that provided information about maternal antibiotic exposure during pregnancy and ALL risk in offspring in the PubMed, Embase, and Web of Science databases were systematically reviewed and we performed a meta-analysis using the random-effect models. Results of pooled analysis showed that maternal antibiotic intake during pregnancy is not associated with childhood ALL risk (pooled odds ratio 1.07, 95% confidence interval 0.98-1.18) without significant heterogeneity (I² = 13.7%, P = 0.310). This finding was consistent across subgroups stratified by type of study design, measurement method, sample size, study quality, and pregnancy stage. Our findings suggest that maternal antibiotic consumption during pregnancy was not associated with ALL risk in progeny. Further investigations are needed to confirm the results and assess any risk differences of ALL by types of antibiotics.Conclusions: Our findings suggest that maternal antibiotics consumption during pregnancy was not associated with ALL risk in progeny. Further investigations are needed to confirm the results and assess any risk differences of ALL by types of antibiotics. What is Known: • It is not unusual for pregnant woman to receive antibiotics for local or systematic use during pregnancy. • The conclusions regarding the associations between maternal antibiotics use during pregnancy and childhood ALL risk were inconsistent. What is New: • Maternal antibiotics consumption during pregnancy was not associated with the increased ALL risk in offspring. • Further laboratory evidences are needed to confirm the results.

Maternal Medication Use and Childhood Cancer in Offspring-Systematic Review and Considerations for Researchers

Cancer is an important cause of childhood mortality, yet the etiology is largely unknown. A combination of pre- and postnatal factors is thought to be implicated, including maternal medication use. We aimed to provide: 1) a systematic review of peer-reviewed publications on associations between maternal medication use and childhood cancer, with a focus on study design and methodology; and 2) suggestions for how to increase transparency, limit potential biases, and improve comparability in studies on maternal medication use and childhood cancer. We conducted a systematic search in the PubMed, Embase, Scopus, Cochrane, and Web of Science databases to June 8, 2020. Altogether, 112 studies were identified. The reviewed studies were heterogeneous in study design, exposure, and outcome classification. In 21 studies (19%), the outcome was any childhood cancer. Of the 91 papers that reported on specific types of cancer, 62% did not report the cancer classification system. The most frequently investigated medication groups were sex hormones (46 studies, excluding fertility medications), and antiinfectives (37 studies). Suggestions for strengthening future pharmacoepidemiologic studies on maternal medication use and childhood cancer relate to choice of cancer classification system, exposure windows, and methods for identification of, and control for, potential confounders.

The Protective Effect of Maternal Folic Acid Supplementation on Childhood Cancer: A Systematic Review and Meta-analysis of Case-control Studies

OBJECTIVES

Maternal folic acid supplementation is considered mandatory in almost every country in the world to prevent congenital malformations. However, little is known about the association of maternal folic acid intake with the occurrence of childhood cancer. Hence, this study aimed to determine the effects of maternal folic acid consumption on the risk of childhood cancer.

METHODS

A total of 158 related articles were obtained from PubMed, Google Scholar, Scopus, and ProQuest using standardized keywords, of which 17 were included in the final review.

RESULTS

Eleven of the 17 articles showed a significant protective association between maternal folic acid supplementation and childhood cancer. Using a random-effects model, pooled odds ratios (ORs) showed a protective association between maternal folic acid supplementation and childhood acute lymphoblastic leukaemia (OR, 0.75; 95% confidence interval [CI], 0.66 to 0.86). However, there was no significant association between maternal folic acid supplementation and acute myeloid leukaemia (OR, 0.70; 95% CI, 0.46 to 1.06) or childhood brain tumours (OR, 1.02; 95% CI, 0.88 to 1.19).

CONCLUSIONS

Maternal folic acid supplementation was found to have a protective effect against childhood acute lymphoblastic leukaemia. Thus, healthcare professionals are recommended to provide regular health education and health promotion to the community on the benefits of folic acid supplementation during pregnancy.

CD3D and PRKCQ work together to discriminate between B-cell and T-cell acute lymphoblastic leukemia

Different therapeutic methods have been developed for the B-cell and T-cell subtypes of acute lymphoblastic leukemia (ALL). The identification of molecular biomarkers that can accurately discriminate between B-cell and T-cell ALLs will facilitate the quick determination of therapeutic plans, as well as reveal the intrinsic mechanisms underlining the two different ALL subtypes. This study computationally screened the high-throughput transcriptome dataset for multiple candidate biomarkers and verified their discrimination abilities in an independent sample set using quantitative real-time polymerase chain reaction (PCR) technology. Both technologies suggest that the two genes CD3D and PKRCQ together provided a good model for classification of B-cell and T-cell ALLs, whereas the individual genes did not show consistent discrimination between the two ALL subtypes. Supplementary material is available at http://healthinformaticslab.org/supp/.

Chlorpyrifos Induces MLL Translocations Through Caspase 3-Dependent Genomic Instability and Topoisomerase II Inhibition in Human Fetal Liver Hematopoietic Stem Cells

Household pesticide exposure during pregnancy has been associated with a more than 2-fold increased risk in infant leukemia, and chlorpyrifos (CPF) is among the most frequently applied insecticides. During early fetal development, liver is a hematopoietic organ with majority of cells being CD34(+) hematopoietic stem cells (CD34(+)HSC). The in utero injury to CD34(+)HSC has been known to underlie the pathogenesis of several blood disorders, often involving rearrangements of the mixed-lineage leukemia (MLL) gene on 11q23. In this study, we evaluated the leukemogenic potential of CPF in human fetal liver-derived CD34(+)HSC. Specifically, exposure to 10 μM CPF led to decrease in viability, inhibition in proliferation and induction of DNA double-strand breaks (DSBs) and occurrence of MLL(+) rearrangements. In particular, we observed CPF-mediated cell cycle disturbance as shown by G0/G1 arrest, in contrast to etoposide (VP-16), an anticancer drug used as a positive control and known to induce G2/M arrest. Further study on mechanisms underlying DNA DSBs and MLL(+) rearrangements revealed that CPF might act as topoisomerase II poison, a mechanism of action similar to VP-16. On the other hand, CPF was also shown to induce early apoptosis through active caspase-3 activation, a pathway known to underlie DNA DSBs and MLL(+) translocations. Our data indicate that in utero injury of CD34(+)HSC by CPF may contribute to the increased risk of infant leukemia. Future work will elucidate the mechanism and the type of CPF-induced MLL(+) translocations in HSC.

Antibiotic use from conception to diagnosis of child leukaemia as compared to the background population: A nested case-control study

BACKGROUND

The role of infection in the aetiology of childhood leukaemia is unknown. We used prescriptions of antibiotics from Danish pharmacies as a proxy measure for the occurrence of infections.

PROCEDURE

We investigated the association between exposure to antibiotics, from conception to leukaemia diagnosis, and the risk of leukaemia. Incident cases of leukaemia among children in Denmark, 1995-2008, with mothers having their earliest conception date in 1995, were individually matched to population controls by age, sex and municipality. Conditional logistic regression analyses assessed antibiotic redemptions in different time periods from conception up to 6 months before the diagnoses of all leukaemia types, acute lymphoblastic leukaemia [ALL] and ALL in 2- to 5-year-old children, adjusting for several potential confounders.

RESULTS

A total of 120/360 (33.3%) leukaemia mothers and 1,081/3,509 (30.8%) control mothers redeemed antibiotics during pregnancy (P = 0.32). For children, the equivalent numbers were 276 (76.7%) and 2,665 (75.9%) (P = 0.76). Histograms of antibiotic redemptions showed no temporal differences between leukaemia mothers/children and controls, which was confirmed in adjusted regression analyses (OR [95% CI]: 1.02 [0.75-1.38]). Only antibiotics redeemed during the first year after birth differed from this (OR [95% CI] for ALL diagnosed in 2- to 5-year-old children: 0.46 [0.31-0.66]).

CONCLUSIONS

In this hypothesis generating study, the similar amount and pattern of antibiotic redemptions in children with and without leukaemia indicate that infections play a minor role in the aetiology of childhood leukaemia. However, less antibiotic redemptions during the first year of life conform to Greaves' 'delayed infection hypothesis'.

Maternal supplementation with folic acid and other vitamins and risk of leukemia in offspring: a Childhood Leukemia International Consortium study

BACKGROUND

Maternal prenatal supplementation with folic acid and other vitamins has been inconsistently associated with a reduced risk of childhood acute lymphoblastic leukemia (ALL). Little is known regarding the association with acute myeloid leukemia (AML), a rarer subtype.

METHODS

We obtained original data on prenatal use of folic acid and vitamins from 12 case-control studies participating in the Childhood Leukemia International Consortium (enrollment period: 1980-2012), including 6,963 cases of ALL, 585 cases of AML, and 11,635 controls. Logistic regression was used to estimate pooled odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for child's age, sex, ethnicity, parental education, and study center.

RESULTS

Maternal supplements taken any time before conception or during pregnancy were associated with a reduced risk of childhood ALL; odds ratios were 0.85 (95% CI = 0.78-0.92) for vitamin use and 0.80 (0.71-0.89) for folic acid use. The reduced risk was more pronounced in children whose parents' education was below the highest category. The analyses for AML led to somewhat unstable estimates; ORs were 0.92 (0.75-1.14) and 0.68 (0.48-0.96) for prenatal vitamins and folic acid, respectively. There was no strong evidence that risks of either types of leukemia varied by period of supplementation (preconception, pregnancy, or trimester).

CONCLUSIONS

Our results, based on the largest number of childhood leukemia cases to date, suggest that maternal prenatal use of vitamins and folic acid reduces the risk of both ALL and AML and that the observed association with ALL varied by parental education, a surrogate for lifestyle and sociodemographic characteristics.

Maternal dietary intake of folate and vitamins B6 and B12 during pregnancy and the risk of childhood acute lymphoblastic leukemia

Our aim was to address the hypothesis that maternal dietary intake of folate during pregnancy is inversely associated with risk of acute lymphoblastic leukemia (ALL) in the offspring. Dietary intake of folate, vitamins B6 and B12 in the last 6 mo of pregnancy from 333 cases and 695 frequency-matched controls were assessed using a food frequency questionnaire. Data were analyzed using unconditional logistic regression, adjusting for study matching variables, total energy, and potentially confounding variables. Higher levels of dietary folate and B12 appeared to be associated with a decreased risk of ALL. Higher levels of vitamin B6 were associated with an increased risk. The strongest associations of ALL with these variables were seen when mothers consumed alcohol in pregnancy. Our findings are consistent with a modest protective effect of higher dietary intake of folate and vitamin B12 against ALL in the offspring, more particularly among women who drank alcohol during pregnancy. These findings are consistent with previous reports of the protective effects of a maternal diet high in fruit, vegetables, and nondairy protein sources. The vitamin B6 findings are not consistent with evidence that it is a protective factor against other cancers, and may be a chance finding.

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.

Analgesic use during pregnancy and risk of infant leukaemia: a Children's Oncology Group study

Background:

Infant leukaemia is likely initiated in utero.

Methods:

We examined whether analgesic use during pregnancy was associated with risk by completing telephone interviews of the mothers of 441 infant leukaemia cases and 323 frequency-matched controls, using unconditional logistic regression.

Results:

With the exception of a reduced risk for infant acute myeloid leukaemias with non-aspirin non-steroidal anti-inflammatory drugs (NSAID) use early in pregnancy (odds ratios=0.60; confidence intervals: 0.37–0.97), no statistically significant associations were observed for aspirin, non-aspirin NSAIDs, or acetaminophen use in early pregnancy or after knowledge of pregnancy.

Conclusion:

Overall, analgesic use during pregnancy was not significantly associated with the risk of infant leukaemia.

Maternal use of antibiotics and cancer in the offspring: results of a case-control study in Germany

OBJECTIVE

As previous results were inconsistent, we assessed the association between maternal use of antibiotics during pregnancy or 3 months before conception and childhood cancer in the offspring in a large case-control study in Germany.

METHODS

This population-based study on potential risk factors for childhood cancer was conducted by the German Childhood Cancer Registry (GCCR) and included a total of 1,867 registered cancer cases aged 0-14, diagnosed between October 1992 and September 1994. A total of 2,057 controls were randomly drawn from population registries, matched by age, gender, and region. Conditional logistic regression models for frequency-matched datasets were used to estimate odds ratios (OR) with 95% confidence intervals (95% CI).

RESULTS

Positive statistically significant associations with self-reported maternal antibiotic use were observed for acute lymphoid leukemia (based on 59 mothers exposed to antibiotics, OR = 1.47; 95% CI: 1.06-2.04), acute myeloid leukemia (18 exposed, OR = 3.21; 95% CI: 1.83-5.62), and Burkitt lymphoma (three exposed, OR = 5.89; 95% CI: 1.47-23.69), but not other cancer types.

CONCLUSIONS

The results provide some support for the hypothesis that maternal use of antibiotics increases the risk of cancer in the offspring. Although recall bias is a concern, it is unlikely that this fully explains the observed effect. Further, the observed associations might be related to the underlying infections.

Pediatric cancer rates after universal folic acid flour fortification in Ontario

Following the introduction of mandatory Canadian folic acid flour fortification in mid-1997, the incidence of selected childhood cancers that declined in Ontario prior to and subsequent to this public policy initiative was examined. A population-based cohort study of all incident cases of childhood malignancy in Ontario between the years 1985 and 2006 was conducted. Participants were identified from a database provided by the Pediatric Oncology Group of Ontario and included children 0 to 4 years of age and 5 to 9 years of age who were diagnosed with cancer. Among children aged 0 to 4 years, the incidence rate of Wilms' tumor declined from 1.94 to 1.43 per 100,000 (incidence rate ratio 0.74, 95% confidence interval, 0.57-0.95). No significant change was seen in the prefortification vs postfortification time periods for acute lymphoblastic leukemia, brain cancers, or embryonal cancers among the 0- to 4-year or 5- to 9-year age groups. There was an approximately 30% reduction in risk of Wilms' tumor following introduction of the initiative. This corroborates a recent case-control study from Germany. These data may also provide some reassurance that universal flour fortification does not heighten the risk of pediatric cancer.

Maternal folate and other vitamin supplementation during pregnancy and risk of acute lymphoblastic leukemia in the offspring

The Australian Study of Causes of Acute Lymphoblastic Leukemia in Children (Aus-ALL) was designed to test the hypothesis, raised by a previous Western Australian study, that maternal folic acid supplementation during pregnancy might reduce the risk of childhood acute lymphoblastic leukemia (ALL). Aus-ALL was a national, population-based, multicenter case-control study that prospectively recruited 416 cases and 1,361 controls between 2003 and 2007. Detailed information was collected about maternal use of folic acid and other vitamin supplements before and during the index pregnancy. Data were analyzed using logistic regression, adjusting for matching factors and potential confounders. A meta-analysis with the results of previous studies of folic acid supplementation was also conducted. We found weak evidence of a protective effect of maternal folate supplementation before pregnancy against risk of childhood ALL, but no evidence for a protective effect of its use during pregnancy. A meta-analysis including this and 2 other studies, but not the study that raised the hypothesis, also found little evidence that folate supplementation during pregnancy protects against ALL: the summary odds ratios (ORs) for folate supplementation were 1.06 [95% confidence interval (CI): 0.77-1.48] with reference to no folate supplementation and 1.02 (95% CI: 0.86-1.20) with reference to no vitamin supplementation. For vitamin supplementation in general, the summary OR from a meta-analysis of 5 studies-including Aus-ALL-was 0.83 (95% CI: 0.73-0.94). Vitamin supplementation in pregnancy may protect against childhood ALL, but this effect is unlikely to be large or, if real, specifically due to folate.

Infant leukemia and parental infertility or its treatment: a Children's Oncology Group report

BACKGROUND

Little is known about the potential risk factors for infant leukemia. With its very young age at diagnosis, exposures occurring in the perinatal period are suspected. Parental infertility and infertility treatment have been studied with regard to childhood cancer in general, but rarely in individual cancer subtypes.

METHODS

A case-control study of infant leukemia was conducted through the Children's Oncology Group, including cases diagnosed from January 1996 to December 2006 and controls selected through random digit dialing and birth certificate tracing. Maternal phone interviews were conducted to obtain information about infertility, infertility treatment and demographic factors. All cases as well as subgroups defined by mixed lineage leukemia (MLL) translocation status and leukemia subtype were examined. Statistical analysis was performed using multivariate logistic regression models.

RESULTS

No significant associations between infertility or its treatment and combined infant leukemia were found. In subgroup analyses, there was a significant increase in the risk of MLL--leukemia for children born to women not trying to conceive compared with those trying for <1 year for all types combined [odds ratio (OR) = 1.62, 95% confidence interval (CI) = 1.01-2.59] and for acute lymphoblastic leukemia (OR = 2.50, 95% CI = 1.36-4.61).

CONCLUSIONS

There were no positive associations between parental infertility or infertility treatment and infant leukemia. While this is the largest study to date, both selection and recall bias may have impacted the results. However, for infant leukemia, we can potentially rule out large increases in risk associated with parental infertility or its treatment.

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.

Vitamin and mineral supplements in pregnancy and the risk of childhood acute lymphoblastic leukaemia: a case-control study

Background

An earlier case-control study from Western Australia reported a protective effect of maternal folic acid supplementation during pregnancy on the risk of childhood acute lymphoblastic leukaemia (ALL). The present study tested that association.

Methods

A national case-control study was conducted in New Zealand. The mothers of 97 children with ALL and of 303 controls were asked about vitamin and mineral supplements taken during pregnancy.

Results

There was no association between reported folate intake during pregnancy and childhood ALL (adjusted odds ratio (OR) 1.1, 95% confidence interval (CI) 0.5–2.7). Combining our results with the study from Western Australia and another study from Québec in a meta-analysis gave a summary OR of 0.9 (95% CI 0.8–1.1).

Conclusion

Our own study, of similar size to the Australian study, does not support the hypothesis of a protective effect of folate on childhood ALL. Neither do the findings of the meta-analysis.

Medication use during pregnancy and the risk of childhood cancer in the offspring

The young age at onset of many cancers in childhood has led to investigations on maternal exposures during pregnancy. Data from a population-based case-control study in Germany (1992-1997) that included 1,867 cases and 2,057 controls was used to investigate this question. Maternal use of vitamin, folate or iron supplementation was associated with a reduced risk of non-Hodgkin lymphoma and tumors and, less clearly, with leukemia, but not with CNS tumors. An increased risk of neuroblastoma was associated most markedly with diuretics and other antihypertensives, but also with vitamin, folate or iron supplementation. No associations were seen with pain relievers, antinauseants or cold medications, nor with delivery by Caesarian section. The strengths of this study are its population base, the large number of cases and the inclusion of different case groups to identify disease specificity of associations. The limitation of this study is an exposure assessment relying on maternal self-reports. In conclusion, these data indicate a potential influence of some maternal medication during pregnancy on the risk of childhood cancer in the offspring; however, no clear picture is seen.

Childhood acute lymphocytic leukemia and perspectives on risk assessment of early-life stage exposures

Recognition that children are a potentially susceptible subpopulation has led to the development of child-specific sensitivity factors. Establishing reliable sensitivity factors in support of risk assessment of early-life stage exposures can be aided by evaluating studies that enhance our understanding both of the biological basis of disease processes and the potential role of environmental exposures in disease etiology. For these reasons, we evaluated childhood acute lymphocytic leukemia (ALL) studies from the point of view of mechanism and etiology. ALL is the most common form of childhood cancer proposed to result from a prenatal primary event and a postnatal second event. This multi-stage model is supported by the observation that chromosomal translocations/fusion genes (e.g., TEL-AML1) involved in producing ALL are detected at birth (prenatal event), and a postnatal event (e.g., TEL deletion) is required for disease manifestation. It appears that a proportion of ALL cases are the result of environmental exposures, in which case preconceptional, prenatal, and postnatal stages are likely to be critical exposure windows. To this end, we recognized postnatal infection-related risk factors as potential candidates associated with the ALL second event. Additionally, we discuss use of ALL-associated fusion genes and genetic polymorphisms, together or separately, as indicators of ALL susceptibility and increased risk. The possibility of using fusion genes alone as biomarkers of response is also discussed because they can serve as predictors of key events in the development of a mode of action (a sequence of key events, starting with interaction of an agent with a cell, ultimately resulting in cancer formation) for particular environmental exposures. Furthermore, we discuss use of an initiated animal model for ALL, namely transgenic mice with TEL-AML1 expression, for exploring mechanisms by which different classes of environmental exposures could be involved in inducing the postnatal step in ALL formation.