A meta-analysis of the association between day-care attendance and childhood acute lymphoblastic leukaemia

Age and ligand specificity influence the outcome of pathogen engagement on preleukemic and leukemic B-cell precursor populations

Common infections have long been proposed to play a role in the development of pediatric B-cell acute lymphoblastic leukemia (B-ALL). However, epidemiologic studies report contradictory effects of infection exposure on subsequent B-ALL risk, and no specific pathogen has been definitively linked to the disease. A unifying mechanism to explain the divergent outcomes could inform disease prevention strategies. We previously reported that the pattern recognition receptor (PRR) ligand Poly(I:C) exerted effects on B-ALL cells that were distinct from those observed with other nucleic acid-based PRR ligands. Here, using multiple double-stranded RNA (dsRNA) moieties, we show that the overall outcome of exposure to Poly(I:C) reflects the balance of opposing responses induced by its ligation to endosomal and cytoplasmic receptors. This PRR response biology is shared between mouse and human B-ALL and can increase leukemia-initiating cell burden in vivo during the preleukemia phase of B-ALL, primarily through tumor necrosis factor α signaling. The age of the responding immune system further influences the impact of dsRNA exposure on B-ALL cells in both mouse and human settings. Overall, our study demonstrates that potentially proleukemic and antileukemic effects can each be generated by the stimulation of pathogen recognition pathways and indicates a mechanistic explanation for the contrasting epidemiologic associations reported for infection exposure and B-ALL.

Association between medically diagnosed postnatal infection and childhood cancers: A matched case-control study in Denmark, 1978 to 2016

Although the association between infection and childhood cancer has been long investigated, there is limited information on rarer cancers. This article aimed to explore the association between postnatal infection and childhood cancers in the Danish population. A matched case-control study was conducted using Danish nationwide registries from 1978 to 2016. Each childhood cancer case was matched 1:25 with controls by birth date within a week and sex. Postnatal infections were identified from the Danish National Patient Registry, which lists diagnoses seen in hospital, specialist or emergency care services. Multivariable conditional logistic regression was used to estimate adjusted odds ratios (adj.OR) and 95% confidence intervals (CI). Specific types of infections and the number of infection episodes were also considered. The study included 4125 childhood cancer cases and 103 526 matched controls with ages ranging from 0 to 19 years. Medically diagnosed postnatal infections were positively associated with many types of childhood cancer including acute lymphoblastic leukemia (adj.OR = 1.42; 95% CI: 1.23-1.63), acute myeloid leukemia (adj.OR = 1.80; 95% CI: 1.28-2.52), non-Hodgkin lymphoma (adj.OR = 1.53; 95% CI: 1.19-1.97) and central nervous system tumors (adj.OR = 1.57; 95% CI: 1.39-1.77). A higher number of infection episodes were also associated with an increased risk of these cancers. Specific infections such as viral, enteric and urinary tract infections were also strongly associated with specific types of cancer. In conclusion, children who later develop cancer appear to have adverse reactions to infections necessitating referral to specialized health care services, perhaps indicating dysregulated immune function.

Immune stress suppresses innate immune signaling in preleukemic precursor B-cells to provoke leukemia in predisposed mice

The initial steps of B-cell acute lymphoblastic leukemia (B-ALL) development usually pass unnoticed in children. Several preclinical studies have shown that exposure to immune stressors triggers the transformation of preleukemic B cells to full-blown B-ALL, but how this takes place is still a longstanding and unsolved challenge. Here we show that dysregulation of innate immunity plays a driving role in the clonal evolution of pre-malignant Pax5+/- B-cell precursors toward leukemia. Transcriptional profiling reveals that Myd88 is downregulated in immune-stressed pre-malignant B-cell precursors and in leukemic cells. Genetic reduction of Myd88 expression leads to a significant increase in leukemia incidence in Pax5+/-Myd88+/- mice through an inflammation-dependent mechanism. Early induction of Myd88-independent Toll-like receptor 3 signaling results in a significant delay of leukemia development in Pax5+/- mice. Altogether, these findings identify a role for innate immunity dysregulation in leukemia, with important implications for understanding and therapeutic targeting of the preleukemic state in children.

Gut microbiome immaturity and childhood acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) is the most common cancer of childhood. Here, we map emerging evidence suggesting that children with ALL at the time of diagnosis may have a delayed maturation of the gut microbiome compared with healthy children. This finding may be associated with early-life epidemiological factors previously identified as risk indicators for childhood ALL, including caesarean section birth, diminished breast feeding and paucity of social contacts. The consistently observed deficiency in short-chain fatty-acid-producing bacterial taxa in children with ALL has the potential to promote dysregulated immune responses and to, ultimately, increase the risk of transformation of preleukaemic clones in response to common infectious triggers. These data endorse the concept that a microbiome deficit in early life may contribute to the development of the major subtypes of childhood ALL and encourage the notion of risk-reducing microbiome-targeted intervention in the future.

Does congenital cytomegalovirus infection contribute to the development of acute lymphoblastic leukemia in children?

Cytomegalovirus (CMV) is a ubiquitous herpesvirus that has a profound impact on the host immune system. Congenital cytomegalovirus (cCMV) infection modulates neonatal immune cell compartments, yet the full impact of in utero exposure on developing fetal immune cells remains poorly characterized. A series of recent studies have identified a potential link between cCMV infection and the development of acute lymphoblastic leukemia (ALL) in childhood. Here, we review the emerging evidence linking CMV and ALL risk, discuss what is known about the causes of childhood ALL, and propose how CMV infection in early life may confer increased ALL risk.

Childcare attendance and risk of childhood acute lymphoblastic leukaemia: A register study based on the Danish childcare database

Childhood acute lymphoblastic leukaemia (ALL) is suggested to result from a dysregulated immune response to infections in children with a preleukaemic state. Childcare in early life supposedly may protect against childhood ALL by facilitating sufficient exposure to infections to stimulate and ensure normal maturation of the immune system. We assessed the association between childcare attendance before age 2 years and risk of childhood ALL in a register-based cohort study, including all children aged 2 to 14 years born in Denmark during 1991 to 2014 with available childcare information recorded in the Danish Childcare Database (n = 1 116 185). Cox regression was used to estimate hazard ratios (HRs) comparing children enrolled in childcare and children not enrolled before age 2 years. Further, we assessed the association according to age at enrolment, type of childcare facility and specific ALL subtypes. During 10 460 811 person-years of follow-up, 460 children developed ALL at ages 2 to 14 years. Of these, 57 (12.4%) never attended childcare before age 2 years compared with 10.6% in the total cohort. Compared with homecare, childcare attendance before age 2 years was associated with a statistically non-significantly, marginally decreased risk of childhood ALL with adjusted HR = 0.87 (95% confidence interval [CI]: 0.65-1.16). Risk estimates did neither vary statistically significantly by age at enrolment nor by type of childcare facility and also not between childhood ALL subtypes, including frequently prenatally initiated ALL subtypes. Results from this large, nationwide register-based study provided no evidence that childcare attendance in the first years of life protects against childhood ALL.

Interaction between maternal killer immunoglobulin-like receptors and offspring HLAs and susceptibility of childhood ALL

Acute lymphoblastic leukemia (ALL) in children is associated with a distinct neonatal cytokine profile. The basis of this neonatal immune phenotype is unknown but potentially related to maternal-fetal immune receptor interactions. We conducted a case-control study of 226 case child-mother pairs and 404 control child-mother pairs to evaluate the role of interaction between HLA genotypes in the offspring and maternal killer immunoglobulin-like receptor (KIR) genotypes in the etiology of childhood ALL, while considering potential mediation by neonatal cytokines and the immune-modulating enzyme arginase-II (ARG-II). We observed different associations between offspring HLA-maternal KIR activating profiles and the risk of ALL in different predicted genetic ancestry groups. For instance, in Latino subjects who experience the highest risk of childhood leukemia, activating profiles were significantly associated with a lower risk of childhood ALL (odds ratio [OR] = 0.59; 95% confidence interval [CI], 0.49-0.71) and a higher level of ARG-II at birth (coefficient = 0.13; 95% CI, 0.04-0.22). HLA-KIR activating profiles were also associated with a lower risk of ALL in non-Latino Asians (OR = 0.63; 95% CI, 0.38-1.01), although they had a lower tumor necrosis factor-α level (coefficient = -0.27; 95% CI, -0.49 to -0.06). Among non-Latino White subjects, no significant association was observed between offspring HLA-maternal KIR interaction and ALL risk or cytokine levels. The current study reports the association between offspring HLA-maternal KIR interaction and the development of childhood ALL with variation by predicted genetic ancestry. We also observed some associations between activating profiles and immune factors related to cytokine control; however, cytokines did not demonstrate causal mediation of the activating profiles on ALL risk.

Environmental Risk Factors for Childhood Acute Lymphoblastic Leukemia: An Umbrella Review

Leukemia is the most common type of cancer among children and adolescents worldwide. The aim of this umbrella review was (1) to provide a synthesis of the environmental risk factors for the onset of childhood acute lymphoblastic leukemia (ALL) by exposure window, (2) evaluate their strength of evidence and magnitude of risk, and as an example (3) estimate the prevalence in the German population, which determines the relevance at the population level. Relevant systematic reviews and pooled analyses were identified and retrieved through PubMed, Web of Science databases and lists of references. Only two risk factors (low doses of ionizing radiation in early childhood and general pesticide exposure during maternal preconception/pregnancy) were convincingly associated with childhood ALL. Other risk factors including extremely low frequency electromagnetic field (ELF-MF), living in proximity to nuclear facilities, petroleum, benzene, solvent, and domestic paint exposure during early childhood, all showed some level of evidence of association. Maternal consumption of coffee (high consumption/>2 cups/day) and cola (high consumption) during pregnancy, paternal smoking during the pregnancy of the index child, maternal intake of fertility treatment, high birth weight (≥4000 g) and caesarean delivery were also found to have some level of evidence of association. Maternal folic acid and vitamins intake, breastfeeding (≥6 months) and day-care attendance, were inversely associated with childhood ALL with some evidence. The results of this umbrella review should be interpreted with caution; as the evidence stems almost exclusively from case-control studies, where selection and recall bias are potential concerns, and whether the empirically observed association reflect causal relationships remains an open question. Hence, improved exposure assessment methods including accurate and reliable measurement, probing questions and better interview techniques are required to establish causative risk factors of childhood leukemia, which is needed for the ultimate goal of primary prevention.

Antibiotics in early life and childhood pre-B-ALL. Reasons to analyze a possible new piece in the puzzle

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer with precursor B-cell ALL (pB-ALL) accounting for ~ 85% of the cases. Childhood pB-ALL development is influenced by genetic susceptibility and host immune responses. The role of the intestinal microbiome in leukemogenesis is gaining increasing attention since Vicente-Dueñas' seminal work demonstrated that the gut microbiome is distinct in mice genetically predisposed to ALL and that the alteration of this microbiome by antibiotics is able to trigger pB-ALL in Pax5 heterozygous mice in the absence of infectious stimuli. In this review we provide an overview on novel insights on the role of the microbiome in normal and preleukemic hematopoiesis, inflammation, the effect of dysbiosis on hematopoietic stem cells and the emerging importance of the innate immune responses in the conversion from preleukemic to leukemic state in childhood ALL. Since antibiotics, which represent one of the most widely used medical interventions, alter the gut microbial composition and can cause a state of dysbiosis, this raises exciting epidemiological questions regarding the implications for antibiotic use in early life, especially in infants with a a preleukemic "first hit". Sheading light through a rigorous study on this piece of the puzzle may have broad implications for clinical practice.

Identification of Genetic Predispositions Related to Ionizing Radiation in Primary Human Skin Fibroblasts From Survivors of Childhood and Second Primary Cancer as Well as Cancer-Free Controls: Protocol for the Nested Case-Control Study KiKme

BACKGROUND

Therapy for a first primary neoplasm (FPN) in childhood with high doses of ionizing radiation is an established risk factor for second primary neoplasms (SPN). An association between exposure to low doses and childhood cancer is also suggested; however, results are inconsistent. As only subgroups of children with FPNs develop SPNs, an interaction between radiation, genetic, and other risk factors is presumed to influence cancer development.

OBJECTIVE

Therefore, the population-based, nested case-control study KiKme aims to identify differences in genetic predisposition and radiation response between childhood cancer survivors with and without SPNs as well as cancer-free controls.

METHODS

We conducted a population-based, nested case-control study KiKme. Besides questionnaire information, skin biopsies and saliva samples are available. By measuring individual reactions to different exposures to radiation (eg, 0.05 and 2 Gray) in normal somatic cells of the same person, our design enables us to create several exposure scenarios for the same person simultaneously and measure several different molecular markers (eg, DNA, messenger RNA, long noncoding RNA, copy number variation).

RESULTS

Since 2013, 101 of 247 invited SPN patients, 340 of 1729 invited FPN patients, and 150 of 246 invited cancer-free controls were recruited and matched by age and sex. Childhood cancer patients were additionally matched by tumor morphology, year of diagnosis, and age at diagnosis. Participants reported on lifestyle, socioeconomical, and anthropometric factors, as well as on medical radiation history, health, and family history of diseases (n=556). Primary human fibroblasts from skin biopsies of the participants were cultivated (n=499) and cryopreserved (n=3886). DNA was extracted from fibroblasts (n=488) and saliva (n=510).

CONCLUSIONS

This molecular-epidemiological study is the first to combine observational epidemiological research with standardized experimental components in primary human skin fibroblasts to identify genetic predispositions related to ionizing radiation in childhood and SPNs. In the future, fibroblasts of the participants will be used for standardized irradiation experiments, which will inform analysis of the case-control study and vice versa. Differences between participants will be identified using several molecular markers. With its innovative combination of experimental and observational components, this new study will provide valuable data to forward research on radiation-related risk factors in childhood cancer and SPNs.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/32395.

Decreased IL-10 accelerates B-cell leukemia/lymphoma in a mouse model of pediatric lymphoid leukemia

B-cell deficiency and DNA damage in the bone marrow of Il10^−/− mice are associated with inflammation and mitigated by antibiotics.

In ETV6-RUNX1⁺Cdkn2a^−/− mice, low IL-10 accelerates the development of B-cell leukemia/lymphoma in a dose-dependent manner.

Exposures to a wide repertoire of common childhood infections and strong inflammatory responses to those infections are associated with the risk of pediatric B-cell acute lymphoblastic leukemia (B-ALL) in opposing directions. Neonatal inflammatory markers are also related to risk by unknown mechanism(s). Here, we demonstrate that interleukin-10 (IL-10) deficiency, which is associated with childhood B-ALL, indirectly impairs B lymphopoiesis and increases B-cell DNA damage in association with a module of 6 proinflammatory/myeloid-associated cytokines (IL-1α, IL-6, IL-12p40, IL-13, macrophage inflammatory protein-1β/CCL4, and granulocyte colony-stimulating factor). Importantly, antibiotics attenuated inflammation and B-cell defects in preleukemic Cdkn2a^−/−Il10^−/− mice. In an ETV6-RUNX1⁺ (E6R1⁺) Cdkn2a^−/− mouse model of B-ALL, decreased levels of IL-10 accelerated B-cell neoplasms in a dose-dependent manner and altered the mutational profile of these neoplasms. Our results illuminate a mechanism through which a low level of IL-10 can create a risk for leukemic transformation and support developing evidence that microbial dysbiosis contributes to pediatric B-ALL.

Infectious triggers and novel therapeutic opportunities in childhood B cell leukaemia

B cell acute lymphoblastic leukaemia (B-ALL) is the most common form of childhood cancer. Although treatment has advanced remarkably in the past 50 years, it still fails in ~20% of patients. Recent studies revealed that more than 5% of healthy newborns carry preleukaemic clones that originate in utero, but only a small percentage of these carriers will progress to overt B-ALL. The drivers of progression are unclear, but B-ALL incidence seems to be increasing in parallel with the adoption of modern lifestyles. Emerging evidence shows that a major driver for the conversion from the preleukaemic state to the B-ALL state is exposure to immune stressors, such as infection. Here, we discuss our current understanding of the environmental triggers and genetic predispositions that may lead to B-ALL, highlighting lessons from epidemiology, the clinic and animal models, and identifying priority areas for future research.

Infections and the development of childhood acute lymphoblastic leukemia: a population-based study

An infectious trigger for childhood acute lymphoblastic leukemia is hypothesized and we assessed the association between the rate, type, and critical exposure period for infections and the development of acute lymphoblastic leukemia. We conducted a matched case-control study using administrative databases to evaluate the association between the rate of infections and childhood acute lymphoblastic leukemia diagnosed between the ages of 2-14 years from Ontario, Canada and we used a validated approach to measure infections. In 1600 cases of acute lymphoblastic leukemia, and 16 000 matched cancer-free controls aged 2-14 years, having >2 infections/year increased the odds of childhood acute lymphoblastic leukemia by 43% (odds ratio = 1.43, 95% confidence interval 1.13-1.81) compared to children with ≤0.25 infections/year. Having >2 respiratory infections/year increased odds of acute lymphoblastic leukemia by 28% (odds ratio =1.28, 95% confidence interval 1.05-1.57) compared to children with ≤0.25 respiratory infections/year. Having an invasive infection increased the odds of acute lymphoblastic leukemia by 72% (odds ratio =1.72, 95% confidence interval 1.31-2.26). Having an infection between the age of 1-1.5 years increased the odds of acute lymphoblastic leukemia by 20% (odds ratio = 1.20, 95% confidence interval 1.04-1.39). Having more infections increased the odds of developing childhood acute lymphoblastic leukemia and having an infection between the ages of 1-1.5 years increased the odds of childhood acute lymphoblastic leukemia.

Racial and ethnic disparities in pediatric cancer incidence among children and young adults in the United States by single year of age

BACKGROUND

Incidence rates of pediatric cancers in the United States are typically reported in 5-year age groups, obscuring variation by single year of age. Additionally, racial and ethnic variation in incidence is typically presented in broad categories rather than by narrow age ranges.

METHODS

The Surveillance, Epidemiology, and End Results (SEER) 18 data (2000-2017) were examined to calculate frequencies and age-adjusted incidence rates among individuals aged birth to 39 years. Incidence rate ratios (IRRs) and 95% confidence intervals (95% CIs) were estimated as the measure of association for rate comparisons by race and Hispanic origin overall and by single year of age.

RESULTS

Several histologic types showed substantial variation in race/ethnicity-specific and overall rates by single year of age. Overall, Black children and young adults experienced substantially decreased incidence of acute lymphoid leukemia (IRR, 0.52; 95% CI, 0.49-0.55) compared to Whites, and this decreased incidence was strongest at ages 1 through 7 years and 16 through 20 years. Hispanic individuals experienced decreased overall incidence of Hodgkin lymphoma (IRR, 0.50; 95% CI, 0.48-0.52) and astrocytoma (IRR, 0.54; 95% CI, 0.52-0.56) and increased risk of acute lymphoblastic leukemia (IRR, 1.46; 95% CI, 1.42-1.51) compared to non-Hispanic Whites, and the increased risk was strongest at ages 10 through 23 years. Substantial decreased risk across many tumor types was also observed for Asian/Pacific Islanders and American Indian/Alaska Natives.

CONCLUSIONS

Examination of incidence rates for pediatric cancers by narrow age groups may provide insights regarding etiological differences in subgroups. Additionally, variation in age-specific incidence rates by race and ethnicity may enable hypothesis generation on drivers of disparities observed.

Cytokine Levels at Birth in Children Who Developed Acute Lymphoblastic Leukemia

BACKGROUND

Prenatal immune development may play an important role in the etiology of childhood acute lymphoblastic leukemia (ALL).

METHODS

Seven cytokines, IL1β, IL4, IL6, IL8, GM-CSF, TNFα, and VEGF, were analyzed in blood spots collected at birth from 1,020 ALL cases and 1,003 controls participating in the California Childhood Leukemia Study. ORs and 95% confidence intervals (95% CI) associated with an interquartile range increment in cytokine levels were calculated using logistic regression, adjusting for sociodemographic and birth characteristics.

RESULTS

We found that patients with ALL were born with higher levels of a group of correlated cytokines than controls [IL1β: OR of 1.18 (95% confidence interval [CI], 1.03-1.35); IL8: 1.19 (1.03-1.38); TNFα: 1.15 (1.01-1.30); VEGF: 1.16 (1.01-1.33)], especially among children of Latina mothers (ORs from 1.31 to 1.40) and for ALL with high hyperdiploidy (ORs as high as 1.27). We found that neonatal cytokine levels were correlated with neonatal levels of endogenous metabolites which had been previously associated with ALL risk; however, there was no evidence that the cytokines were mediating the relationship between these metabolites and ALL risk.

CONCLUSIONS

We posit that children born with altered cytokine levels are set on a trajectory towards an increased risk for subsequent aberrant immune reactions that can initiate ALL.

IMPACT

This is the first study to evaluate the interplay between levels of immunomodulatory cytokines at birth, prenatal exposures, and the risk of childhood ALL.

Towards prevention of childhood ALL by early-life immune training

B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is the most common form of childhood cancer. Chemotherapy is associated with life-long health sequelae and fails in ∼20% of cases. Thus, prevention of leukemia would be preferable to treatment. Childhood leukemia frequently starts before birth, during fetal hematopoiesis. A first genetic hit (eg, the ETV6-RUNX1 gene fusion) leads to the expansion of preleukemic B-cell clones, which are detectable in healthy newborn cord blood (up to 5%). These preleukemic clones give rise to clinically overt leukemia in only ∼0.2% of carriers. Experimental evidence suggests that a major driver of conversion from the preleukemic to the leukemic state is exposure to immune challenges. Novel insights have shed light on immune host responses and how they shape the complex interplay between (1) inherited or acquired genetic predispositions, (2) exposure to infection, and (3) abnormal cytokine release from immunologically untrained cells. Here, we integrate the recently emerging concept of “trained immunity” into existing models of childhood BCP-ALL and suggest future avenues toward leukemia prevention.

Vaccination and the Risk of Childhood Cancer-A Systematic Review and Meta-Analysis

INTRODUCTION

Infections may play a role in the etiology of childhood cancer and immunizations may be protective because vaccinations stimulate the immune system. Observational studies reported inconsistent associations between vaccination and risk of childhood cancer. Since a synthesis of the evidence is lacking, we conducted a meta-analysis stratified by histological and site-specific cancer.

METHODS

We performed a systematic review (CRD42020148579) following PRISMA guidelines and searched for literature in MEDLINE, Embase, and the Science Citation Index databases. We identified in three literature databases 7,594 different articles of which 35 met the inclusion criteria allowing for 27 analyses of 11 cancer outcomes after exposure to nine different types of vaccinations. We calculated summary odds ratios (ORs) and 95% confidence intervals (CIs) using random effects models.

RESULTS

We observed four inverse associations between childhood leukemia and certain vaccines as well as the number of vaccinations: OR 0.49 (95% CI = 0.32 to 0.74) for leukemia death after bacillus Calmette-Guérin vaccination; OR 0.76 (95% CI = 0.65 to 0.90) for acute lymphoblastic leukemia after Haemophilus influenzae type b vaccination; OR 0.57 (95% CI = 0.36 to 0.88) for leukemia; and OR 0.62 (95% CI = 0.46 to 0.85) for acute lymphoblastic leukemia after three or more vaccinations of any type. All other conducted analyses did not show any associations.

DISCUSSION

The results are consistent with the hypothesis that vaccinations reduce the risk of childhood leukemia. However, the robustness and validity of these results is limited due to the small number, substantial heterogeneity, and methodological limitations of available studies.

Risikofaktoren für Krebserkrankungen im Kindes- und Jugendalter

Die Ursachen von Krebs im Kindes- und Jugendalter sind weitestgehend unbekannt. Beispiele für konsistent beobachtete Risikofaktoren, die in umfangreichen epidemiologischen Untersuchungen identifiziert wurden, sind Strahlenexposition, Chemotherapie, niedriges und hohes Geburtsgewicht, höheres Alter der Mutter, Geschlecht und das Vorhandensein angeborener Anomalien. Diese Faktoren erklären jedoch nur einen geringen Anteil aller inzidenten Fälle. Die derzeit vielversprechendsten Ansätze zur Verbesserung des Verständnisses über die Ursachen von Krebserkrankungen im Kindes- und Jugendalter stammen von genetischen Analysen. Abgesehen von den durch genomweite Assoziationsstudien identifizierten Allelen mit geringem Krebsrisiko wurde festgestellt, dass seltene Keimbahnvarianten, die Krebsprädispositionsyndrome verursachen, mit einem erhöhten Risiko für die Entwicklung von Krebs im Kindes- und Jugendalter verbunden sind. Dieser Beitrag fasst das aktuelle Wissen über die exogenen und endogenen Ursachen von Krebserkrankungen in den frühen Lebensjahren zusammen und gibt einen Ausblick darauf, wie stetig wachsendes Wissen in diesem Bereich zukünftige präventive, diagnostische und therapeutische Strategien beeinflussen könnte.

Cesarean section and risk of childhood leukemia: a systematic review and meta-analysis

BACKGROUND

A large number of studies pointed that being delivered by cesarean section (CS) would affect the health outcomes of offspring, however, whether CS would affect the risk of childhood leukemia remained uncertain. This study conducted a meta-analysis to quantitatively evaluate whether being delivered by CS would influence the onset of childhood leukemia.

METHODS

PubMed, Embase and Web of Science databases were searched from 3rd June, 1950 to 13th October, 2019 to identify the literature, which examined the relationship between CS and childhood leukemia. This study used Newcastle-Ottawa Scale to assess the quality of literature. Subgroup analyses were conducted on region, mode of delivery, design of the study and number of confounders adjusted. Egger's test and Begg's test were performed to evaluate possible publication bias.

RESULTS

The pooled odds ratio (OR) estimates illustrated that children delivered by CS had a higher risk of developing leukemia [OR 1.10, 95% confidence interval (CI) 1.04-1.17, P = 0.002] and lymphoblastic leukemia (OR 1.12, 95% CI 1.03-1.23, P = 0.009), while a significant association for myeloid leukemia was not observed (OR 1.05, 95% CI 0.92-1.20, P = 0.451). Results of subgroup analyses indicated that elective CS would increase the risk of childhood lymphoblastic leukemia (OR 1.16, 95% CI 1.06-1.27, P = 0.002). However, a statistical relationship between emergency CS and lymphoblastic leukemia was not observed (OR 1.07, 95% CI 0.93-1.23, P = 0.364).

CONCLUSIONS

CS would increase the risk of childhood lymphoblastic leukemia. It is worth noting that subgroup analyses shows that elective CS rather than emergency CS increases the risk of lymphoblastic leukemia in offspring.

History of Early Childhood Infections and Acute Lymphoblastic Leukemia Risk Among Children in a US Integrated Health-Care System

Surrogate measures of infectious exposures have been consistently associated with lower childhood acute lymphoblastic leukemia (ALL) risk. However, recent reports have suggested that physician-diagnosed early-life infections increase ALL risk, thereby raising the possibility that stronger responses to infections might promote risk. We examined whether medically diagnosed infections were related to childhood ALL risk in an integrated health-care system in the United States. Cases of ALL (n = 435) diagnosed between 1994-2014 among children aged 0-14 years, along with matched controls (n = 2,170), were identified at Kaiser Permanente Northern California. Conditional logistic regression was used to estimate risk of ALL associated with history of infections during first year of life and across the lifetime (up to diagnosis). History of infection during first year of life was not associated with ALL risk (odds ratio (OR) = 0.85, 95% confidence interval (CI): 0.60, 1.21). However, infections with at least 1 medication prescribed (i.e., more "severe" infections) were inversely associated with risk (OR = 0.42, 95% CI: 0.20, 0.88). Similar associations were observed when the exposure window was expanded to include medication-prescribed infections throughout the subjects' lifetime (OR = 0.52, 95% CI: 0.32, 0.85).

Race, ethnicity, and socioeconomic differences in incidence of pediatric embryonal tumors in the United States

BACKGROUND

The etiology of childhood cancers and its social patterning remains largely unknown. Accounting for socioeconomic status (SES) when exploring the association between race/ethnicity and cancer incidence is necessary to better understand such etiology. We aimed to investigate differences in the incidence of embryonal tumors (ETs) by SES and race/ethnicity in the United States using population-based registries of the Surveillance, Epidemiology, and End Results (SEER) Program.

PROCEDURE

Children with ETs aged 0-19 years diagnosed between 2000 and 2015 were ascertained from the census tract-level SEER database. SES was measured using a tract-level composite index. Incidence rate ratios (IRRs) with 95% confidence intervals (CIs) by SES quintile and race/ethnicity were estimated using multivariable Poisson regression models.

RESULTS

The majority of tumors had lower incidence among nonwhite children compared with non-Hispanic (NH) white children, after controlling for SES. NH blacks had a higher incidence of Wilms tumor than NH whites (IRR: 1.26; 95% CI, 1.13-1.39). There was an increasing linear trend (P = 0.0001) across increasing SES quintile for embryonal rhabdomyosarcoma after controlling for race/ethnicity. Effect modification by race/ethnicity of the relationship between SES and tumor incidence was observed for several groups. Hispanics had a significant, linear trend (P = 0.0005) in the incidence of Wilms tumor, while Asian/Pacific Islanders experienced a significant inverse trend (P = 0.0002).

CONCLUSIONS

Results from this study suggest differences in the incidence of several ETs by race/ethnicity and that these differences may be modified by SES. Investigation of potential risk factors that are socially patterned is warranted.

Plasma of Acute Lymphoblastic Leukemia Patients React to the Culture of a Mycovirus Containing Aspergillus flavus

Acute lymphoblastic leukemia (ALL) is the most common cancer in children and is also seen in adults. Currently, no plasma-based test for the detection of ALL is available. We have cultured the home of a patient with ALL and isolated a mycovirus containing Aspergillus flavus. This culture was subjected to electron microscopy, purification, and mass spectrometry. Using enzyme-linked immunosorbent assay technique, plasma of patients with ALL and long-term survivors of this disease were tested for antibodies, utilizing supernatant of the culture of this organism. The results were compared with 3 groups of controls, including healthy individuals, patients with sickle cell disease, and solid tumors. Using electron microscopy, the isolated A. flavus contained mycovirus particles. In chemical analysis, this organism did not produce any aflatoxin. Using an enzyme-linked immunosorbent assay technique, the supernatant of the culture of the mycovirus containing A. flavus could differentiate ALL patients from each group of controls (P<0.001). These studies provide a new technique for the detection of ALL and may add information for future research regarding leukemogenesis.

High parental occupational social contact and risk of childhood hematopoietic, brain and bone cancers

BACKGROUND

The etiology of childhood cancer is largely unknown, though some research suggests an infectious origin of hematopoietic, central nervous system (CNS) and bone cancers.

METHODS

We examined parental occupational social contact as a proxy for exposure to infectious agents and risk of childhood cancer. This population-based case-control study utilized a linkage of four Danish data-registries, and included 3581 cases (<17 years, diagnosed 1973-2012) and 358,100 age-matched controls. We examined the risks of leukemia, lymphoma, CNS and bone cancer related to high occupational social contact from (1) conception to birth and (2) birth to diagnosis.

RESULTS

Acute lymphoblastic leukemia (ALL) and bone cancer were inversely associated with high maternal social contact from conception to birth (OR: 0.86, 95% CI: 0.67-1.10) and birth to diagnosis (OR: 0.54, 95% CI: 0.34-0.86). Children of fathers with high social contact from birth to diagnosis had an increased risk of bone cancers, particularly in rural areas (OR: 1.65, 95% CI: 1.03-2.63). Parental social contact was associated with increased risk of astrocytoma, with strongest associations found in first-born children (maternal: OR: 1.54, 95% CI: 1.02-2.32; paternal: OR: 1.82, 95% CI: 1.05-3.17).

CONCLUSION

Our results support the notion of a role of infections for some cancer types.

Risk of Acute Lymphoblastic Leukemia: Results of a Case-Control Study

Background: Acute lymphoblastic leukemia (ALL) is the most common malignancy in children. Different environmental factors might be effective in the occurrence of this malignancy during childhood. The aim of this study was to find environmental risk factors in childhood ALL in Hamadan, Iran. Methods: This case-control study was done in 2015-2018 on 125 children younger than 15 years of age suffering from ALL. Patients were matched with 130 controls with respect to age, gender, and residence location. The identification of risk factors for ALL was sought based on the comparison of studied variables between case and control individuals. Results: A statistically significant increased risk for ALL was found with regard to type of delivery (OR: 0.43, 95% CI: 0.20 - 0.92, p˂0.02), childcare (OR: 4.58, 95% CI: 0.95 - 22.20, p˂0.04), birth weight (OR: 1.44, 95% CI: 1.53 - 2.21, p˂0.006), father’s education level (OR: 2.67, 95% CI: 1.10 - 6.45, p˂0.02), and father’s job (OR: 0.2 95% CI: 0.08 - 0.51, p˂0.001). Also observed were increased odds for ALL regarding male gender, mother’s high education level, mother’s freelance job, and medium or high family income. No association with ALL incidence was observed for age, gender, breastfeeding, mother’s age at pregnancy, malignancy in first- or second-degree relatives, or mother’s use of hair dye during pregnancy (p> 0.05). Conclusion: This study showed that father’s education level, father’s job, delivery type, birth weight, and childcare can play a role in the incidence of childhood ALL.

The sensitivity of reported effects of EMF on childhood leukemia to uncontrolled confounding by residential mobility: a hybrid simulation study and an empirical analysis using CAPS data

PURPOSE

Residential mobility is considered as a potential source of confounding in studies assessing environmental exposures, including in studies of electromagnetic field (EMF) exposures and childhood leukemia.

METHODS

We present a hybrid simulation study where we simulate a synthetic dataset based on an existing study and use it to assess the sensitivity of EMF-leukemia associations to different scenarios of uncontrolled confounding by mobility under two major hypotheses of the infectious etiology of childhood leukemia. We then used the findings to conduct sensitivity analysis and empirically offset the potential bias due to unmeasured mobility in the California Power Line Study dataset.

RESULTS

As expected, the stronger the assumed relationship between mobility and exposure and outcome, the greater the potential bias. However, no scenario created a bias strong enough to completely explain away previously observed associations.

CONCLUSIONS

We conclude that uncontrolled confounding by residential mobility had some impact on the estimated effect of EMF exposures on childhood leukemia, but that it was unlikely to be the primary explanation behind previously observed largely consistent, but unexplained associations.

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

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

Early Infection with Cytomegalovirus and Risk of Childhood Hematologic Malignancies

BACKGROUND

Congenital cytomegalovirus (CMV) infection was recently identified as a risk factor for childhood acute lymphocytic leukemia by detecting the presence of CMV sequences in neonatal blood spots. In this study, we asked whether clinically apparent CMV infection could be identified prior to hematologic malignancy, using high-quality Swedish population-based registries.

METHODS

CMV infection was identified with appropriate ICD-9 or ICD-10 codes in the Patient and Medical Birth Registries, and childhood malignancies below the age of 15 years were identified in the Cancer Registry, among 2,782,507 children born in Sweden 1987 to 2014.

RESULTS

Observing all CMV infections registered earlier than 6 months prior to malignancy diagnosis, an increased HR of CMV-related infections, adjusting for congenital malformations, deformations, and chromosome abnormalities, was detected for hematologic malignancies [HR, 11.2; 95% confidence interval (CI), 5.8-21.5], but not for central nervous system tumors.

CONCLUSIONS

Higher CMV incidence was detected for children ostensibly exposed through maternal CMV infection during pregnancy with the index child.

IMPACT

The data are compatible with a congenital infection of CMV leading to increased risk of childhood hematologic malignancies, but not tumors of the central nervous system, although a cautious interpretation is warranted because of the small numbers.

The emerging story of acute lymphoblastic leukemia among the Latin American population - biological and clinical implications

Higher incidence rates and poor outcomes have been reported among Latin American patients (Latinos) with acute lymphoblastic leukemia (ALL). Distinct patterns in recent genomic studies allude to a predisposing genetic component. In this review, we critically examine the increasing amount of empirical information on the epidemiology, outcomes and genomics of Latinos with ALL. We discuss the immense diversity within the Latino community and varying definitions of what is considered Latino, which pose an epidemiological challenge. Environmental factors have been evaluated as possible predisposing factors in the development of ALL but studies have produced conflicting results. In this review we describe chromosomal abnormalities and the specific genomic landscape in Latinos with ALL and their association with unfavorable prognosis, focusing on the higher frequency of Philadelphia chromosome-Like ALL. Recent data suggest an association between polymorphisms that are commonly found in indigenous Americans and high rates of ALL. The review compares the distribution of ALL throughout the various countries in Latin America in an attempt to shed some epidemiological light on the genetic ancestry of ALL. We additionally identify areas where research is warranted in efforts toward the advent of novel targeted agents that are relevant in improving outcomes within the Latino community.

A causal mechanism for childhood acute lymphoblastic leukaemia

In this Review, I present evidence supporting a multifactorial causation of childhood acute lymphoblastic leukaemia (ALL), a major subtype of paediatric cancer. ALL evolves in two discrete steps. First, in utero initiation by fusion gene formation or hyperdiploidy generates a covert, pre-leukaemic clone. Second, in a small fraction of these cases, the postnatal acquisition of secondary genetic changes (primarily V(D)J recombination-activating protein (RAG) and activation-induced cytidine deaminase (AID)-driven copy number alterations in the case of ETS translocation variant 6 (ETV6)-runt-related transcription factor 1 (RUNX1)+ ALL) drives conversion to overt leukaemia. Epidemiological and modelling studies endorse a dual role for common infections. Microbial exposures earlier in life are protective but, in their absence, later infections trigger the critical secondary mutations. Risk is further modified by inherited genetics, chance and, probably, diet. Childhood ALL can be viewed as a paradoxical consequence of progress in modern societies, where behavioural changes have restrained early microbial exposure. This engenders an evolutionary mismatch between historical adaptations of the immune system and contemporary lifestyles. Childhood ALL may be a preventable cancer.

Genetic polymorphisms of Th2 interleukins, history of asthma or eczema and childhood acute lymphoid leukaemia: Findings from the ESCALE study (SFCE)

BACKGROUND

Previous studies on the putative role of allergy in the aetiology of childhood leukaemia have reported contradictory results. The present study aimed to analyse the relation between a medical history of asthma or eczema and childhood acute lymphoid leukaemia (ALL) in light of potential candidate gene-environment interactions.

METHODS

Analyses were based on a subset of 434 cases of ALL and 442 controls successfully genotyped and of European ancestry children enrolled in a French population-based case-control study conducted in 2003-2004. Information about medical history was obtained during a standardized interview with the mothers. Candidate polymorphisms in genes of the Th2 cytokines IL4, IL10, IL13 and IL4-receptor, were genotyped or imputed.

RESULTS

None of the variant alleles were directly associated with childhood acute lymphoid leukaemia. A medical history of asthma or eczema was reported more often in the control group (OR = 0.7 [0.5-1.0]). This association was mostly seen in the group of children not carrying the IL13-rs20541 variant allele (Interaction Odds Ratio IOR 1.9, p-interaction = 0.07) and in those carrying the IL10 triple variant haplotype (IOR 0.5, p-interaction = 0.04). No interaction was observed with the candidate polymorphisms in IL4 and IL4R.

CONCLUSION

This study provides a new insight into the relationship between allergic symptoms and childhood acute lymphoid leukaemia, by suggesting this inverse association could be limited to children carrying certain genetic polymorphisms. If confirmed, these results could help better understand the biological mechanisms involved in the development of childhood acute lymphoid leukaemia.

Living on a farm, contact with farm animals and pets, and childhood acute lymphoblastic leukemia: pooled and meta-analyses from the Childhood Leukemia International Consortium

The associations between childhood acute lymphoblastic leukemia (ALL) and several factors related to early stimulation of the immune system, that is, farm residence and regular contacts with farm animals (livestock, poultry) or pets in early childhood, were investigated using data from 13 case-control studies participating in the Childhood Leukemia International Consortium. The sample included 7847 ALL cases and 11,667 controls aged 1-14 years. In all studies, the data were obtained from case and control parents using standardized questionnaires. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by unconditional logistic regression adjusted for age, sex, study, maternal education, and maternal age. Contact with livestock in the first year of life was inversely associated with ALL (OR = 0.65, 95% CI: 0.50, 0.85). Inverse associations were also observed for contact with dogs (OR = 0.92, 95% CI: 0.86, 0.99) and cats (OR = 0.87, 95% CI: 0.80, 0.94) in the first year of life. There was no evidence of a significant association with farm residence in the first year of life. The findings of these large pooled and meta-analyses add additional evidence to the hypothesis that regular contact with animals in early childhood is inversely associated with childhood ALL occurrence which is consistent with Greaves' delayed infection hypothesis.

An overview of disparities in childhood cancer: Report on the Inaugural Symposium on Childhood Cancer Health Disparities, Houston, Texas, 2016

The Inaugural Symposium on Childhood Cancer Health Disparities was held in Houston, Texas, on November 2, 2016. The symposium was attended by 109 scientists and clinicians from diverse disciplinary backgrounds with interests in pediatric cancer disparities and focused on reviewing our current knowledge of disparities in cancer risk and outcomes for select childhood cancers. Following a full day of topical sessions, everyone participated in a brainstorming session to develop a working strategy for the continued expansion of research in this area. This meeting was designed to serve as a springboard for examination of childhood cancer disparities from a more unified and systematic approach and to enhance awareness of this area of need.

GWAS in childhood acute lymphoblastic leukemia reveals novel genetic associations at chromosomes 17q12 and 8q24.21

Childhood acute lymphoblastic leukemia (ALL) (age 0-14 years) is 20% more common in Latino Americans than non-Latino whites. We conduct a genome-wide association study in a large sample of 3263 Californian children with ALL (including 1949 of Latino heritage) and 3506 controls matched on month and year of birth, sex, and ethnicity, and an additional 12,471 controls from the Kaiser Resource for Genetic Epidemiology Research on Aging Cohort. Replication of the strongest genetic associations is performed in two independent datasets from the Children's Oncology Group and the California Childhood Leukemia Study. Here we identify new risk loci on 17q12 near IKZF3/ZPBP2/GSDMB/ORMDL3, a locus encompassing a transcription factor important for lymphocyte development (IKZF3), and at an 8q24 region known for structural contacts with the MYC oncogene. These new risk loci may impact gene expression via local (four 17q12 genes) or long-range (8q24) interactions, affecting function of well-characterized hematopoietic and growth-regulation pathways.

Early vaccination protects against childhood leukemia: A systematic review and meta-analysis

Leukemia is the most commonly diagnosed childhood cancer, although its etiology is still largely unknown. Growing evidence supports a role for infection in the etiology of acute lymphocytic leukemia (ALL), and the involvement of the immune system suggests that vaccination may also play a role. However, the findings presented in the published literature are inconsistent. Therefore, we conducted a PRISMA systematic review and meta-analysis. 14 studies were identified and meta-analyzed. Vaccinations studied comprised Bacillus Calmette-Guérin (BCG) vaccine, Triple vaccine, Hepatitis B vaccine (HBV), Polio, Measles, Rubella, Mumps, trivalent MMR vaccine and Haemophilus influenza type B (HiB) vaccine. We observed a protective association between any vaccination in the first year of life and risk of childhood leukemia (summary odds ratio (OR) 0.58 [95% confidence interval (CI) 0.36-0.91]). When individual vaccines were analysed, some evidence of an association was seen only for BCG (summary OR 0.73 [95% CI 0.50-1.08]). In conclusion, early vaccination appears to be associated with a reduced risk of childhood leukemia. This finding may be underpinned by the association observed for BCG. Given the relatively imprecise nature of the results of this meta-analysis, our findings should be interpreted cautiously and replicated in future studies.

A systematic review and meta-analysis of the association between childhood infections and the risk of childhood acute lymphoblastic leukaemia

Background:

To determine whether childhood infections were associated with the development of childhood acute lymphoblastic leukaemia (ALL).

Methods:

We included studies that assessed any infection in childhood prior to the diagnosis of ALL in children aged 0–19 years compared to children without cancer. The primary analysis synthesised any infection against the odds of ALL, and secondary analyses assessed the frequency, severity, timing of infections, and specific infectious agents against the odds of ALL. Subgroup analyses by data source were investigated.

Results:

In our primary analysis of 12 496 children with ALL and 2 356 288 children without ALL from 38 studies, we found that any infection was not associated with ALL (odds ratio (OR)=1.10, 95% CI: 0.95–1.28). Among studies with laboratory-confirmed infections, the presence of infections increased the odds of ALL by 2.4-fold (OR=2.42, 95% CI: 1.54–3.82). Frequency, severity, and timing of infection were not associated with ALL.

Conclusions:

The hypothesis put forward by Greaves and others about an infectious aetiology are neither confirmed nor refuted and the overall evidence remains inadequate for good judgement. The qualitative difference in the subgroup effects require further study, and future research will need to address the challenges in measuring infectious exposures.

IFN-γ directly inhibits murine B-cell precursor leukemia-initiating cell proliferation early in life

The early-life immune environment has been implicated as a modulator of acute lymphoblastic leukemia (ALL) development in children, with infection being associated with significant changes in ALL risk. Furthermore, polymorphisms in several cytokine genes, including IL-10 and IFN-γ, are associated with leukemia development. However, the mechanisms and timing of these influences remain unknown. Here, we use the Eμ-ret transgenic mouse model of B-cell precursor ALL to assess the influence of IFN-γ on the early-life burden of leukemia-initiating cells. The absence of IFN-γ activity resulted in greater numbers of leukemia-initiating cells early in life and was associated with accelerated leukemia onset. The leukemia-initiating cells from IFN-γ-knockout mice had reduced suppressor of cytokine signaling (SOCS-1) expression, were significantly more sensitive to IFN-γ, and exhibited more rapid expansion in vivo than their wild-type counterparts. However, sensitivity to this inhibitory pathway was lost in fully transformed IFN-γ-knockout leukemia cells. These results demonstrate that the influence of IFN-γ on ALL progression may not be mediated by selection of nascent transformed cells but rather through a general SOCS-mediated reduction in B-cell precursor proliferation. Thus, while cytokine levels may influence leukemia at multiple points during disease progression, our study indicates a significant early influence of basal, infection-independent cytokine production on leukemogenesis.

Trends in childhood leukemia incidence over two decades from 1992 to 2013

Incidence rates of childhood leukemia in the United States have steadily increased over the last several decades, but only recently have disparities in the increase in incidence been recognized. In the current analysis, Surveillance, Epidemiology and End Results (SEER) data were used to evaluate recent trends in the incidence of childhood leukemia diagnosed at age 0-19 years from 1992 to 2013, overall and by age, race/ethnicity, gender and histologic subtype. Hispanic White children were more likely than non-Hispanic White, non-Hispanic Black or non-Hispanic Asian children to be diagnosed with acute lymphocytic leukemia (ALL) from 2009 to 2013. From 1992 to 2013, a significant increase in ALL incidence was observed for Hispanic White children [annual percent change (APC)Hispanic  = 1.08, 95% CI: 0.59, 1.58]; no significant increase was observed for non-Hispanic White, Black or Asian children. ALL incidence increased by about 3% per year from 1992 to 2013 for Hispanic White children diagnosed from 15 to 19 years (APC = 2.67; 95% CI: 0.88, 4.49) and by 2% for those 10-14 years (APC = 2.09; 95% CI: 0.57, 3.63), while no significant increases in incidence were observed in non-Hispanic White, Black, or Asian children of the same age. Acute myeloid leukemia (AML) incidence increased among non-Hispanic White children under 1 year at diagnosis, and among Hispanic White children diagnosed at age 1-4. The increase in incidence rates of childhood ALL appears to be driven by rising rates in older Hispanic children (10-14, and 15-19 years). Future studies are needed to evaluate reasons for the increase in ALL among older Hispanic children.

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.

Pediatric T-cell acute lymphoblastic leukemia

The most common pediatric malignancy is acute lymphoblastic leukemia (ALL), of which T-cell ALL (T-ALL) comprises 10-15% of cases. T-ALL arises in the thymus from an immature thymocyte as a consequence of a stepwise accumulation of genetic and epigenetic aberrations. Crucial biological processes, such as differentiation, self-renewal capacity, proliferation, and apoptosis, are targeted and deranged by several types of neoplasia-associated genetic alteration, for example, translocations, deletions, and mutations of genes that code for proteins involved in signaling transduction, epigenetic regulation, and transcription. Epigenetically, T-ALL is characterized by gene expression changes caused by hypermethylation of tumor suppressor genes, histone modifications, and miRNA and lncRNA abnormalities. Although some genetic and gene expression patterns have been associated with certain clinical features, such as immunophenotypic subtype and outcome, none has of yet generally been implemented in clinical routine for treatment decisions. The recent advent of massive parallel sequencing technologies has dramatically increased our knowledge of the genetic blueprint of T-ALL, revealing numerous fusion genes as well as novel gene mutations. The challenges now are to integrate all genetic and epigenetic data into a coherent understanding of the pathogenesis of T-ALL and to translate the wealth of information gained in the last few years into clinical use in the form of improved risk stratification and targeted therapies. Here, we provide an overview of pediatric T-ALL with an emphasis on the acquired genetic alterations that result in this disease. © 2016 Wiley Periodicals, Inc.

Progress in Treatment of Viral Infections in Children with Acute Lymphoblastic Leukemia

In children, the most commonly encountered type of leukemia is acute lymphoblastic leukemia (ALL). An important source of morbidity and mortality in ALL are viral infections. Even though allogeneic transplantations, which are often applied also in ALL, carry a recognized risk for viral infections, there are multiple factors that make ALL patients susceptible to viral infections. The presence of those factors has an influence in the type and severity of infections. Currently available treatment options do not guarantee a positive outcome for every case of viral infection in ALL, without significant side effects. Side effects can have very serious consequences for the ALL patients, which include nephrotoxicity. For this reason a number of strategies for personalized intervention have been already clinically tested, and experimental approaches are being developed. Adoptive immunotherapy, which entails administration of ex vivo grown immune cells to a patient, is a promising approach in general, and for transplant recipients in particular. The ex vivo grown cells are aimed to strengthen the immune response to the virus that has been identified in the patients' blood and tissue samples. Even though many patients with weakened immune system can benefit from progress in novel approaches, a viral infection still poses a very significant risk for many patients. Therefore, preventive measures and supportive care are very important for ALL patients.

Caesarean delivery and risk of childhood leukaemia: a pooled analysis from the Childhood Leukemia International Consortium (CLIC)

BACKGROUND

Results from case-control studies have shown an increased risk of acute lymphoblastic leukaemia (ALL) in young children born by caesarean delivery, and prelabour caesarean delivery in particular; however, an association of method of delivery with childhood leukaemia subtypes has yet to be established. We therefore did a pooled analysis of data to investigate the association between childhood leukaemia and caesarean delivery.

METHODS

We pooled data from 13 case-control studies from the Childhood Leukemia International Consortium done in nine countries (Canada, Costa Rica, Egypt, France, Germany, Greece, Italy, New Zealand, and the USA) for births from 1970-2013. We analysed caesarean delivery overall and by indications that probably resulted in prelabour caesarean delivery or emergency caesarean delivery. We used multivariable logistic regression models, adjusted for child's birthweight, sex, age, ethnic origin, parental education, maternal age, and study, to estimate odds ratios (ORs) and 95% CIs for the risk of ALL and acute myeloid leukaemia (AML) in children aged 0-14 years at diagnosis.

FINDINGS

The studies provided data for 8780 ALL cases, 1332 AML cases, and 23 459 controls, of which the birth delivery method was known for 8655 (99%) ALL cases, 1292 (97%) AML cases, and 23 351 (>99%) controls. Indications for caesarean delivery were available in four studies (there were caesarean deliveries for 1061 of 4313 ALL cases, 138 of 664 AML cases, and 1401 of 5884 controls). The OR for all indications of caesarean delivery and ALL was 1·06 (95% CI 0·99-1·13), and was significant for prelabour caesarean delivery and ALL (1·23 [1·04-1·47]; p=0·018). Emergency caesarean delivery was not associated with ALL (OR 1·02 [95% CI 0·81-1·30]). AML was not associated with caesarean delivery (all indications OR 0·99 [95% CI 0·84-1·17]; prelabour caesarean delivery 0·83 [0·54-1·26]; and emergency caesarean delivery 1·05 [0·63-1·77]).

INTERPRETATION

Our results suggest an increased risk of childhood ALL after prelabour caesarean delivery. If this association is causal, maladaptive immune activation due to an absence of stress response before birth in children born by prelabour caesarean delivery could be considered as a potential mechanism.

FUNDING

National Cancer Institute.

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

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