Epidemiological evidence for an infective basis in childhood leukaemia

Childhood B cell leukemia: Intercepting the paths to progression

B-cell Acute Lymphoblastic Leukemia (B-ALL) is the most common pediatric cancer, arising most often in children aged 2-5 years. This distinctive age distribution hints at an association between B-ALL development and disrupted immune system function during a susceptible period during childhood, possibly triggered by early exposure to infection. While cure rates for childhood B-ALL surpass 90% in high-income nations, survivors suffer from diminished quality of life due to the side effects of treatment. Consequently, understanding the origins and evolution of B-ALL, and how to prevent this prevalent childhood cancer, is paramount to alleviate this substantial health burden. This article provides an overview of our current understanding of the etiology of childhood B-ALL and explores how this knowledge can inform preventive strategies.

Breastfeeding Duration Reduces the Risk of Childhood Leukemia and Modifies the Risk of Developing Functional Gastrointestinal Disorders

Objective: The aim of this study was to test the hypothesis that the duration of breastfeeding in infancy reduces the risk of childhood leukemia or lymphoma, and modifies the risk of developing functional gastrointestinal disorders (FGIDs). Subjects and Methods: This case-control study involved the recruitment of children with lymphoid malignancy and functional gastrointestinal symptoms with healthy children as controls. Focused questionnaires were used to collect data on breastfeeding history and other key risk factors. Univariate and multivariate analyses were undertaken. Results: Of the 334 children with lymphoid malignancy, 65% were male. The control group included 334 age- and sex-matched participants. Most (n = 189; 56.6%) of the children with leukemia were <10 years of age. Differences between cases and controls included the duration of breastfeeding (p < 0.0001), mean birthweight (p < 0.001), maternal age (p < 0.001), paternal age (p < 0.001), birth order (p < 0.001), mean number of children (p < 0.001), BMI percentile (p = 0.042), and maternal smoking (p = 0.012). Breastfeeding duration of up to 6 months' duration, when compared with feeding of longer than 6 months, was associated with increased odds ratios (OR) for acute lymphoblastic leukemia (OR = 3.43, 95% confidence interval [CI] 2.37-4.98; p < 0.001), Hodgkin's lymphoma (OR = 1.58, 95% CI: 0.88-2.84, p = 0.120), Non-Hodgkin's lymphoma (OR = 2.14, 95% CI: 1.25-3.65, p = 0.005), and overall (OR = 1.95, 95% CI: 1.40-2.71, p < 0.001). Cases also differed from controls with regard to FGIDs, such as stomach ache (p < 0.001), dyspepsia (p < 0.001), early satiety (p = 0.017), bowel satisfaction (p < 0.001), bloating (p < 0.001), nausea (p = 0.005), vomiting (p = 0.039), constipation (p = 0.003), diarrhea (p = 0.010), gastrointestinal canal congestion (p =0.039), muscle aches pains (p = 0.008), fecal incontinence (p = 0.021), and indigestion (p = 0.003). A multivariate stepwise regression analysis revealed that maternal smoking (p < 0.001), formula feeding (p < 0.001), duration of breastfeeding (p < 0.001), birth order (p = 0.002), mother's age (p = 0.004) and the child's birthweight (p = 0.009) were predictors for leukemia. Further analysis showed that dyspepsia (p < 0.001), gastrointestinal tract canal congestion (p < 0.001), constipation (p = 0.009), diarrhea (p = 0.013), bowel satisfaction (p = 0.021), bloating (p = 0.022), duration of breastfeeding (p < 0.001), and stomach ache (p = 0.025) were significant predictors for developing FGID symptoms after adjusting for age, gender, and other confounding variables. Conclusion: This study confirmed that breastfeeding has some effect on reducing possible risk of childhood lymphoma and leukemia and FGID symptoms compared with healthy control children.

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.

Evaluation of the Association Between Congenital Cytomegalovirus Infection and Pediatric Acute Lymphoblastic Leukemia

IMPORTANCE

Acute lymphoblastic leukemia (ALL) is the most common form of pediatric cancer, and a leading cause of death in children. Understanding the causes of pediatric ALL is necessary to enable early detection and prevention; congenital cytomegalovirus (cCMV) has recently been identified as a potential moderate-to-strong factor associated with risk for ALL.

OBJECTIVE

To compare the prevalence of cCMV infection between ALL cases and matched controls.

DESIGN, SETTING, AND PARTICIPANTS

In this population-based case-control study of ALL cases and matched controls, cases consisted of children aged 0 to 14 years between 1987 and 2014 with an ALL diagnosis identified through the Michigan Cancer Surveillance Program and born in Michigan on or after October 1, 1987. Cancer-free controls were identified by the Michigan BioTrust for Health and matched on age, sex, and mother's race and ethnicity. Data were analyzed from November to May 2022.

EXPOSURES

cCMV infection measured by quantitative polymerase chain reaction in newborn dried blood spots.

MAIN OUTCOMES AND MEASURES

ALL diagnosed in children aged 0 to 14 years.

RESULTS

A total of 1189 ALL cases and 4756 matched controls were included in the study. Bloodspots were collected from participants at birth, and 3425 (57.6%) participants were male. cCMV was detected in 6 ALL cases (0.5%) and 21 controls (0.4%). There was no difference in the odds of cCMV infection comparing ALL cases with controls (odds ratio, 1.30; 95% CI, 0.52-3.24). Immunophenotype was available for 536 cases (45.1%) and cytogenetic data for 127 (27%). When stratified by subtype characteristics, hyperdiploid ALL (74 cases) was associated with 6.26 times greater odds of cCMV infection compared with unmatched controls (95% CI, 1.44-27.19).

CONCLUSIONS AND RELEVANCE

In this case-control study of cCMV and pediatric ALL, cCMV was associated with increased risk of hyperdiploid ALL. These findings encourage continued research.

Bimodal Age Distribution in Cancer Incidence

Cancer is caused by accumulation of genetic changes which include activation of protooncogenes and loss of tumor suppressor genes. The age-specific incidence of cancer in general increases with advancing age. However, some cancers exhibit a bimodal distribution. Commonly recognized cancers with bimodal age distribution include acute lymphoblastic leukemia, osteosarcoma, Hodgkin's lymphoma, germ cell tumors and breast cancer. Delayed infection hypothesis has been used to provide explanation for the early childhood peak in leukemias and lymphomas, whereas the peak at an older age is associated with accumulation of protooncogenes and weakened immune system. Further genetic analysis and histopathological variations point to distinctly different cancers, varying genetically and histologically, which are often combined under a single category of cancers. Tumor characteristics and age distribution of these cancers varies also by population groups and has further implications on cancer screening methods. Although significant advances have been made to explain the bimodal nature of such cancers, the specific genetic mechanisms for each age distribution remain to be elucidated. Further distinction among the different cancer subtypes may lead to improvements in individual risk assessments, prevention and enhancement of treatment strategies.

Identification of seasonal variation in the diagnosis of acute myeloid leukaemia: a population-based study

Until now, the role that seasonal factors play in the aetiology of acute myeloid leukaemia (AML) has been unclear. Demonstration of seasonality in AML diagnosis would provide supportive evidence of an underlying seasonal aetiology. To investigate the potential seasonal and long‐term trends in AML diagnosis in an overall population and in subgroups according to sex and age, we used population‐based data from a Spanish hospital discharge registry. We conducted a larger study than any to date of 26 472 cases of AML diagnosed in Spain between 2004 and 2015. Using multivariable Poisson generalized linear autoregressive moving average modelling, we found an upward long‐term trend, with monthly incidence rates of AML annually increasing by 0.4% [95% confidence interval (CI), 0.2%–0.6%; p = 0.0011]. January displayed the highest incidence rate of AML, with a minimum average difference of 7% when compared to February (95% CI, 2%–12%; p = 0.0143) and a maximum average difference of 16% compared to November (95% CI, 11%–21%; p < 0.0001) and August (95% CI, 10%–21%; p < 0.0001). Such seasonal effect was consistent among subgroups according to sex and age. Our finding that AML diagnosis is seasonal strongly implies that seasonal factors, such as infectious agents or environmental triggers, influence the development and/or proliferation of disease, pointing to prevention opportunities.

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.

Childhood leukemia near nuclear sites in Belgium: An ecological study at small geographical level

BACKGROUND

A previous investigation of the occurrence of childhood acute leukemia around the Belgian nuclear sites has shown positive associations around one nuclear site (Mol-Dessel). In the following years, the Belgian Cancer Registry has made data available at the smallest administrative unit for which demographic information exists in Belgium, i.e. the statistical sector. This offers the advantage to reduce the potential misclassification due to large geographical scales.

METHODS

The current study performed for the period 2006-2016 uses Poisson models to investigate (i) the incidence of childhood acute leukemia within 20 km around the four Belgian nuclear sites, (ii) exposure-response relationships between cancer incidence and surrogate exposures from the nuclear sites (distance, wind direction frequency and exposure by hypothetical radioactive discharges taking into account historical meteorological conditions). All analyses are carried out at statistical sector level.

RESULTS

Higher incidence rate ratios were found for children <15 years (7 cases, RR = 3.01, 95% CI: 1.43;6.35) and children <5 years (< 5 cases, RR = 3.62, 95% CI: 1.35;9.74) living less than 5 km from the site of Mol-Dessel. In addition, there was an indication for positive exposure-response relationships with the different types of surrogate exposures.

CONCLUSION

Results confirm an increased incidence of acute childhood leukemia around Mol-Dessel, but the number of cases remains very small. Random variation cannot be excluded and the ecological design does not allow concluding on causality. These findings emphasize the need for more in-depth research into the risk factors of childhood leukemia, for a better understanding of the etiology of this disease.

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.

Acute lymphoid leukemia etiopathogenesis

Acute lymphoid leukemia (ALL) is a type of hematological neoplasm that affects the precursor cells of strains B, T  and NK, with a higher incidence in the pediatric range. The pathophysiology of ALL is characterized by chromosomal abnormalities and genetic alterations involved in the differentiation and proliferation of lymphoid precursor cells. Despite the lack of information in the literature, it is believed that leukemogenesis originates from a complex interaction between environmental and genetic factors, which combined lead to cellular modifications. Environmental factors have been evaluated as possible predisposing factors in the development of ALL but there are still conflicting results in the world literature. In this context, the aim of the present review is to discuss the major exogenous factors regarding ALL.

Apparent difference in fatalities between Central Europe and East Asia due to SARS-COV-2 and COVID-19: Four hypotheses for possible explanation

The comparison of the numbers of cases and deaths due to SARS-CoV-2/COVID-19 shows that people in Central Europe are much more affected than people in East Asia where the disease originally occurred. Trying to explain this difference, this communication presents four hypotheses that propose the following reasons for the observed findings: 1) Differences in social behaviors and cultures of people in the two regions; 2) Possible outbreak of virulent viruses in Central Europe due to multiple viral infection, and the involvement of immuno-virological factors associated with it, 3) Possibility of corona resistance gene mutation occurring among East Asians as a result of long-term co-evolution of virus and host, and 4) possible involvement of hygienic factors. Direct or indirect supportive evidences for each one of our hypotheses are presented and experimental approaches for their evaluation are discussed. Finally, we suggest that the dynamics of the pandemic also shows that the problems of the new coronavirus can be overcome due to people's awareness of the epidemics, rational viral diagnostics and a high level of medical care.

The Likelihood of Adverse Pregnancy Outcomes and Genetic Disease (Transgenerational Effects) from Exposure to Radioactive Fallout from the 1945 Trinity Atomic Bomb Test

The potential health consequences of the Trinity nuclear weapon test of 16 July 1945 at Alamogordo, New Mexico, are challenging to assess. Population data are available for mortality but not for cancer incidence for New Mexico residents for the first 25 y after the test, and the estimates of radiation dose to the nearby population are lower than the cumulative dose received from ubiquitous natural background radiation. Despite the estimates of low population exposures, it is believed by some that cancer rates in counties near the Trinity test site (located in Socorro County) are elevated compared with other locations across the state. Further, there is a concern about adverse pregnancy outcomes and genetic diseases (transgenerational or heritable effects) related to population exposure to fallout radiation. The possibility of an intergenerational effect has long been a concern of exposed populations, e.g., Japanese atomic bomb survivors, survivors of childhood and adolescent cancer, radiation workers, and environmentally exposed groups. In this paper, the likelihood of discernible transgenerational effects is discounted because (1) in all large-scale comprehensive studies of exposed populations, no heritable genetic effects have been demonstrated in children of exposed parents; (2) the distribution of estimated doses from Trinity is much lower than in other studied populations where no transgenerational effects have been observed; and (3) there is no evidence of increased cancer rates among the scientific, military, and professional participants at the Trinity test and at other nuclear weapons tests who received much higher doses than New Mexico residents living downwind of the Trinity site.

Early immune stimulation and childhood acute lymphoblastic leukemia in Costa Rica: A comparison of statistical approaches

BACKGROUND

Although epidemiologic studies suggest that early immune stimulation is protective against childhood leukemia, evidence for this relationship is equivocal for Hispanic children, who are disproportionately affected by this disease. The complex biological processes underlying immune stimulation and leukemogenesis may benefit from novel statistical approaches that account for mixed exposures and their nonlinear interactions. In this study, we utilized targeted machine learning and traditional statistical methods to investigate the association of multiple measures of early immune stimulation with acute lymphoblastic leukemia (ALL) in Costa Rican children.

MATERIALS AND METHODS

We used data from a population-based case-control study conducted in Costa Rica (2001-2003). Cases of ALL (n = 240) were diagnosed in 1995-2000 (age >1 year and <15 years at diagnosis) and were identified through the National Cancer Registry and National Children's Hospital. Population controls (n = 578) were frequency-matched to cases by birth year and drawn from the National Birth Registry. Data on surrogate measures of early immune stimulation were collected through in-home interviews. We fitted multivariable models, utilizing targeted causal inference (varimpact), unconditional logistic regression, and latent class analysis (LCA).

RESULTS

In varimpact analysis, contact with any pet [risk difference (RD) = -0.17, 95% CI: -0.25, -0.10)] or any farm animal (RD = -0.07, 95% CI: -0.13, 0.00) and allergies (RD = -0.08, 95% CI: -0.17, 0.01) were associated with a reduced risk of ALL, whereas experiencing a fever longer than one week was associated with an increased risk (RD = 0.23, 95% CI: 0.12, 0.33). In unconditional logistic regression models, contact with any pet or farm animal and a complete vaccination scheme were inversely associated with odds of ALL (OR = 0.44, 95% CI: 0.31, 0.62; OR = 0.66, 95% CI: 0.49, 0.90; OR = 0.45, 95% CI: 0.24, 0.83; respectively), whereas experiencing a fever longer than one week was positively associated with ALL (OR = 2.44, 95% CI: 1.61, 3.70). Two-class and three-class LCA revealed a group with elevated risk for ALL whose exposure profile was mainly characterized by reduced exposure to pets and farm animals.

CONCLUSIONS

Using distinct statistical approaches, we observed that exposure to pets and farm animals was inversely associated with ALL risk, whereas having a fever longer than one week (a putative proxy of severe infection) was associated with an increased risk. For multifactorial diseases such as childhood leukemia, we recommend estimating the joint effects of multiple exposures by applying diverse statistical methods and interpreting their results together. Overall, we found support for the hypothesis that early immune stimulation offers protection against childhood ALL.

Childhood leukaemia incidence and trends in a Middle Eastern country during 1980-2014: a population-based study

BACKGROUND

This retrospective cohort study examines the trends in childhood leukaemia age-standardized incidence rates (ASIRs) (per million person-years) using cases which were diagnosed at age 0-19 years from 1980 to 2014 and recorded in the Kuwait Cancer Control Center (KCCC) registry.

METHODS

Childhood leukaemia age-specific incidence rates overall and by sub-cohorts defined by age (0-4, 5-9, 10-14, and 15-19 years), sex (male, female) and nationality (Kuwaiti, non-Kuwaiti) were computed and age-standardized. Joinpoint regression models were used to evaluate trends in childhood leukaemia ASIRs. Average annual percent change (AAPC) and its 95% confidence interval (CI) were used to interpret the observed trends.

RESULTS

During the study period, 1077 childhood leukaemia cases of 32.3 million person-years were diagnosed. From 1980 to 2014, the average annual childhood leukaemia ASIR was 53.1 (95% CI 20.9, 85.2). Overall childhood leukaemia ASIRs significantly decreased on average by 6.8% per year (AAPC =  -6.8; 95% CI -12.1, -1.1; p = 0.02) from 1980 to 1993, but a marginally significant increase in ASIRs from 1993 to 2014 was recorded (AAPC = 2.5; 95% CI -0.5, 5.5; p = 0.10). During the entire period, childhood leukaemia ASIRs trends significantly (p < 0.05) increased among 6 of 16 sub-cohorts, which was more pronounced among females and 10-14-year-old children.

CONCLUSIONS

Overall, ASIRs significantly increased from 1993 to 2014, which specifically seems to be driven by an increase in ASIRs among females and 10-14 -year-old children. These increasing trends underscore the potential involvement of a range of exposures. Future studies on unravelling such factors may help develop preventive measures to minimize childhood leukaemia risk in this and similar settings in the region.

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.

Socioeconomic status and incidence of pediatric leukemia in Canada: 1992-2010

BACKGROUND

Leukemia is the most common cancer among Canadian children, representing about a third of pediatric cancers in Canada and is responsible for about one-third of pediatric cancer deaths. Understanding the effect of socioeconomic status (SES) on pediatric leukemia incidence provides valuable information for cancer control and interventions in Canada.

METHODS

Using a linked data from the Canadian Cancer Registry (CCR), Canadian Census of Population (CCP) and National Household Survey (NHS) we aimed to quantify socioeconomic inequalities in the incidence of pediatric leukemia from 1992 to 2010. We used the concentration index (C) approach to quantify income- and education-related inequalities in the incidence of pediatric leukemia over time.

RESULTS

Though there were fluctuations in incidence over the study period, our results showed that the total incidence of pediatric leukemia in Canada was generally consistent from 1992 to 2010. Incidence rate of 47 per 1,000,000 as at 1992 rose to 57 per 1,000,000 in 2010. The estimated values of the C over the study period failed to show any significant association between pediatric leukemia incidence and household income or education status.

CONCLUSIONS

Although pediatric leukemia incidence is not rising significantly, it is not reducing significantly either. The incidence of pediatric leukemia showed no significant association with socioeconomic status. Future cancer control interventions should focus more on mitigating risk factors that are independent of socioeconomic status.

Ionising radiation and childhood leukaemia revisited

Increased incidences of childhood acute leukaemia were noted among survivors of the atomic bombings of Hiroshima and Nagasaki. In Western societies, Childhood Acute Lymphoblastic Leukaemia has a distinct epidemiology peaking at 3 years old. Exposure to ionising radiation is an established hazard but it is difficult to gauge the precise risk of less than 100 mSv. Since 1983 significant leukaemia incidences have been reported among families residing near nuclear installations. The target cells (naïve neonatal lymphocytes) get exposed to multiple xenobiotic challenges and undergo extraordinary proliferation and physiological somatic genetic change. Population movements and ionising radiation are considered taking account of updated understanding of radiation biology, cancer cytogenetics and immunological diversity. Double Strand Breaks in DNA arise through metabolic generation of Reactive Oxygen Species, and nearly always are repaired; but mis-repairs can be oncogenic. Recombinant Activating Gene enzymes in rapidly dividing perinatal pre-B lymphocytes being primed for antibody diversity are targeted to Signal Sequences in the Immunoglobulin genes. off target pseudo-sequences may allow RAG enzymes to create autosomal DSBs which, when mis-repaired, become translocated oncogenes. Immunogens acting by chance at crucial stages may facilitate this. In such circumstances, oncogenic DSBs from ionising radiation are less likely to be significant.

Can legal restrictions of prenatal exposure to industrial trans-fatty acids reduce risk of childhood hematopoietic neoplasms? A population-based study

BACKGROUND

Causes of most childhood hematopoietic neoplasms are unknown. Early age of occurrence suggests prenatal etiology. Positive associations have been reported between industrially produced trans-fatty acids (iTFAs) and risks of some cancers in adults. iTFAs are pro-inflammatory and adversely affect the beneficial effects of essential fatty acids, the latter is diminishing tumor growth. In 2004 Denmark legislated against the use of iTFA in foodstuffs. Using the entire population, we investigated if the changes in the legislation as a proxy to the reduced exposure to iTFA had affected the incidence of childhood hematopoietic neoplasms.

METHODS

We used a Cox proportional hazard model to compare the hazard of childhood hematopoietic neoplasms among children born before and after the iTFA ban, as a proxy for fetal iTFA exposure. To take the potential secular trend in hematopoietic neoplasms into account, we modeled the variation in cancer risk across birth cohorts by a piecewise linear spline with a knot in 2004, which allowed a comparison of the hazard of childhood hematopoietic neoplasms between the time before and after the iTFA ban.

RESULTS

Among children born in 1988-2008 in Denmark, 720 were diagnosed with hematopoietic neoplasms before the age of 7 years, corresponding to an overall incidence rate of 7.6 per 100 000 person years. The incidence rates increased by 2% per cohort in 1988-2004 (hazard ratio: 1.02 [1.01; 1.04]) and in 2004-2008 (hazard ratio: 1.02 [0.95; 1.11]).

CONCLUSIONS

No apparent benefit of the iTFA legislation in reducing childhood hematopoietic neoplasms was observed on population basis. Individual-level data are needed to investigate any possible associations between biomarkers of iTFA intake and risk of childhood hematopoietic neoplasms.

Childhood cancer research in oxford III: The work of CCRG on ionising radiation

BACKGROUND

High doses of ionising radiation are a known cause of childhood cancer and great public and professional interest attaches to possible links between childhood cancer and lower doses, particularly of man-made radiation. This paper describes work done by the Childhood Cancer Research Group (CCRG) on this topic METHODS: Most UK investigations have made use of the National Registry of Childhood Tumours and associated controls. Epidemiological investigations have included national incidence and mortality analyses, geographical investigations, record linkage and case-control studies. Dosimetric studies use biokinetic and dosimetric modelling.

RESULTS

This paper reviews the work of the CCRG on the association between exposure to ionising radiation and childhood cancer, 1975-2014.

CONCLUSION

The work of CCRG has been influential in developing understanding of the causes of 'clusters' of childhood cancer and the risks arising from exposure to ionising radiation both natural and man-made. Some clusters around nuclear installations have certainly been observed, but ionising radiation does not seem to be a plausible cause. The group's work has also been instrumental in discounting the hypothesis that paternal preconception irradiation was a cause of childhood cancers and has demonstrated an increased leukaemia risk for children exposed to higher levels of natural gamma-ray radiation.

Failed Vacuum and the Long-term Hematologic Morbidity of the Offspring

OBJECTIVE

We aimed to investigate the effect of failed vacuum delivery leading to an emergency cesarean delivery on the long-term pediatric hematologic morbidity of the offspring.

STUDY DESIGN

In this population-based cohort study, the risk of long-term hematologic morbidity (up to the age of 18 y) was evaluated in children born following successful vacuum vaginal delivery, as compared with that of children born following a failed procedure leading to an emergent cesarean delivery. Multiple pregnancies and fetuses with congenital malformations were excluded. A Kaplan-Meier survival curve was constructed to compare cumulative pediatric hematologic morbidity, and a Cox proportional hazards model was used to control for confounders.

RESULTS

A total of 7978 neonates met the inclusion criteria. Vacuum delivery was successful in 7733 cases (96.9%), whereas it failed in 245 cases (3.1%). Total hematologic morbidity of the offspring up to 18 years of age was comparable between the groups (1.6% vs. 0.8%, P=0.8). The Kaplan-Meier survival curve showed no difference in the cumulative incidence of total hematologic morbidity (log rank, P=0.22). In the Cox regression model, failed vacuum delivery was not independently associated with long-term hematologic morbidity, as compared with a successful procedure, while adjusting for multiple confounders (adjusted hazards ratio [HR], 1.8; 95% confidence interval, 0.7-5.0; P=0.25).

CONCLUSIONS

Failed vacuum delivery does not seem to be associated with an increased risk for pediatric hematologic morbidity of the offspring up to 18 years of age.

The influence of prenatal exposure to trans-fatty acids for development of childhood haematopoietic neoplasms (EnTrance): a natural societal experiment and a case-control study

BACKGROUND

Little is known about the causes of childhood cancer, partly as not many children develop cancer, although childhood cancer is a leading cause of death by disease in the young. The young age of the children suggests that risk factors for childhood cancer may be present during pregnancy. Previous studies have shown that exposure to trans-fat, a type of unsaturated fat common in industrially produced foods (iTFA), has adverse health effects in adults, including the risk of developing cancer. Haematopoietic neoplasms are the most common cancer types among European children under the age of 15 years. This study will bring new knowledge as to whether trans-fat and other fatty acids may also increase the risk of developing haematopoietic neoplasms during childhood.

METHODS

We will investigate if the Danish iTFA legislation ban, which radically reduced the use of iTFA in foodstuffs, influenced the risk of childhood haematopoietic neoplasms in children born either before or after the change in legislation, adjusting for relevant secular trends. Further, in a case-control study, we will examine if levels of fatty acids in dried blood spots from newborns can predict the risk of developing childhood haematopoietic neoplasms. Permission from the Danish Data Protection Agency and the Ethical Committee has been granted.

DISCUSSION

The results from this study will provide important information about fatty acids in the mother's diet as a contributor to development of haematopoietic neoplasms during childhood, which may result in relevant preventive action.

TRIAL REGISTRATION

Not relevant.

Can changes in population mixing and socio-economic deprivation in Cumbria, England explain changes in cancer incidence around Sellafield?

Previously excesses in incident cases of leukaemia and non-Hodgkin lymphoma have been observed amongst young people born or resident in Seascale, Cumbria. These excesses have not been seen more recently. It is postulated that the former apparent increased risk was related to 'unusual population mixing', which is not present in recent years. This study investigated changes in measures of population mixing from 1951-2001. Comparisons were made between three specified areas. Area-based measures were calculated (migration, commuting, deprivation, population density). All areas have become more affluent, although Seascale was consistently the most affluent. Seascale has become less densely populated, with less migration into the ward and less diversity with respect to migrants' origin. There have been marked changes in patterns of population mixing throughout Cumbria. Lesser population mixing has been observed in Seascale in recent decades. Changes in pattern and nature of population mixing may explain the lack of recent excesses.

Pediatric precursor B acute lymphoblastic leukemia: are T helper cells the missing link in the infectious etiology theory?

Precursor B acute lymphoblastic leukemia (BCP-ALL), the most common childhood malignancy, arises from an expansion of malignant B cell precursors in the bone marrow. Epidemiological studies suggest that infections or immune responses to infections may promote such an expansion and thus BCP-ALL development. Nevertheless, a specific pathogen responsible for this process has not been identified. BCP-ALL cells critically depend on interactions with the bone marrow microenvironment. The bone marrow is also home to memory T helper (Th) cells that have previously expanded during an immune response in the periphery. In secondary lymphoid organs, Th cells can interact with malignant cells of mature B cell origin, while such interactions between Th cells and malignant immature B cell in the bone marrow have not been described yet. Nevertheless, literature supports a model where Th cells—expanded during an infection in early childhood—migrate to the bone marrow and support BCP-ALL cells as they support normal B cells. Further research is required to mechanistically confirm this model and to elucidate the interaction pathways between leukemia cells and cells of the tumor microenvironment. As benefit, targeting these interactions could be included in current treatment regimens to increase therapeutic efficiency and to reduce relapses.

Home remodeling and risk of childhood leukemia

PURPOSE

We investigated the relationship between the risk of childhood leukemia and home remodeling, a surrogate for indoor chemical exposures.

METHODS

We collected information on remodeling activities carried out between birth and diagnosis in homes of 609 acute lymphoblastic leukemia (ALL) cases, 89 acute myeloid leukemia (AML) cases, and 893 matched controls participating in the California Childhood Leukemia Study (1995-2008). We used multivariable logistic regression to estimate the risk of ALL and AML associated with six remodeling activities: construction, painting, recarpeting, reflooring, roofing, and weatherproofing. Models were adjusted for age, sex, Hispanic ethnicity, race, household annual income, and residential mobility.

RESULTS

Construction in the home between birth and diagnosis was associated with a significant increase in ALL risk (odds ratio [OR]: 1.52, 95% confidence interval [CI]: 1.14-2.02) and a nonsignificant increase in AML risk (OR: 1.75, 95% CI: 0.98-3.15). No other remodeling activities were associated with ALL or AML risk in the main analysis. When stratifying by Hispanic ethnicity, a positive relationship between ALL risk and painting was evident in Hispanic children (OR: 1.47, 95% CI: 1.04-2.07).

CONCLUSIONS

Specific home remodeling activities appeared to be associated with increased risk of childhood ALL.

Animal Models for the Study of Childhood Leukemia: Considerations for Model Identification and Optimization to Identify Potential Risk Factors

Leukemias are the most common pediatric malignancies diagnosed in western industrialized societies. In spite of the substantial incidence of childhood leukemia in the United States and other countries, neither epidemiology studies conducted in human populations nor hazard identification studies conducted using traditional animal models have identified environmental or other factors that are directly linked to increased risk of disease. Molecular biology data and mathematical modeling of incidence patterns suggest that pediatric leukemogenesis may occur through a multistage or “multihit” mechanism that involves both in utero and postnatal events. The authors propose that pediatric leukemias can be modeled experimentally using a “multihit” paradigm analogous to the “initiation-promotion” and “complete carcinogenesis” models developed for tumor induction in mouse skin and rat liver. In this model for childhood leukemia, an initial genetic alteration occurs during in utero or early postnatal development, but clinical disease develops only upon additional genetic or nongenetic events that occur during the postnatal period. Application of this multistage or “multihit” model to hazard assessment studies conducted in transgenic or knockout mice carrying relevant molecular lesions may provide a sensitive approach to the identification of environmental agents that are important risk factors for childhood leukemia.

Childhood Leukemia and Primary Prevention

Leukemia is the most common pediatric cancer, affecting 3800 children per year in the United States. Its annual incidence has increased over the last decades, especially among Latinos. Although most children diagnosed with leukemia are now cured, many suffer long-term complications, and primary prevention efforts are urgently needed. The early onset of leukemia-usually before 5 years of age-and the presence at birth of "pre-leukemic" genetic signatures indicate that pre- and postnatal events are critical to the development of the disease. In contrast to most pediatric cancers, there is a growing body of literature-in the United States and internationally-that has implicated several environmental, infectious, and dietary risk factors in the etiology of childhood leukemia, mainly for acute lymphoblastic leukemia, the most common subtype. For example, exposures to pesticides, tobacco smoke, solvents, and traffic emissions have consistently demonstrated positive associations with the risk of developing childhood leukemia. In contrast, intake of vitamins and folate supplementation during the preconception period or pregnancy, breastfeeding, and exposure to routine childhood infections have been shown to reduce the risk of childhood leukemia. Some children may be especially vulnerable to these risk factors, as demonstrated by a disproportionate burden of childhood leukemia in the Latino population of California. The evidence supporting the associations between childhood leukemia and its risk factors-including pooled analyses from around the world and systematic reviews-is strong; however, the dissemination of this knowledge to clinicians has been limited. To protect children's health, it is prudent to initiate programs designed to alter exposure to well-established leukemia risk factors rather than to suspend judgment until no uncertainty remains. Primary prevention programs for childhood leukemia would also result in the significant co-benefits of reductions in other adverse health outcomes that are common in children, such as detriments to neurocognitive development.

Epidemiological study of power lines and childhood cancer in the UK: further analyses

We report further analyses from an epidemiological study of childhood cancer and residence at birth near high-voltage power lines in the UK. These results suggest that the elevated risks for childhood leukaemia that we previously found for overhead power lines may be higher for older age at diagnosis and for myeloid rather than lymphoid leukaemia. There are differences across regions of birth but not forming any obvious pattern. Our results suggest the decline in risk we previously reported from the 1960s to the 2000s is linked to calendar year of birth or of cancer occurrence rather than the age of the power lines concerned. Finally, we update our previous analysis of magnetic fields to include later subjects.

Specific and Non-specific Clinical Presentations in the Year Before the Diagnosis of Childhood Leukaemia

INTRODUCTION

Clinical presentations of childhood leukaemia have been reported in case-only studies. The timing when these presentations start to occur prior to diagnosis is less clear.

METHODS

In this nested case-control study, 1,025 and 334 children with lymphoid and myeloid leukaemia, respectively, were matched (1:30) to population-based controls by sex, region and year of birth. An index date was assigned for each control when the matched case was diagnosed. Healthcare access records of cases and controls in the year before the index date were extracted.

RESULTS

Children with lymphoid leukaemia started to visit doctors more often at least 2 months before leukaemia diagnosis (P < 0.05). Various presentations were recorded in these visits: rates of haematological presentations, musculoskeletal presentations, and injuries started to increase significantly at least 3 months before diagnosis; rates of respiratory, gastrointestinal and urinary tract presentations did not increase significantly until the last month. The findings for myeloid lymphoma were less clear, but children appeared to visit doctors more often at least 4 months before diagnosis, and the rate of haematological presentations also started to increase at least 4 months before leukaemia diagnosis. Although haematological presentations were most strongly associated with undiagnosed leukaemia (odds ratio > 290 in the last month), the majority (>96%) of children with haematological presentations did not have leukaemia if they had not been diagnosed in their first visit.

CONCLUSIONS

We described a clinical picture in the year before leukaemia diagnosis. These findings revealed ongoing difficulties in early diagnosis of childhood leukaemia in healthcare settings.

Acute lymphoblastic leukemia in a 2-year-old girl whose mother was previously diagnosed with antiphospholipid syndrome: a case report

BACKGROUND

The role of maternal exposures and conditions in the origin of childhood cancer has been a subject of growing interest, but current evidence is inconclusive.

CASE PRESENTATION

We present a case detected in a multicenter case-control study evaluating the association between parental risk factors and childhood acute lymphoblastic leukemia (ALL). The patient is a Colombian girl who was diagnosed with ALL-L1 when she was 2 years old. Her mother had been diagnosed with antiphospholipid syndrome before pregnancy and had also been treated with subcutaneous injections of heparin. Other potentially relevant maternal and patient exposures are also reported in this paper.

CONCLUSION

We hypothesize that the maternal autoimmune disease could be a contributor in the causality network of the daughter's leukemia. However, the role of other exposures cannot be excluded.

Prenatal recruitment of participants for a birth cohort study including cord blood collection: results of a feasibility study in Bremen, Germany

BACKGROUND

Prospective birth cohort studies comprising follow up of children from pregnancy or birth over a long period of time, and collecting various biological samples at different times through the life-course offer a promising approach to enhance etiologic knowledge of various diseases. Especially for those where early lifetime exposures and conditions are thought to play an important role. The collection and storage of biological samples is a critical component in epidemiological studies, notably for research regarding prenatal exposures to various environmental factors as well as for DNA extraction. Our feasibility study for a birth cohort within the scope of etiology of childhood leukemia with prospective sampling of mothers and their future newborns aimed to investigate the willingness of pregnant women to participate in a birth cohort study involving collection of blood and umbilical cord blood samples. The overall aim was to develop practice-based research recommendations for a possible German birth cohort study.

METHODS

The study was conducted in Bremen, Germany, between January 2012 and March 2013. Pregnant women were eligible for recruitment if (i) their expected date of delivery was during the study recruitment phase (September 2012-February 2013), (ii) they planned to give birth at the cooperating hospital's obstetric unit and (iii) their knowledge of the German language was sufficient to understand study materials, details of participation and to fill out the prenatal self-administered questionnaire. Maternal blood and umbilical cord blood samples to be used for later research activities were collected and stored at a stem cell bank already collaborating with the hospital. 22 primary care gynecologists were invited to enroll pregnant women for the study and cooperation with one hospital was established. Expectant women were recruited during the last trimester of pregnancy, either during one of their prenatal care visits at their primary care gynecologist or later on in hospital by the attending obstetricians or project staff.

RESULTS

Of the 22 invited primary care gynecologists requested to enroll pregnant women for the study, 8 gynecologists actually collaborated. A total of 200 eligible women were invited to participate in the study, 48 (24%) of whom agreed. 34 women were enrolled by primary care gynecologists, with one gynecologist enrolling 26 women. Twelve of 14 women recruited via hospitals were enrolled by study staff. A total of 41 women consented to the collection of umbilical cord blood and maternal blood samples, and samples could be stored for 54% of them. Reason for non-participation were the uncertainty whether or not the full study would be conducted and the fact that the participants were not willing to decide for their children whether or not genetic information (cord blood) can be stored for research purposes.

CONCLUSION

Enrolling parents in a birth cohort study that includes biosampling is a challenge, but participation can be improved through close collaboration with primary care gynecologists and maternity hospitals. Cord blood collection may impede participation, especially when maternity hospitals offer an alternative option for cord blood donation.

Race/ethnicity and the risk of childhood leukaemia: a case-control study in California

BACKGROUND

We conducted a large registry-based study in California to investigate the association between race/ethnicity and childhood leukaemia focusing on two subtypes: acute lymphoblastic leukaemia (ALL) and acute myeloid leukaemia (AML).

METHODS

We obtained information on 5788 cases and 5788 controls by linking California cancer and birth registries. We evaluated relative risk of childhood leukaemia by race and ethnicity of the child and their parents using conditional logistic regression, with adjustment for potential confounders.

RESULTS

Compared with Whites, Black children had lower risk of ALL (OR=0.54, 95% CI 0.45 to 0.66) as well as children of Black/Asian parents (OR=0.31, 95% CI 0.10 to 0.94). Asian race was associated with increased risk of AML with OR=1.643, 95% CI 1.10 to 2.46 for Asian vs Whites; and OR=1.67, 95% CI 1.04 to 2.70 for Asian/Asian vs White/White. Hispanic ethnicity was associated with increased risk of ALL (OR=1.37, 95% CI 1.22 to 1.52). A gradient in risk of ALL was observed while comparing Hispanic children with both parents Hispanic, one parent Hispanic and non-Hispanic children (p Value for trend <0.0001). The highest risk of ALL was observed for children with a combination of Hispanic ethnicity and White race compared with non-Hispanic whites (OR=1.27, 95% CI 1.12 to 1.44). The lowest risk was observed for non-Hispanic blacks (OR=0.46, 95% CI 0.36 to 0.60). Associations for total childhood leukaemia were similar to ALL.

CONCLUSIONS

Our results confirm that there are ethnic and racial differences in the incidence of childhood leukaemia. These differences indicate that some genetic and/or environmental/cultural factors are involved in aetiology of childhood leukaemia.

Epigenetic landscape correlates with genetic subtype but does not predict outcome in childhood acute lymphoblastic leukemia

Although children with acute lymphoblastic leukemia (ALL) generally have a good outcome, some patients do relapse and survival following relapse is poor. Altered DNA methylation is highly prevalent in ALL and raises the possibility that DNA methylation-based biomarkers could predict patient outcome. In this study, genome-wide methylation analysis, using the Illumina Infinium HumanMethylation450 BeadChip platform, was carried out on 52 diagnostic patient samples from 4 genetic subtypes [ETV6-RUNX1, high hyperdiploidy (HeH), TCF3-PBX1 and dic(9;20)(p11-13;q11)] in a 1:1 case-control design with patients who went on to relapse (as cases) and patients achieving long-term remission (as controls). Pyrosequencing assays for selected loci were used to confirm the array-generated data. Non-negative matrix factorization consensus clustering readily clustered samples according to genetic subgroups and gene enrichment pathway analysis suggested that this is in part driven by epigenetic disruption of subtype specific signaling pathways. Multiple bioinformatics approaches (including bump hunting and individual locus analysis) were used to identify CpG sites or regions associated with outcome. However, no associations with relapse were identified. Our data revealed that ETV6-RUNX1 and dic(9;20) subtypes were mostly associated with hypermethylation; conversely, TCF3-PBX1 and HeH were associated with hypomethylation. We observed significant enrichment of the neuroactive ligand-receptor interaction pathway in TCF3-PBX1 as well as an enrichment of genes involved in immunity and infection pathways in ETV6-RUNX1 subtype. Taken together, our results suggest that altered DNA methylation may have differential impacts in distinct ALL genetic subtypes.

Updated investigations of cancer excesses in individuals born or resident in the vicinity of Sellafield and Dounreay

BACKGROUND

Earlier studies have shown raised risks of leukaemia and non-Hodgkin lymphoma in children, teenagers and young adults resident either at birth or diagnosis in Seascale. Some increases in cancer risk in these age groups have also been noted among those living around Dounreay. We aimed to update previous analyses relating to areas close to these nuclear installations by considering data from an additional 16 years of follow-up.

METHODS

Cross-sectional analyses compared cancer incidence rates for 1963-2006 among those aged 0-24 years at diagnosis living in geographically specified areas around either Sellafield or Dounreay with general population rates. Cancer incidence for the period 1971-2006 among the cohort of Cumbrian births between 1950 and 2006 was compared to national incidence for 1971-2006 using person-years analysis. Cancer among those born in the postcode sector closest to Dounreay was compared with that among those born in the three adjoining postcode sectors. Analyses considered both cancer overall and ICD-O-3 defined diagnostic subgroups including leukaemia, central nervous system tumours and other malignancies.

RESULTS

Apart from previously reported raised risks, no new significantly increased risks for cancer overall or any diagnostic subgroup were found among children or teenagers and young adults living around either nuclear installation. Individuals born close to the installations from 1950 to 2006 were not shown to be at any increased risk of cancer during the period 1971 to date.

CONCLUSIONS

Analysis of recent data suggests that children, teenagers and young adults currently living close to Sellafield and Dounreay are not at an increased risk of developing cancer. Equally, there is no evidence of any increased cancer risk later in life among those resident in these areas at birth.

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

Background

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

Methods

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

Results

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

Conclusions

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

Childhood leukaemia risks: from unexplained findings near nuclear installations to recommendations for future research

Recent findings related to childhood leukaemia incidence near nuclear installations have raised questions which can be answered neither by current knowledge on radiation risk nor by other established risk factors. In 2012, a workshop was organised on this topic with two objectives: (a) review of results and discussion of methodological limitations of studies near nuclear installations; (b) identification of directions for future research into the causes and pathogenesis of childhood leukaemia. The workshop gathered 42 participants from different disciplines, extending widely outside of the radiation protection field. Regarding the proximity of nuclear installations, the need for continuous surveillance of childhood leukaemia incidence was highlighted, including a better characterisation of the local population. The creation of collaborative working groups was recommended for consistency in methodologies and the possibility of combining data for future analyses. Regarding the causes of childhood leukaemia, major fields of research were discussed (environmental risk factors, genetics, infections, immunity, stem cells, experimental research). The need for multidisciplinary collaboration in developing research activities was underlined, including the prevalence of potential predisposition markers and investigating further the infectious aetiology hypothesis. Animal studies and genetic/epigenetic approaches appear of great interest. Routes for future research were pointed out.

Investigating the relationship between mortality from respiratory diseases and childhood acute lymphoblastic leukaemia in Hungary

Our aim was to investigate the ecological association between death from infectious disease of the respiratory system and the risk of acute lymphoid leukaemia (ALL) in children aged less than 7 years. Poisson regression analyses were carried out using overall data and gender-specific models. The study included 176 cases (92(52.3 %) boys and 84 (47.7 %) girls) of ALL in those aged 0-6 years in South Hungary. Eight cases were diagnosed before the age of 1 year. A significant risk of ALL disease was observed with higher levels of mortality from the chronic respiratory diseases (p = 0.035) and pneumonia (p = 0.010) among children aged 2-5 years (Odds Ratio for trend was 1.001 and 95%CI [1.000-1.002] and Odds ratio for trend was 1.013 and 95%CI [1.003-1.023], respectively). Significantly increased risk of childhood ALL was detected among children under 1 year of age residing in areas around birth with higher levels of mortality from influenza (Odds Ratio (OR) for trend was 1.05; 95%CI [1.01-1.09]; p = 0.012). This risk was also detected in girls (p < 0.001), but not in boys (p = 0.43). Our findings provide new evidence that will help to understand the different pattern of female and male childhood ALL occurrence , but further studies are needed using detailed individual medical history to clarify the role of influenza and other infectious diseases in the etiology of childhood ALL and to explain gender-specific effects.

Cross-space-time clustering of childhood cancer in Great Britain: evidence for a common aetiology

Previously, we identified space-time clustering in certain childhood cancers. This study aimed to determine whether there was cross-space-time clustering between different diagnostic groups. A total of 32,295 cases were diagnosed during 1969–1993. Cross-space-time clustering was analyzed by a second-order procedure based on Diggle's method. Locations were birth and diagnosis addresses. The following space-time combinations were examined: address and date of birth; address at birth and date of diagnosis; address and date of diagnosis. Cross-space-time clustering analyses considered clustering pairs of cases from two different diagnostic groups. Formal statistical significance was taken as p < 0.00067 and marginal significance 0.01 > p ≥ 0.00067. Based on address at birth and date of diagnosis, there was statistically significant cross-clustering between cases of HL and intracranial and intraspinal embryonal tumors (IIET), both aged 0–14 years (p < 0.0001). Based on address and date of birth, there was marginally significant cross-clustering between cases of lymphoid leukemia (LL) aged 5-14 years and Hodgkin lymphoma (HL) aged 0–14 years (p = 0.0019). Based on address and date of diagnosis there was marginally significant cross-clustering between cases of LL aged 1–4 years and soft tissue sarcoma (STS) aged 0–14 years (p = 0.0041). Findings from this study are consistent with possible common aetiological factors between different diagnostic groups. They suggest a common aetiology for the following pairs of diagnostic groups: HL and IIET; older cases of LL and HL; younger cases of LL and STS. The possibility of common infectious mechanisms should be explored.

Residential mobility of populations near UK power lines and implications for childhood leukaemia

Epidemiological studies suggest associations between childhood leukaemia and living near high-voltage power lines, but the most obvious potential causative agent, the magnetic fields produced by the power lines, is not supported by laboratory studies or a known mechanism. An alternative hypothesised explanation is if there is greater population mobility near power lines, linking to the findings of Kinlen that population mixing increases leukaemia rates. We used the names recorded in electoral registers to see whether people near power lines move house more often than the population as a whole. We did find variations, but only small ones, and not such as to support the hypothesis.

The pathophysiology of the hygiene hypothesis

There has been a considerable increase in the diagnosis of allergic diseases over the last decades. Prevalence of allergies in high-income countries and urban areas appears higher than in rural environments. While environmental factors like pollution or nutrition can be important, it is more likely that in the end they have a small association with allergies. Childhood infections and exposure to certain microbial antigens on the other hand seem to present a strong negative correlation with allergies, and therefore the increase of the allergic burden in the Western world has been frequently related to a decline of childhood infections giving birth to the "Hygiene Hypothesis". We address the issue with emphasis on the associated pathophysiology tightrope walking between the skepticism of the critics, which cast doubt on it, and the pilgrims' belief of having discovered allergy's Holy Grail.

Acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia occurs in both children and adults but its incidence peaks between 2 and 5 years of age. Causation is multifactorial and exogenous or endogenous exposures, genetic susceptibility, and chance have roles. Survival in paediatric acute lymphoblastic leukaemia has improved to roughly 90% in trials with risk stratification by biological features of leukaemic cells and response to treatment, treatment modification based on patients' pharmacodynamics and pharmacogenomics, and improved supportive care. However, innovative approaches are needed to further improve survival while reducing adverse effects. Prognosis remains poor in infants and adults. Genome-wide profiling of germline and leukaemic cell DNA has identified novel submicroscopic structural genetic changes and sequence mutations that contribute to leukaemogenesis, define new disease subtypes, affect responsiveness to treatment, and might provide novel prognostic markers and therapeutic targets for personalised medicine.