Overview of recent studies on childhood leukaemia, intra-uterine growth and diet

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

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

Socioeconomic Status and Childhood Leukemia Incidence in Switzerland

Socioeconomic status (SES) discrepancies exist for child and adult cancer morbidity and are a major public health concern. In this Swiss population-based matched case–control study on the etiology of childhood leukemia, we selected the cases from the Swiss Childhood Cancer Registry diagnosed since 1991 and the controls randomly from census. We assigned eight controls per case from the 1990 and 2000 census and matched them by the year of birth and gender. SES information for both cases and controls was obtained from census records by probabilistic record linkage. We investigated the association of SES with childhood leukemia in Switzerland, and explored whether it varied with different definitions of socioeconomic status (parental education, living condition, area-based SES), time period, and age. In conditional logistic regression analyses of 565 leukemia cases and 4433 controls, we found no consistent evidence for an association between SES and childhood leukemia. The odds ratio comparing the highest with the lowest SES category ranged from 0.95 (95% CI: 0.71–1.26; P_trend = 0.73) for paternal education to 1.37 (1.00–1.89; P_trend = 0.064) for maternal education. No effect modification was found for time period and age at diagnosis. Based on this population-based study, which avoided participation and reporting bias, we assume the potential association of socioeconomic status and childhood leukemia if existing to be small. This study did not find evidence that socioeconomic status, of Switzerland or comparable countries, is a relevant risk factor or strong confounder in etiological investigations on childhood leukemia.

The Childhood Leukemia International Consortium

BACKGROUND

Acute leukemia is the most common cancer in children under 15 years of age; 80% are acute lymphoblastic leukemia (ALL) and 17% are acute myeloid leukemia (AML). Childhood leukemia shows further diversity based on cytogenetic and molecular characteristics, which may relate to distinct etiologies. Case-control studies conducted worldwide, particularly of ALL, have collected a wealth of data on potential risk factors and in some studies, biospecimens. There is growing evidence for the role of infectious/immunologic factors, fetal growth, and several environmental factors in the etiology of childhood ALL. The risk of childhood leukemia, like other complex diseases, is likely to be influenced both by independent and interactive effects of genes and environmental exposures. While some studies have analyzed the role of genetic variants, few have been sufficiently powered to investigate gene-environment interactions.

OBJECTIVES

The Childhood Leukemia International Consortium (CLIC) was established in 2007 to promote investigations of rarer exposures, gene-environment interactions and subtype-specific associations through the pooling of data from independent studies.

METHODS

By September 2012, CLIC included 22 studies (recruitment period: 1962-present) from 12 countries, totaling approximately 31000 cases and 50000 controls. Of these, 19 case-control studies have collected detailed epidemiologic data, and DNA samples have been collected from children and child-parent trios in 15 and 13 of these studies, respectively. Two registry-based studies and one study comprising hospital records routinely obtained at birth and/or diagnosis have limited interview data or biospecimens.

CONCLUSIONS

CLIC provides a unique opportunity to fill gaps in knowledge about the role of environmental and genetic risk factors, critical windows of exposure, the effects of gene-environment interactions and associations among specific leukemia subtypes in different ethnic groups.

Hepatoblastoma in the Nordic countries

Little is known about the etiology of hepatoblastoma. Because of the young age at diagnosis, several studies have looked at various birth characteristics. The purpose of our study was to investigate the incidence of hepatoblastoma in the Nordic countries and the association between selected birth characteristics and hepatoblastoma. Data from national cancer registries and birth registries in Denmark, Sweden, Norway and Finland 1985-2006 was used. Overall, 155 children with hepatoblastoma aged 0-14 years were included and individually matched to five controls drawn randomly from national population registries. The incidence rate of hepatoblastoma was 1.7 per million person-years with a predominance of boys (1.5:1). Incidence rate was highest before the age of 1 year (8.3 per million person-years). A higher risk of hepatoblastoma was found in children with birth weight <1,500 g [odds ratio (OR) = 9.5; 95% confidence interval (CI): 2.3-38.2], born preterm in week 22-32 (OR = 4.5; CI: 1.8-11.5) and Apgar scores <7 after 1 min (OR = 3.1; CI: 1.3-7.1) and 5 min (OR = 7.5; CI: 1.8-32.4). A doubling in risk was found in children who were large for gestational age (OR = 2.3; CI: 1.0-5.3). No associations were found with birth order, maternal age or maternal smoking. Our study indicates that intrauterine and/or neonatal factors are associated with increased risk of hepatoblastoma. These may include low birth weight and asphyxia leading to neonatal intensive care. Alternatively, the factors may be a consequence of hepatoblastoma developing in utero.