Aetiology of childhood leukaemia

Secular trend in disease burden of leukemia and its subtypes in China from 1990 to 2019 and its projection in 25 years

Leukemia and its subtypes impose a major public health challenge in China. Identifying the secular trend of leukemia burden is critical to facilitate optimal healthcare planning and improve the management of leukemia. The incidence rates of leukemia from 1990 to 2019 were collected from the Global Burden of Disease Study 2019 database according to the following: subtype (acute lymphocytic leukemia [ALL], acute myeloid leukemia [AML], chronic lymphocytic leukemia [CLL], chronic myelogenous leukemia [CML], and other leukemia subtypes), sex, and age group. The average annual percentage changes and relative risks were calculated using joinpoint regression and the age-period-cohort model, respectively. The Bayesian age-period-cohort model was also applied to predict the future trend of the incidence of leukemia and its subtypes in the next 25 years. From 1990 to 2019, the age-standardized incidence rates (ASIRs) of leukemia slightly declined in males and females, which is similar to the trend of other leukemia subtypes. However, the four major leukemia subtypes, namely, ALL, AML, CLL, and CML, have been on the rise over the past three decades. The incidence rates of leukemia in children and the elderly were considerably higher than those in other age groups in males and females. Age effects were the most influential risk factor for leukemia incidence. Period effects showed that the risks of leukemia and its subtypes incidence increased with time. For cohort effects, the risks of leukemia and its subtypes were higher among the early-born cohorts compared with the late-born cohorts. The ASIRs of leukemia and its subtypes will continue to increase in the next 25 years. The burden of leukemia and its subtypes is expected to continue to increase in the next 25 years in males and females. A comprehensive understanding of the risk characteristics and disease pattern of leukemia and its subtypes is needed to formulate timely and effective intervention measures to reduce the leukemia burden in China.

Linking Benzene, in Utero Carcinogenicity and Fetal Hematopoietic Stem Cell Niches: A Mechanistic Review

Previous research reported that prolonged benzene exposure during in utero fetal development causes greater fetal abnormalities than in adult-stage exposure. This phenomenon increases the risk for disease development at the fetal stage, particularly carcinogenesis, which is mainly associated with hematological malignancies. Benzene has been reported to potentially act via multiple modes of action that target the hematopoietic stem cell (HSCs) niche, a complex microenvironment in which HSCs and multilineage hematopoietic stem and progenitor cells (HSPCs) reside. Oxidative stress, chromosomal aberration and epigenetic modification are among the known mechanisms mediating benzene-induced genetic and epigenetic modification in fetal stem cells leading to in utero carcinogenesis. Hence, it is crucial to monitor exposure to carcinogenic benzene via environmental, occupational or lifestyle factors among pregnant women. Benzene is a well-known cause of adult leukemia. However, proof of benzene involvement with childhood leukemia remains scarce despite previously reported research linking incidences of hematological disorders and maternal benzene exposure. Furthermore, accumulating evidence has shown that maternal benzene exposure is able to alter the developmental and functional properties of HSPCs, leading to hematological disorders in fetus and children. Since HSPCs are parental blood cells that regulate hematopoiesis during the fetal and adult stages, benzene exposure that targets HSPCs may induce damage to the population and trigger the development of hematological diseases. Therefore, the mechanism of in utero carcinogenicity by benzene in targeting fetal HSPCs is the primary focus of this review.

Human development and reproduction in space-a European perspective

This review summarises key aspects of the first reproductive and developmental systems Science Community White Paper, supported by the European Space Agency (ESA). Current knowledge regarding human development and reproduction in space is mapped to the roadmap. It acknowledges that sex and gender have implications on all physiological systems, however, gender identity falls outside the scope of the document included in the white paper collection supported by ESA. The ESA SciSpacE white papers on human developmental and reproductive functions in space aim to reflect on the implications of space travel on the male and female reproductive systems, including the hypothalamic-pituitary-gonadal (HPG) reproductive hormone axis, and considerations for conception, gestation and birth. Finally, parallels are drawn as to how this may impact society as a whole on Earth.

Widening Social Inequalities in Cancer Mortality of Children Under 5 Years in Korea

BACKGROUND

To investigate the effect of parental social class on cancer mortality in children under 5 in Korea, two birth cohorts were constructed by linking national birth data to under-5 death data from the Statistics Korea for 1995-1999 (3,323,613 births) and 2010-2014 (2,297,876 births).

METHODS

The Cox proportional hazards model adjusted for covariates was used in this study.

RESULTS

Social inequalities of under-5 cancer mortality risk in paternal education and paternal employment status were greater in 2010-2014 than in 1995-1999. The gap of hazard ratio (HR) of under-5 cancer mortality between lower (high school or below) and higher (university or higher) paternal education increased from 1.23 (95% confidence interval, 1.041.46) in 1995-1999 to 1.45 (1.11-1.97) in 2010-2014; the gap of HR between parents engaged in manual work and non-manual work increased from 1.32 (1.12-1.56) in 1995-1999 to 1.45 (1.12-1.89) in 2010-2014 for fathers, and from 1.18 (0.7-1.98) to 1.69 (1.03-2.79) for mothers. When the parental social class was lower, the risk of under-5 cancer mortality was higher in not only adverse but normal births.

CONCLUSION

Social inequalities must be addressed to reduce the disparity in cancer mortality of children under 5 years old.

Unconventional Oil and Gas Development Exposure and Risk of Childhood Acute Lymphoblastic Leukemia: A Case-Control Study in Pennsylvania, 2009-2017

BACKGROUND

Unconventional oil and gas development (UOGD) releases chemicals that have been linked to cancer and childhood leukemia. Studies of UOGD exposure and childhood leukemia are extremely limited.

OBJECTIVE

The objective of this study was to evaluate potential associations between residential proximity to UOGD and risk of acute lymphoblastic leukemia (ALL), the most common form of childhood leukemia, in a large regional sample using UOGD-specific metrics, including a novel metric to represent the water pathway.

METHODS

We conducted a registry-based case-control study of 405 children ages 2-7 y diagnosed with ALL in Pennsylvania between 2009-2017, and 2,080 controls matched on birth year. We used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between residential proximity to UOGD (including a new water pathway-specific proximity metric) and ALL in two exposure windows: a primary window (3 months preconception to 1 y prior to diagnosis/reference date) and a perinatal window (preconception to birth).

RESULTS

Children with at least one UOG well within 2 km of their birth residence during the primary window had 1.98 times the odds of developing ALL in comparison with those with no UOG wells [95% confidence interval (CI): 1.06, 3.69]. Children with at least one vs. no UOG wells within 2 km during the perinatal window had 2.80 times the odds of developing ALL (95% CI: 1.11, 7.05). These relationships were slightly attenuated after adjusting for maternal race and socio-economic status [odds ratio (OR) = 1.74 (95% CI: 0.93, 3.27) and OR = 2.35 (95% CI: 0.93, 5.95)], respectively). The ORs produced by models using the water pathway-specific metric were similar in magnitude to the aggregate metric.

DISCUSSION

Our study including a novel UOGD metric found UOGD to be a risk factor for childhood ALL. This work adds to mounting evidence of UOGD's impacts on children's health, providing additional support for limiting UOGD near residences. https://doi.org/10.1289/EHP11092.

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

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

Trends in childhood cancer incidence in sub-Saharan Africa: Results from 25 years of cancer registration in Harare (Zimbabwe) and Kyadondo (Uganda)

We examined trends in childhood cancer incidence in sub-Saharan Africa using data from two population-based cancer registries in Harare (Zimbabwe) and Kyadondo (Uganda) with cases classified according to the International Classification of Childhood Cancer and explored reasons for observed variations and changes. Over the whole 25-year period (1991-2015) studied, there were only small, and nonsignificant overall trends in incidence. Nevertheless, within the period, peaks in incidence occurred from 1996 to 2001 in Harare (Zimbabwe) and from 2003 to 2006 in Kyadondo (Uganda). Kaposi sarcoma and non-Hodgkin lymphoma accounted for the majority of the cases during these periods. These fluctuations in incidence rates in both registries can be linked to similar trends in the prevalence of HIV, and the availability of antiretroviral therapy. In addition, we noted that, in Harare, incidence rates dropped from 2003 to 2004 and 2007 to 2008, correlating with declines in national gross domestic product. The results indicate that the registration of childhood cancer cases in resource-poor settings is linked to the availability of diagnostic services mediated by economic developments. The findings highlight the need for specialised diagnostic and treatment programmes for childhood cancer patients as well as positive effects of HIV programmes on certain childhood cancers.

Residential exposure to natural background radiation at birth and risk of childhood acute leukemia in France, 1990-2009

BACKGROUND

The role of natural background radiation (NBR) in childhood acute leukemia (AL) remains unclear. Several large record based studies have recently reported heterogeneous results. Differences in exposure assessment timing may explain this heterogeneity.

OBJECTIVES

In a previous ecological study we did not observe any association between childhood AL incidence in France and NBR exposure at the time of diagnosis. With the same methodology, the present study focused on NBR exposure at the time of birth. Based on data from the French national registry of childhood cancer, we analyzed all AL together, and lymphoblastic and myeloid AL, separately.

METHODS

We included 6,059 childhood AL cases born and diagnosed in mainland France between 1990 and 2009. NBR levels in municipalities of residence at birth were estimated by cokriging models, using NBR measurements and precise geological data. The incidence rate ratio (IRR) per unit variation of exposure was estimated with Poisson regression models, with adjustment for socio-demographic indicators and ultraviolet radiation levels. NBR exposures were considered at the time of birth, and cumulatively from birth to diagnosis. We also estimated a total NBR dose to red-bone marrow (RBM).

RESULTS

There was no evidence for an association between NBR exposure at birth and childhood AL incidence, neither overall (gamma radiation: IRR = 0.99 (0.94,1.05) per 50 nSv/h; radon: IRR = 0.97 (0.91,1.03) per 100 Bq/m³) nor for the main AL types. The conclusions were similar with the cumulative exposures, and the total RBM dose.

CONCLUSIONS

The study was based on high quality incidence data, large numbers of AL cases, and validated models of NBR exposure assessment. In all, the results further support the hypothesis that NBR are not associated to childhood AL in France.

Birth characteristics and childhood leukemia in Switzerland: a register-based case-control study

Purpose

Initial genetic alterations in the development of childhood leukemia occur in utero or before conception; both genetic and environmental factors are suspected to play a role. We aimed to investigate the associations between childhood leukemia and perinatal characteristics including birth order, birth interval to older siblings, parental age, birth weight, and multiple birth.

Methods

We identified cases diagnosed between 1981 and 2015 and born in Switzerland between 1969 and 2015 from the Swiss Childhood Cancer Registry and randomly sampled five controls per case from national birth records matched on date of birth, sex, and municipality of residence at birth. We used conditional logistic regression to investigate associations between perinatal characteristics and leukemia at ages 0–15 and 0–4 years, and the subtypes acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML).

Results

The study included 1,403 cases of leukemia. We observed increased risks associated with high birth weight (adjusted OR 1.37, 95% CI 1.12–1.69) and multiple birth (1.89, 1.24–2.86). These associations were similar for ALL and stronger for leukemia at ages 0–4 years. For AML, we observed an increased risk for higher birth order (3.08, 0.43–22.03 for fourth or later born children). We found no associations with other perinatal characteristics.

Conclusion

This register-based case–control study adds to the existing evidence of a positive association between high birth weight and risk of childhood leukemia. Furthermore, it suggests children from multiple births are at an increased risk of leukemia.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10552-021-01423-3.

Seasonal variations in childhood leukaemia incidence in France, 1990-2014

BACKGROUND

Several studies have addressed the potential seasonality of childhood acute leukaemia (AL) without conclusive results. Using data from the National Registry of Childhood Cancers over 1990-2014 in mainland France, we investigated the seasonal variations in childhood AL taken together, and lymphoblastic (ALL) and myeloid (AML) leukaemia separately.

METHODS

Assuming constant variations over 1990-2014, we used a Poisson regression model to evaluate variations in standardized incidence ratios (SIRs) by month of birth or diagnosis. A scan method for temporal cluster detection was used to identify windows of several consecutive months with high or low SIR. The yearly reproducibility of the observed monthly variations was then evaluated.

RESULTS

We included 11,528 AL, of which 9493 ALL and 1,843 AML. No seasonal variation was detected for ALL. With a clear seasonal pattern, differences in AML incidence rates were evidenced between January-April and May-December birth periods (SIR = 0.85, 95% CI 0.77-0.94 and SIR = 1.07, 95% CI 1.01-1.14, respectively). AML incidence variations by month of diagnosis were less clear-cut.

CONCLUSION

Based on a large number of cases from a high-quality registry, we did not evidence any seasonality in ALL incidence rates but evidenced seasonal variations in AML incidence rates by month of birth.

The CEBPE rs2239633 genetic polymorphism on susceptibility to childhood acute lymphoblastic leukemia: an updated meta-analysis

Objectives

We performed an updated meta-analysis to clarify the relationship between the CEBPE rs2239633 polymorphism and the childhood acute lymphoblastic leukemia (CALL) susceptibility.

Methods

All the case-control studies were updated on October 5, 2020, through Web of Science, PubMed, Cochrane Library, Embase, and China National Knowledge Infrastructure (CNKI) electronic database. The heterogeneity in the study was tested by the Q test and I², and then the random ratio or fixed effect was utilized to merge the odds ratios (OR) and 95% confidence interval (CI). We also performed sensitivity analysis to estimate the impact of individual studies on aggregate estimates. Publication bias was investigated by using funnel plot and Egger’s regression test. All statistical analyses were performed using Stata 12.0.

Results

A total of 20 case-control studies were selected, including 7014 patients and 16,428 controls. There was no association of CEBPE rs2239633 polymorphism with CALL (CC vs CT + TT: OR = 1.08, 95% CI = 0.94–1.26; CC + CT vs TT: OR = 1.10, 95% CI = 0.94–1.30; C vs T: OR = 1.02, 95% CI = 0.92–1.13). In the subgroup analysis by ethnicity, there is no significant association of this polymorphism and CALL risks among Asian and Caucasian populations in the three genetic models (CC vs CT + TT, CC + CT vs TT, and C vs T).

Conclusion

This meta-analysis found no significant association between the CEBPE rs2239633 polymorphism and susceptibility to CALL.

Monthly variation in diagnosis of acute lymphoblastic leukemia and survival outcome in children and adults: 15-year trends at a single center

BACKGROUND

The date of acute lymphoblastic leukemia (ALL) diagnosis has been studied regarding potential etiologic roles with contrasting results and the issue remains controversial. The principal aim of this study was to analyze monthly variation of ALL diagnosis in a large homogenous Hispanic Latin American cohort over 15 years; its association with survival rates was also assessed.

METHODS

Clinical files and electronic records of 501 consecutive patients of all ages with ALL in northeastern Mexico over the years of 2004-2018 were scrutinized. Patients were divided into children ≤18 and adults >18 years. The Chi-square heterogeneity analysis was used to test for non-uniform variation. The Poisson regression analysis was used to fit sinusoidal (harmonic) models to the data, using the month of diagnosis as a covariate in a separate model.

RESULTS

During the study period 363 children (72.5%) and 138 adults (27.5%) (p < 0.001) were diagnosed with ALL. Heterogeneity across the months of diagnosis was confirmed (p = 0.019) and the Poisson regression analysis confirmed a significant monthly variation (p < 0.001) (95% CI, 3.024-3.745), a higher annual peak being observed in the month of March (p = 0.002), followed by a second peak in October (p = 0.026). The five-year OS for children was 68.2% (95% CI, 67.64-68.74) and for adults, 43.7% (95% CI, 42.67-44.71) (p < 0.001). No significant association between the month of diagnosis and OS was found (p = 0.789).

CONCLUSION

The monthly variation of ALL diagnosis was documented; these results confirm the heterogeneous behavior of the disease and appear to be consistent with an interplay of environmental and biologic factors. Further studies are needed to examine putative candidate agents.

Association between leukemia incidence and mortality and residential petrochemical exposure: A systematic review and meta-analysis

BACKGROUND

The global burden of leukemia, which grew by 19% from 2007 to 2017, poses a threat to human development and global cancer control. Factors contributing to this growth include massive industrial pollution, especially from large-scale petrochemical industry complexes (PICs). Globally, around 700 PICs are continuously operating. Data on the impact of PICs on leukemia incidence and mortality in residents are sparse and inconsistent.

OBJECTIVE

To determine the association between residential exposure to PICs and leukemia incidence and mortality using systematic review and meta-analysis.

METHODS

The studies were identified through seven databases (Clinical Key, Cochrane Library, EBSCOhost, Embase, PubMed, ScienceDirect, and Web of Science). We screened the eligibility of studies using following criteria: (1) observational studies that focused on residential exposure to PICs; (2) exposure group that was defined as residents living close to PICs; (3) outcome that was defined as all leukemia incidence and mortality; and (4) available population data. We applied the Grading of Recommendations Assessment, Development, and Evaluation to assess the certainty of evidence. The random-effects model used to estimate the pooled effects in the meta-analysis.

RESULTS

We identified thirteen epidemiologic studies (including eleven for leukemia incidence, one for leukemia mortality, and one for both), covering 125,580 individuals from Croatia, Finland, Italy, Serbia, Spain, Sweden, Taiwan, the United Kingdom, and the United States. We found moderate certainty of evidence indicated the risk of leukemia incidence (relative risk [RR] = 1.18; 95% CI = 1.03-1.35) and mortality (RR = 1.26; 95% CI = 1.10-1.45) in residents living close to PICs. Our subgroup analysis found increased RRs for leukemia incidence in studies using distance-based exposure indicator (RR = 1.11; 95% CI = 1.00-1.23), and with longer follow-up periods (RR = 1.24; 95% CI = 1.06-1.45).

CONCLUSION

Our analysis provides low-certainty evidence of increased leukemia incidence and moderate-certainty evidence of increased leukemia mortality among residents living close to PICs. While the global petrochemicals sector is growing, our findings suggest the need to consider disease prevention and pollution control measures during the development of PICs.

Erythroleukemia treated effects of rat plasma profile and erythrocyte membranes

Erythroleukemia disease is caused by over production of malignant blood and immature large number of blood cells enters into peripheral compartment. Biophysical and biochemical changes in plasma and erythrocyte membrane in erythroleukemia treated rats were identified. Our study, leukemia is experimentally exposed in rats were injecting erythroleukemia cells (FLC) (H-2d) intravenously in adult rats and normal control rats were maintained. Significant increase in the activity of blood glucose, proteins levels, aspartate transaminase (AST) and alanine transaminase (ALT) values and significant decrease in haemoglobin (Hb), albumin levels in erythroleukemia treated rats were observed when compared with control rats. Cholesterol and low density liproprotein (LDL) levels increased significantly in erythroleukemia treated rats but triglycerides, high density lipoprotein (HDL) and very low density lipoprotein (VLDL) levels decreased significantly. Levels of red cell membrane cholesterol decreased in erythroleukemia treated rats in comparison with control while levels of phospholipids and proteins increased in erythrocytes of erythroleukemia treated rats. Red blood cell (RBC) and white blood cell (WBC) counts increased significantly and platelet count decreased. C/P (cholesterol/phospholipid) ratio decreased significantly in erythroleukemia treated rats. This study has been undertaken for the first time to investigate the effect of (FLC) (H-2d) erythroleukemia cells (treated) in intravenously in adult rats and normal control rats. Results indicate biophysical and biochemical alterations at molecular level in plasma and erythrocyte membrane.

Is There A Causal Relationship between Childhood Obesity and Acute Lymphoblastic Leukemia? A Review

Simple Summary

The childhood obesity epidemic is impacting tens of millions of children globally. While obesity causes several cancers in adults, its potential role in causing pediatric cancers remains unclear. In this review, we assess the potential contribution of obesity to the development of acute lymphoblastic leukemia (ALL), the most common pediatric cancer. We review the possible mechanisms by which the adipose tissue attracts and protects leukemia cells and how it interferes with the actions of chemotherapies used in ALL treatment. We also examine adipose tissue-secreted molecules and fuels that may support leukemia development. While there are no current definite causal links between obesity and ALL, there are plausible mechanisms that need further investigation to explore the impact of obesity on causing ALL and on impacting treatment outcomes.

Abstract

Childhood obesity is a growing epidemic with numerous global health implications. Over the past few years, novel insights have emerged about the contribution of adult obesity to cancer risk, but the evidence base is far more limited in children. While pediatric patients with acute lymphoblastic leukemia (ALL) are at risk of obesity, it is unclear if there are potential causal mechanisms by which obesity leads to ALL development. This review explores the endocrine, metabolic and immune dysregulation triggered by obesity and its potential role in pediatric ALL’s genesis. We describe possible mechanisms, including adipose tissue attraction and protection of lymphoblasts, and their impact on ALL chemotherapies’ pharmacokinetics. We also explore the potential contribution of cytokines, growth factors, natural killer cells and adipose stem cells to ALL initiation and propagation. While there are no current definite causal links between obesity and ALL, critical questions persist as to whether the adipose tissue microenvironment and endocrine actions can play a causal role in childhood ALL, and there is a need for more research to address these questions.

Childhood central nervous system tumors and leukemia: Incidence and familial risk. A comparative population-based study in Utah and Norway

BACKGROUND

In this study, we aimed to evaluate incidence rates and family risk of the most common childhood cancers, tumors in the central nervous system (CNS), and leukemia among individuals from Norway and individuals with Scandinavian ancestry living in Utah.

METHODS

We used the Utah Population Database and the Norwegian National Population Register linked to Cancer registries to identify cancers in children born between 1966 and 2015 and their first-degree relatives. We calculated incidence rates and hazards ratios.

RESULTS

The overall incidence of CNS tumors increased with consecutive birth cohorts similarly in Utah and Norway (both P < 0.001). Incidence rates of leukemia were more stable and similar in both Utah and in Norway with 4.6/100 000 person-years among children (<15 years) born in the last cohort. A family history of CNS tumors was significantly associated with risk of childhood CNS tumors in Utah HR = 3.05 (95% CI 1.80-5.16) and Norway HR = 2.87 (95% CI 2.20-3.74). In Norway, children with a first-degree relative diagnosed with leukemia had high risk of leukemia (HR = 2.39, 95% CI 1.61-3.55).

CONCLUSION

Despite geographical distance and assumed large lifestyle differences, two genetically linked pediatric populations show similar incidences of CNS tumors and leukemia in the period 1966-2015. CNS tumors and leukemia aggregated in families in both countries.

Maternal Infection in Pregnancy and Childhood Leukemia: A Systematic Review and Meta-analysis

OBJECTIVE

To summarize the published evidence regarding the association between maternal infection during pregnancy and childhood leukemia.

STUDY DESIGN

In this systematic review and meta-analysis (PROSPERO number, CRD42018087289), we searched PubMed and Embase to identify relevant studies. We included human studies that reported associations of at least one measure of maternal infection during pregnancy with acute lymphoblastic leukemia (ALL) or all childhood leukemias in the offspring. One reviewer extracted the data first using a standardized form, and the second reviewer independently checked the data for accuracy. Two reviewers used the Newcastle-Ottawa Scale to assess the quality of included studies. We conducted random effects meta-analyses to pool the ORs of specific type of infection on ALL and childhood leukemia.

RESULTS

This review included 20 studies (ALL, n = 15; childhood leukemia, n = 14) reported in 32 articles. Most (>65%) included studies reported a positive association between infection variables and ALL or childhood leukemia. Among specific types of infection, we found that influenza during pregnancy was associated with higher risk of ALL (pooled OR, 3.64; 95% CI, 1.34-9.90) and childhood leukemia (pooled OR, 1.77; 95% CI, 1.01-3.11). Varicella (pooled OR, 10.19; 95% CI, 1.98-52.39) and rubella (pooled OR, 2.79; 95% CI, 1.16-6.71) infections were also associated with higher childhood leukemia risk.

CONCLUSIONS

Our findings suggest that maternal infection during pregnancy may be associated with a higher risk of childhood leukemia.

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.

Paternal Smoking Before Conception and During Pregnancy Is Associated With an Increased Risk of Childhood Acute Lymphoblastic Leukemia: A Systematic Review and Meta-Analysis of 17 Case-Control Studies

OBJECTIVE

Current evidence regarding the association between paternal smoking before conception or during pregnancy and the risk of childhood acute lymphoblastic leukemia (ALL) are inconsistent. We aimed to systematically summarize the current evidence regarding this potential association.

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and the Meta-analysis of Observational Studies in Epidemiology (MOOSE), we systematically retrieved PubMed, Embase, Web of Science, and Scopus, screened relevant literature, and assessed the methodologic quality of the included studies. We calculated the pooled estimates using random-effects models. We assessed statistical heterogeneity by I values and χ tests for the Cochrane Q statistic. We further investigate the dose-response relation using 2-stage nonlinear models.

RESULTS

A total of 17 case-control studies were identified, and the synthesized risk ratios (RRs) for smoking before conception (RR=1.15, 95% confidence interval: 1.04-1.27) and during pregnancy (RR=1.20, 95% confidence interval: 1.12-1.28) were both statistically significant. Moreover, the dose-response analysis showed a positive association as well.

CONCLUSION

Current evidence from observational studies suggests the association between paternal smoking before conception or during pregnancy and the increased risk of childhood ALL, which needs to be confirmed in prospective studies.

The Epidemiological Trend of Acute Myeloid Leukemia in Childhood: a Population-Based Analysis

Acute myeloid leukemia (AML) is the fifth most common malignancy in children, and the prognosis for AML in children remains relatively poor. However, its incidence and survival trends based on a large sample size have not been reported.

Children diagnosed with AML between 1975 and 2014 were accessed from the Surveillance, Epidemiology, and End Results database. Incidence and survival trends were evaluated by age-adjusted incidence and relative survival rates (RSRs) and Kaplan-Meier analyses. Cox regression was performed to identify independent risk factors for child AML death.

The overall incidence of AML in childhood increased each decade between 1975 and 2014, with the total age-adjusted incidence increasing from 5.766 to 6.615 to 7.478 to 7.607 per 1,000,000 persons. In addition, the relative survival rates of AML in childhood improved significantly, with 5-year RSRs increasing from 22.40% to 39.60% to 55.50% to 68.30% over the past four decades (p < 0.0001). Furthermore, survival disparities among different races and socioeconomic statuses have continued to widen over the past four decades. Multivariate Cox regression analyses showed a higher risk of death in Black patients (HR = 1.245, 95% CI: 1.077-1.438, p = 0.003) with Whites as a reference.

These results may help predict future trends for AML in childhood, better design clinical trials by eliminating disparities, and ultimately improve clinical management and outcome.

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 epidemiological trend of acute promyelocytic leukemia over past four decades: a population-based analysis

The treatment regimens for acute promyelocytic leukemia (APL) dramatically changed over time. However, its survival trend, based on a large sample size has not been reported. Patients diagnosed with APL were accessed from the Surveillance, Epidemiology, and End Results database. Their incidence and survival trend were evaluated in overall and subgroup levels. The overall incidence of APL increased with an annual percentage change of 5.5% from 1992 to 2006 and remained stable thereafter. In addition, the 5-year relative survival rates of APL improved significantly, from 12.3 to 32.2% to 59.5 to 72.1% over past four decades (p < .0001), sharing similar trend with different subgroups. Importantly, survival disparities exist among races and different socioeconomic status groups, with superior survival in whites and patients in low-poverty regions. Increasing incidence urges for increased awareness of clinicians over diagnosis of APL. In addition, a wider insurance coverage may help balance survival gap.

Community Noise and Air Pollution Exposure During the Development of a Multi-Well Oil and Gas Pad

Unconventional oil and gas development (UOGD) in the United States is increasingly being conducted on multiwell pads (MWPs) and in residential areas. We measured air pollution, noise, and truck traffic during four distinct phases of UOGD: drilling, hydraulic fracturing, flowback, and production. We monitored particulate matter (PM_2.5), black carbon (BC), A-weighted (dBA), and C-weighted (dBC) noise using real-time instruments on 1 and 5 min time scales, and truck traffic for 4-7 days per phase at a large 22-well pad sited in a residential area of Weld County, Colorado. Hydraulic fracturing, which requires frequent truck trips to move supplies and diesel engines to power the process, had the highest median air pollution levels of PM_2.5 and BC and experienced the greatest number of heavy trucks per hour compared to other phases. Median air pollution was lowest during drilling at this MWP, possibly because an electric drill rig was used. The equivalent continuous noise level ( L_eq) exceeded guidelines of 50 dBA and 65 dBC for A-weighted and C-weighted noise, respectively, during all development phases. Our data show that these multiple stressors are present around the clock at these sites, and this work provides baseline measurements on likely human exposure levels near similarly sized MWPs.

Predictors of residential mobility and its impact on air pollution exposure among children diagnosed with early childhood leukemia

Epidemiology studies relying on one address to assign exposures over time share common methodological limitations in failing to account for mobility that may introduce potential exposure misclassification. Using Texas birth certificate and cancer registry data, we identified predictors of residential mobility among mothers of children diagnosed with early childhood leukemia in Texas from 1995 to 2011. We used U.S. Environmental Protection Agency (EPA) National Air Toxics Assessment data to estimate residential levels of benzene and 1,3-butadiene based on addresses at birth and diagnosis and applied mixed-effects ordinal logistic regression models to evaluate differences in exposure classification between the two time periods. In total, 55% of children moved from time of birth to diagnosis, although they generally did not move far (median distance moved was 8 km). Predictors of mobility, at delivery, included younger age, being unmarried and living in neighborhoods with high benzene levels, and, at diagnosis, increasing child's age and living in neighborhoods with low poverty rates. We observed that the odds of being assigned to a higher exposure quartile at diagnosis relative to the time of birth decreased by 31% for 1,3-butadiene (OR = 0.69, 95% CI 0.59-0.82) and by 12% for benzene (OR = 0.88, 95% CI 0.75, 1.05).

A Meta-analysis of Traffic-related Air Pollution and Risk of Childhood Leukemia

BACKGROUND

Many studies have analyzed the association between traffic-related air pollution and risk of childhood leukemia, but the results are inconsistent. Therefore, we performed this meta-analysis to investigate the association between traffic-related air pollution and risk of childhood leukemia.

METHODS

PubMed, Cochrane, and Embase databases were searched by the index words to identify eligible case-control studies, and relevant literature sources were also searched. The latest research was performed in September 2017. Odds ratio (OR) along with 95% confidence interval (95% CI) were used to analyzed the main outcomes.

RESULTS

Twenty-one case-control studies were included in the meta-analysis. The results indicated that in the studies of overall traffic density (OR: 1.01, 95% CI: 0.98-1.04), high traffic density (OR: 1.04, 95% CI: 0.91-1.17), moderate exposure to NO2 (OR: 1.02, 95% CI: 0.93-1.10), and benzene (OR: 1.04, 95% CI: 0.71-1.37), the risks of childhood leukemia incidence were higher in the case group than the control group, but no significant difference was found. In other analysis, no significant difference was observed in the risk of childhood leukemia in the 2 groups.

CONCLUSIONS

Current evidence suggests that childhood leukemia is associated with traffic density, and moderate exposure to NO2 and benzene. However, more high-quality studies are required to confirm the conclusions.

DNA damage signalling from the placenta to foetal blood as a potential mechanism for childhood leukaemia initiation

For many diseases with a foetal origin, the cause for the disease initiation remains unknown. Common childhood acute leukaemia is thought to be caused by two hits, the first in utero and the second in childhood in response to infection. The mechanism for the initial DNA damaging event are unknown. Here we have used in vitro, ex vivo and in vivo models to show that a placental barrier will respond to agents that are suspected of initiating childhood leukaemia by releasing factors that cause DNA damage in cord blood and bone marrow cells, including stem cells. We show that DNA damage caused by in utero exposure can reappear postnatally after an immune challenge. Furthermore, both foetal and postnatal DNA damage are prevented by prenatal exposure of the placenta to a mitochondrially-targeted antioxidant. We conclude that the placenta might contribute to the first hit towards leukaemia initiation by bystander-like signalling to foetal haematopoietic cells.

Childhood cancer incidence in Canada: demographic and geographic variation of temporal trends (1992-2010)

INTRODUCTION

Surveillance of childhood cancer incidence trends can inform etiologic research, policy and programs. This study presents the first population-based report on demographic and geographic variations in incidence trends of detailed pediatric diagnostic groups in Canada.

METHODS

The Canadian Cancer Registry data were used to calculate annual age-standardized incidence rates (ASIRs) from 1992 to 2010 among children less than 15 years of age by sex, age and region for the 12 main diagnostic groups and selected subgroups of the International Classification of Childhood Cancer (ICCC), 3rd edition. Temporal trends were examined by annual percent changes (APCs) using Joinpoint regression.

RESULTS

The ASIRs of childhood cancer among males increased by 0.5% (95% confidence interval (CI) = 0.2-0.9) annually from 1992 to 2010, whereas incidence among females increased by 3.2% (CI = 0.4-6.2) annually since 2004 after an initial stabilization. The largest overall increase was observed in children aged 1-4 years (APC = 0.9%, CI = 0.4-1.3). By region, the overall rates increased the most in Ontario from 2006 to 2010 (APC = 5.9%, CI = 1.9-10.1), and increased non-significantly in the other regions from 1992 to 2010. Average annual ASIRs for all cancers combined from 2006 to 2010 were lower in the Prairies (149.4 per million) and higher in Ontario (170.1 per million). The ASIRs increased for leukemias, melanoma, carcinoma, thyroid cancer, ependymomas and hepatoblastoma for all ages, and neuroblastoma in 1-4 year olds. Astrocytoma decreased in 10-14 year olds (APC = -2.1%, CI = -3.7 to -0.5), and among males (APC = -2.4%, CI = -4.6 to -0.2) and females (APC = -3.7%, CI = -5.8 to -1.6) in Ontario over the study period.

CONCLUSION

Increasing incidence trends for all cancers and selected malignancies are consistent with those reported in other developed countries, and may reflect the changes in demographics and etiological exposures, and artefacts of changes in cancer coding, diagnosis and reporting. Significant decreasing trend for astrocytoma in late childhood was observed for the first time.

Radiation exposure from computerized tomography and risk of childhood leukemia: Finnish register-based case-control study of childhood leukemia (FRECCLE)

The only well-established risk factors for childhood leukemia are high-dose ionizing radiation and Down syndrome. Computerized tomography is a common source of low-dose radiation. In this study, we examined the magnitude of the risk of childhood leukemia after pediatric computed tomography examinations. We evaluated the association of computed tomography scans with risk of childhood leukemia in a nationwide register-based case-control study. Cases (n=1,093) were identified from the population-based Finnish Cancer Registry and three controls, matched by gender and age, were randomly selected for each case from the Population Registry. Information was also obtained on birth weight, maternal smoking, parental socioeconomic status and background gamma radiation. Data on computed tomography scans were collected from the ten largest hospitals in Finland, covering approximately 87% of all pediatric computed tomography scans. Red bone marrow doses were estimated with NCICT dose calculation software. The data were analyzed using exact conditional logistic regression analysis. A total of 15 cases (1.4%) and ten controls (0.3%) had undergone one or more computed tomography scans, excluding a 2-year latency period. For one or more computed tomography scans, we observed an odds ratio of 2.82 (95% confidence interval: 1.05 – 7.56). Cumulative red bone marrow dose from computed tomography scans showed an excess odds ratio of 0.13 (95% confidence interval: 0.02 – 0.26) per mGy. Our results are consistent with the notion that even low doses of ionizing radiation observably increase the risk of childhood leukemia. However, the observed risk estimates are somewhat higher than those in earlier studies, probably due to random error, although unknown predisposing factors cannot be ruled out.

A greater birthweight increases the risk of acute leukemias in Mexican children-experience from the Mexican Interinstitutional Group for the Identification of the Causes of Childhood Leukemia (MIGICCL)

In Mexico, due to the high rates of diabetes, overweight, and obesity, there has also been noted an increased newborn weight, which may be contributing to the elevated incidence rate of childhood acute leukemia (AL). We conducted a case-control study in public hospitals of Mexico City aimed to know whether a greater weight at birth is associated with a higher risk of developing leukemia. We included incident cases with acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) diagnosed between 2010 and 2015. Controls were frequency-matched to the cases by age, sex, and health institution. Logistic regression analysis was performed adjusting risks by child's sex, overcrowding index, birth order, and mother's age at the time of pregnancy. Adjusted odds ratios (aORs) and 95% confidence intervals were calculated. A total of 1455 cases and 1455 controls were included. An evident association between ALL and child's birthweight ≥2500 g was found (aOR 2.06; 95% CI: 1.59, 2.66) and also, in those with birthweight ≥3500 g (aOR 1.19; 95% CI: 1.00, 1.41). In AML patients with birthweight ≥2500 g and ≥3500 g, an aOR of 1.77 (95% CI: 1.07, 2.94) and 1.42 (95% CI: 1.03-1.95) was observed, respectively. No association was noticed with either type of AL and a birthweight ≥4000 g. To sum up, we found a moderate association between not having a low birthweight and an increased risk of acute leukemias. Birthweight ≥3500 g was also a risk factor for both types of leukemia. This suggests that a greater birthweight may increase the risk of acute leukemias in Mexican children.

Epidemiological patterns of leukaemia in 184 countries: a population-based study

BACKGROUND

Leukaemia is a heterogeneous group of haemopoietic cancers that comprises a number of diverse and biologically distinct subgroups. We examine the leukaemia burden worldwide and highlight the distinct incidence patterns in order to elucidate explanatory factors that may support preventive measures and health resource planning. We aimed to estimate the global burden of leukaemia incidence according to the four major subtypes stratified by age and sex.

METHODS

In this population-based study, we assessed leukaemia incidence for the major subtypes using the Cancer Incidence in Five Continents Volume X (CI5-X), which includes data from 290 cancer registries in 68 countries covering the diagnostic period 2003-07, for all ages and both sexes. We then extracted counts and incidence rates in 184 countries for the year 2012 from IARC's GLOBOCAN database of national estimates. We calculated age-specific incidence rates per 100 000 person-years and age-standardised rates (ASRs) using the world standard population by country, sex, age group, and where applicable, by major subtypes. We excluded from all analyses registries for which the total number of leukaemia cases was less than 100 or the proportion of microscopically verified (MV%) cases was less than 80% (2572 cases).

FINDINGS

717 863 cases between 2003-07 were included in this analysis. More than 350 000 new leukaemia cases were estimated in 2012. We observed substantial variation in incidence between and within world regions. The highest leukaemia incidence rates for both sexes were estimated in Australia and New Zealand (ASR per 100 000 11·3 in males and 7·2 in females), Northern America (10·5 in males and 7·2 in females), and western Europe (9·6 in males and 6·0 in females), and the lowest was in in western Africa (1·4 in males and 1·2 in females). Rates were generally higher in males than females with an overall male to female ratio of 1·4. In children, acute lymphoblastic leukaemia was the main subtype in all studied countries in both sexes, and characterised by a bimodal age-specific pattern. The subtype distribution was more diverse in adults, with a relatively higher proportion of chronic lymphocytic leukaemia in most European and North American countries, whereas rates of acute lymphoblastic leukaemia remained relatively high among adults in selected South American, Caribbean, Asian, and African populations.

INTERPRETATION

Geographical disparities in leukaemia might partly be explained by quality of, and access to, health systems linked to resource levels, although there is probably a role for aetiological factors, including gene-environment interactions. The observed bimodal pattern could be due to different risk factors affecting different ages, and might include a genetic component.

FUNDING

European Commission's FP-7 Marie Curie Actions-People-COFUND.

The functional polymorphisms of ARID5B and IKZF1 are associated with acute myeloid leukemia risk in a Han Chinese population

Since two genome-wide association studies identified the same susceptible region at ARID5B and IKZF1 for acute leukemia in Caucasians in the same time, several research groups have confirmed the similar results in different ethnicities and of different acute leukemia subtypes (ALL and AML). However, the causal variants of these two genes were not identified. In this study, we systematically screened 6 potentially functional SNPs in ARID5B and IKZF1 genes, and conducted a case-control study including 660 AML cases and 1034 cancer-free controls to investigate the associations between these SNPs and AML risk. We found that the variant alleles of rs4509706 and rs11761922 could significantly increase the risk of AML (rs4509706: OR=1.35, 95%CI=1.12-1.62 in additive model; rs11761922: OR=1.29, 95%CI=1.02-1.62 in recessive model). Luciferase reporter assay showed that both rs11761922-G and rs4509706-C significantly increased the luciferase levels as compared with rs11761922-C and rs4509706-T in K562 cells (P<0.05 for rs11761922 and P<0.001 for rs4509706). Our results indicated that rs4509706 and rs11761922 may play important roles in AML development in Chinese population.

Infectious Agents in Childhood Leukemia

Acute leukemia is the most common pediatric cancer, representing one-third of all cancers that occurs in under 15 year olds, with a varied incidence worldwide. Although a number of advances have increased the knowledge of leukemia pathophysiology, its etiology remains less well understood. The role of infectious agents, such as viruses, bacteria, or parasites, in the pathogenesis of leukemia has been discussed. To date, several cellular mechanisms involving infectious agents have been proposed to cause leukemia following infections. However, although leukemia can be triggered by contact with such agents, they can also be beneficial in developing immune stimulation and protection despite the risk of leukemic clones. In this review, we analyze the proposed hypotheses concerning how infectious agents may play a role in the origin and development of leukemia, as well as in a possible mechanism of protection following infections. We review reported clinical observations associated with vaccination or breastfeeding, that support hypotheses such as early life exposure and the resulting early immune stimulation that lead to protection.

Childhood brain tumours, early infections and immune stimulation: A pooled analysis of the ESCALE and ESTELLE case-control studies (SFCE, France)

BACKGROUND

Few studies have investigated whether early infections and factors potentially related to early immune stimulation might be involved in the aetiology of childhood brain tumours (CBT). In this study, we investigated the associations between CBT with early day-care attendance, history of early common infections, atopic conditions (asthma/wheezing, eczema, allergic rhinitis), early farm residence/visits and contact with animals.

METHODS

We pooled data from two nationwide French case-control studies, the ESCALE and ESTELLE studies. Children with a CBT diagnosed between 1 and 14 years of age were identified directly from the French National Registry of Childhood Cancers, while population controls were recruited from telephone subscribers. Odds-ratios (OR) and 95% confidence intervals (CI) were estimated using logistic regression adjusted for potential confounders.

RESULTS

The analyses included 469 cases and 2719 controls. We found no association between attending a day-care centre (OR: 0.9, 95%CI: 0.7-1.2) or having had repeated common infections (OR: 0.9, 95%CI: 0.7-1.2) in the first year of life and the risk of CBT. There was also no association with a history of asthma/wheezing (OR: 0.8, 95%CI: 0.56-1.1). Farm visits (OR: 0.6, 95%CI: 0.5-0.8) as well as contact with pets (OR: 0.8, 95%CI: 0.6-1.0) in the first year of life were inversely associated with CBT.

CONCLUSIONS

Our findings suggest a protective effect of early farm visits and contact with pets, but not with other markers of early immune stimulation. This might be related to immune stimulation but needs further investigation.

Spatiotemporal Industrial Activity Model for Estimating the Intensity of Oil and Gas Operations in Colorado

Oil and gas (O&G) production in the United States has increased in the last 15 years, and operations, which are trending toward large multiwell pads, release hazardous air pollutants. Health studies have relied on proximity to O&G wells as an exposure metric, typically using an inverse distance-weighting (IDW) approach. Because O&G emissions are dependent on multiple factors, a dynamic model is needed to describe the variability in air pollution emissions over space and time. We used information on Colorado O&G activities, production volumes, and air pollutant emission rates from two Colorado basins to create a spatiotemporal industrial activity model to develop an intensity-adjusted IDW well-count metric. The Spearman correlation coefficient between this metric and measured pollutant concentrations was 0.74. We applied our model to households in Greeley, Colorado, which is in the middle of the densely developed Denver-Julesburg basin. Our intensity-adjusted IDW increased the unadjusted IDW dynamic range by a factor of 19 and distinguishes high-intensity events, such as hydraulic fracturing and flowback, from lower-intensity events, such as production at single-well pads. As the frequency of multiwell pads increases, it will become increasingly important to characterize the range of intensities at O&G sites when conducting epidemiological studies.

Contributions of IKZF1, DDC, CDKN2A, CEBPE, and LMO1 Gene Polymorphisms to Acute Lymphoblastic Leukemia in a Yemeni Population

BACKGROUND

Genome-wide and candidate gene association studies have previously revealed links between a predisposition to acute lymphoblastic leukemia (ALL) and genetic polymorphisms in the following genes: IKZF1 (7p12.2; ID: 10320), DDC (7p12.2; ID: 1644), CDKN2A (9p21.3; ID: 1029), CEBPE (14q11.2; ID: 1053), and LMO1 (11p15; ID: 4004). In this study, we aimed to conduct an investigation into the possible association between polymorphisms in these genes and ALL within a sample of Yemeni children of Arab-Asian descent.

METHODS

Seven single-nucleotide polymorphisms (SNPs) in IKZF1, three SNPs in DDC, two SNPs in CDKN2A, two SNPs in CEBPE, and three SNPs in LMO1 were genotyped in 289 Yemeni children (136 cases and 153 controls), using the nanofluidic Dynamic Array (Fluidigm 192.24 Dynamic Array). Logistic regression analyses were used to estimate ALL risk, and the strength of association was expressed as odds ratios with 95% confidence intervals.

RESULTS

We found that the IKZF1 SNP rs10235796 C allele (p = 0.002), the IKZF1 rs6964969 A>G polymorphism (p = 0.048, GG vs. AA), the CDKN2A rs3731246 G>C polymorphism (p = 0.047, GC+CC vs. GG), and the CDKN2A SNP rs3731246 C allele (p = 0.007) were significantly associated with ALL in Yemenis of Arab-Asian descent. In addition, a borderline association was found between IKZF1 rs4132601 T>G variant and ALL risk. No associations were found between the IKZF1 SNPs (rs11978267; rs7789635), DDC SNPs (rs3779084; rs880028; rs7809758), CDKN2A SNP (rs3731217), the CEBPE SNPs (rs2239633; rs12434881) and LMO1 SNPs (rs442264; rs3794012; rs4237770) with ALL in Yemeni children.

CONCLUSION

The IKZF1 SNPs, rs10235796 and rs6964969, and the CDKN2A SNP rs3731246 (previously unreported) could serve as risk markers for ALL susceptibility in Yemeni children.

Road Traffic Pollution and Childhood Leukemia: A Nationwide Case-control Study in Italy

BACKGROUND

The association of childhood leukemia with traffic pollution was considered in a number of studies from 1989 onwards, with results not entirely consistent and little information regarding subtypes.

AIM OF THE STUDY

We used the data of the Italian SETIL case-control on childhood leukemia to explore the risk by leukemia subtypes associated to exposure to vehicular traffic.

METHODS

We included in the analyses 648 cases of childhood leukemia (565 Acute lymphoblastic-ALL and 80 Acute non lymphoblastic-AnLL) and 980 controls. Information on traffic exposure was collected from questionnaire interviews and from the geocoding of house addresses, for all periods of life of the children.

RESULTS

We observed an increase in risk for AnLL, and at a lower extent for ALL, with indicators of exposure to traffic pollutants. In particular, the risk was associated to the report of closeness of the house to traffic lights and to the passage of trucks (OR: 1.76; 95% CI 1.03-3.01 for ALL and 6.35; 95% CI 2.59-15.6 for AnLL). The association was shown also in the analyses limited to AML and in the stratified analyses and in respect to the house in different period of life.

CONCLUSIONS

Results from the SETIL study provide some support to the association of traffic related exposure and risk for AnLL, but at a lesser extent for ALL. Our conclusion highlights the need for leukemia type specific analyses in future studies. Results support the need of controlling exposure from traffic pollution, even if knowledge is not complete.

Incidence and survival of childhood cancer in the French islands of Reunion and Mayotte (2005-2011)

The aim of this study is to describe childhood cancer incidence and survival in the French islands of Reunion and Mayotte for the period 2005-2011. Data were taken from the population-based Cancer Registry of Reunion Island. All incident cases of malignant tumours and benign tumours of the Central Nervous System diagnosed between 2005 and 2011 in children under the age of 15 and living in Reunion or Mayotte were included. A total of 236 cases were registered (176 in Reunion, 60 in Mayotte). Age-standardised incidence rates (ASRs, world standard) for all cancers were 125.0 and 101.8 per million for Reunion and Mayotte, respectively. ASRs for the main cancer groups were lower than those described in mainland France for the same period. The 5-year overall survival rate for all patients was 78.5% (95%CI 71.9- 83.7), slightly lower than that reported in mainland France.

Parental Exposure to Workplace Carcinogens and the Risk of Development of Acute Leukemia in Infants. Case-Control Study

BACKGROUND AND AIMS

Occupational exposure of parents to carcinogens is of great interest in the etiology of leukemias. Evidence of the impact of such exposure on infants or small children is scarce. Here we estimated whether occupational exposure of parents to carcinogens could be a risk factor for leukemias in their children.

METHODS

Cases of acute leukemia (AL) in infants ≤24 months old diagnosed in Mexico City (1998-2013) were included in a population-based, case-control study. Each of the 195 cases was matched with at least one healthy child (n = 369). For each of four exposure windows studied, the degree of exposure to carcinogens was determined for both parents by using a validated occupational exposure index. An unconditional logistic regression was carried out.

RESULTS

Odds ratios (OR) and the 95% confidence intervals (CI) of the overall occupational exposure for parents during the four exposure windows indicated no association with risk of AL in their children. Pre-conception, the OR by the father 0.77 (0.49-1.21), by the mother 1.03 (0.50-2.11); during pregnancy, father 0.66 (0.38-1.15), mother 1.79 (0.46-6.90); during breastfeeding, father 0.75 (0.43-1.30), mother 0.96 (0.21-4.30); and after birth, father 0.74 (0.45-1.22), mother 0.90 (0.24-3.32). The statistical power of the sample size to identify an OR ≥2 and an exposure of ≥10% among controls was 78%.

CONCLUSIONS

These data support the idea that parents' occupational exposure during any of the periods studied was not a risk factor contributing to the etiology of AL in infants ≤24 months of age.

Childhood hematologic cancer and residential proximity to oil and gas development

Background

Oil and gas development emits known hematological carcinogens, such as benzene, and increasingly occurs in residential areas. We explored whether residential proximity to oil and gas development was associated with risk for hematologic cancers using a registry-based case-control study design.

Methods

Participants were 0–24 years old, living in rural Colorado, and diagnosed with cancer between 2001–2013. For each child in our study, we calculated inverse distance weighted (IDW) oil and gas well counts within a 16.1-kilometer radius of residence at cancer diagnosis for each year in a 10 year latency period to estimate density of oil and gas development. Logistic regression, adjusted for age, race, gender, income, and elevation was used to estimate associations across IDW well count tertiles for 87 acute lymphocytic leukemia (ALL) cases and 50 non-Hodgkin lymphoma (NHL) cases, compared to 528 controls with non-hematologic cancers.

Findings

Overall, ALL cases 0–24 years old were more likely to live in the highest IDW well count tertiles compared to controls, but findings differed substantially by age. For ages 5–24, ALL cases were 4.3 times as likely to live in the highest tertile, compared to controls (95% CI: 1.1 to 16), with a monotonic increase in risk across tertiles (trend p-value = 0.035). Further adjustment for year of diagnosis increased the association. No association was found between ALL for children aged 0–4 years or NHL and IDW well counts. While our study benefited from the ability to select cases and controls from the same population, use of cancer-controls, the limited number of ALL and NHL cases, and aggregation of ages into five year ranges, may have biased our associations toward the null. In addition, absence of information on O&G well activities, meteorology, and topography likely reduced temporal and spatial specificity in IDW well counts.

Conclusion

Because oil and gas development has potential to expose a large population to known hematologic carcinogens, further study is clearly needed to substantiate both our positive and negative findings. Future studies should incorporate information on oil and gas development activities and production levels, as well as levels of specific pollutants of interest (e.g. benzene) near homes, schools, and day care centers; provide age-specific residential histories; compare cases to controls without cancer; and address other potential confounders, and environmental stressors.

Breastfeeding as a Protective Effect Against Childhood Leukemia and Lymphoma

Background

Over the past several years, breastfeeding has been associated with many benefits as well as protective effects against many diseases. There is limited evidence for the relationship between breastfeeding and the incidence of leukemia.

Objectives

In this study, we evaluate the correlation of childhood leukemia and lymphoma with breastfeeding duration in children in southern Iran.

Patients and methods

Through this case control study, we compared 123 patients with leukemia and lymphoma to a control group of 137 healthy children. Statistical analysis was done using the Chi-square test and t-test as well as logistic regression methods. A P-value of less than 0.05 was considered significant.

Results

Our findings showed that breastfeeding duration had no significant difference between cases and controls. However, the rural living percentage in patients with leukemia and lymphoma was higher than in the control group (39.8% versus 14.6% [P < 0.001 and OR = 3.87]) and parents’ exposure to chemical materials during the war between Iran and Iraq was higher in sick patients (6.5% versus 0% [OR = 20.2%]).

Conclusions

The current study showed that breastfeeding duration has no protective effect against childhood leukemia and lymphoma. In addition, we suggest that some factors such as living in a rural area, smoking during pregnancy, parents’ exposure to chemical materials and low socioeconomic status can increase the incidence rate of childhood leukemia and lymphoma.

Space-Time Clustering of Childhood Leukemia: Evidence of an Association with ETV6-RUNX1 (TEL-AML1) Fusion

BACKGROUND

Many studies have observed space-time clustering of childhood leukemia (CL) yet few have attempted to elicit etiological clues from such clustering. We recently reported space-time clustering of CL around birth, and now aim to generate etiological hypotheses by comparing clustered and nonclustered cases. We also investigated whether the clustering resulted from many small aggregations of cases or from a few larger clusters.

METHODS

We identified cases of persons born and diagnosed between 1985 and 2014 at age 0-15 years from the Swiss Childhood Cancer Registry. We determined spatial and temporal lags that maximized evidence of clustering based on the Knox test and classified cases born within these lags from another case as clustered. Using logistic regression adjusted for child population density, we determined whether clustering status was associated with age at diagnosis, immunophenotype, cytogenetic subtype, perinatal and socioeconomic characteristics, and pollution sources.

RESULTS

Analyses included 1,282 cases of which 242 were clustered (born within 1 km and 2 years from another case). Of all investigated characteristics only the t(12;21)(p13;q22) translocation (resulting in ETV6-RUNX1 fusion) differed significantly in prevalence between clustered and nonclustered cases (40% and 25%, respectively; adjusted OR 2.54 [1.52-4.23]; p = 0.003). Spatio-temporal clustering was driven by an excess of aggregations of two or three children rather than by a few large clusters.

CONCLUSION

Our findings suggest ETV6-RUNX1 is associated with space-time clustering of CL and are consistent with an infection interacting with that oncogene in early life leading to clinical leukemia.

Human development: from conception to maturity

Abstract The main objective of this review was to describe and emphasize the care that a woman must have in the period prior to pregnancy, as well as throughout pregnancy and after the birth of the baby, cares and duties that should continue to be followed by mother and child throughout the first years of the child’s life. Such cares are of nutritional, behavioral and lifestyle natures, and also involve the father and the whole family. Human development, from conception to maturity, consists of a critical and important period due to the multitude of intrinsic genetic and environmental factors that influence, positively or negatively, the person's entire life. The human being, who originated and passed his/her first phase of development in the womb, receives influence from different factors: a) of parental origin (father and mother), including health and lifestyle of the father and mother, genetic inheritance, nutrition of the mother prior to and during pregnancy; b) events that affected the mother and hence the child under development in intrauterine life, at birth (delivery), during perinatal period, and throughout the early years of life. The fragility of development continues throughout the preschool, school and adolescent periods during which proper nutrition with a balanced lifestyle is essential and depends on guidance from the parents, caregivers and teachers.

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.

Virome characterisation from Guthrie cards in children who later developed acute lymphoblastic leukaemia

Background:

Some childhood acute lymphoblastic leukaemias (ALL) can be traced back to a prenatal origin, where a virus infection could be involved in the first pre-leukaemic clone development. The DNA virome of 95 children who later developed ALL was characterised from neonatal blood spots (NBS) using unbiased next-generation sequencing (NGS) and compared with the virome of 95 non-ALL controls.

Methods:

DNA was individually extracted from the ALL-patients and controls, pooled, randomly amplified and sequenced using the Illumina MiSeq Sequencing System.

Results:

Virus-like sequences identified in both groups mapped to human endogenous retroviruses and propionibacterium phage, considered a part of the normal microbial flora. Potential pathogens human herpesvirus type 6 (HHV-6) and parvovirus B19 were also identified, but only few samples in both ALL and controls tested positive by PCR follow-up.

Conclusions:

Unbiased NGS was employed to search for DNA from potential infectious agents in neonatal samples of children who later developed ALL. Although several viral candidates were identified in the NBS samples, further investigation by PCR suggested that these viruses did not have a major role in ALL development.

Childhood leukemia incidence in California: High and rising in the Hispanic population

BACKGROUND

High rates of childhood leukemia incidence have been reported in Latin America and among Hispanic children in the United States. California's large Hispanic population affords an important opportunity to perform a detailed analysis of the leukemia burden among Hispanic children.

METHODS

Leukemias diagnosed among non-Hispanic white (NHW), Hispanic, African American (AA), and Asian/Pacific Islander (API) children aged birth to 19 years between January 1, 1990 and December 31, 2012 were obtained from the California Cancer Registry (11,084 cases). Age-adjusted incidence rates, standardized rate ratios (SRRs), and secular trends in incidence (annual percent change [APC]) were analyzed by subtype, race/ethnicity, sex, and age.

RESULTS

Compared with NHW children, the incidence of acute lymphoblastic leukemia (ALL) was higher among Hispanic (SRR, 1.32) and lower among AA (SRR, 0.55) and API (SRR, 0.91) children. From 1990 to 2012, the incidence of ALL increased overall (APC, 1.1%) and among males (APC, 1.0%), females (APC, 1.3%), Hispanics (APC, 1.1%), AAs (APC, 1.9%), AA males (APC, 2.8%), API males (APC, 1.9%), and Hispanic females (APC, 1.5%). The incidence of ALL increased among Hispanic males aged 15 to 19 years (APC, 2.5%) and Hispanic females aged birth to 4 years and 15 to 19 years (APCs of 2.2% and 1.9%, respectively). The incidence of acute myeloid leukemia did not appear to differ among racial/ethnic groups. From 1990 to 2012, the overall incidence of acute myeloid leukemia remained stable but increased among Hispanics (APC, 1.2%), females (APC, 1.0%), Hispanic females (APC, 2.3%), and Hispanic females aged 15 to 19 years (APC, 3.4%).

CONCLUSIONS

Notable differences in the incidence of childhood leukemia were observed among 4 racial/ethnic groups in California. Factors that may contribute to these differences include differential exposure to carcinogens and/or genetic susceptibility. Cancer 2016. © 2016 American Cancer Society. Cancer 2016;122:2867-2875. © 2016 American Cancer Society.