Spatial clustering of childhood leukaemia with the integration of the Paediatric Environmental History

Trends in childhood leukemia incidence in urban countries and their relation to environmental factors, including space weather

Leukemia is the most common cancer in children. Its incidence has been increasing worldwide since 1910th, suggesting the presence of common sources of the disease, most likely related to people's lifestyle and environment. Understanding the relationship between childhood leukemia and environmental conditions is critical to preventing the disease. This discussion article examines established potentially-carcinogenic environmental factors, such as vehicle emissions and fires, alongside space weather-related parameters like cosmic rays and the geomagnetic field. To discern the primary contributor, we analyze trends and annual variations in leukemia incidence among 0-14-year-olds in the United States, Canada, Australia, and Russia from 1990 to 2018. Comparisons are drawn with the number of vehicles (representing gasoline emissions) and fire-affected land areas (indicative of fire-related pollutants), with novel data for Russia introduced for the first time. While childhood leukemia incidence is rising in all countries under study, the rate of increase in Russia is twice that of other nations, possibly due to a delayed surge in the country's vehicle fleet compared to others. This trend in Russia may offer insights into past leukemia levels in the USA, Canada, and Australia. Our findings highlight vehicular emissions as the most substantial environmental hazard for children among the factors examined. We also advocate for the consideration of potential modulation of carcinogenic effects arising from variations in cosmic ray intensity, as well as the protective role of the geomagnetic field. To support the idea, we provide examples of potential space weather effects at both local and global scales. The additional analysis includes statistical data from 49 countries and underscores the significance of the magnetic field dip in the South Atlantic Anomaly in contributing to a peak in childhood leukemia incidence in Peru, Ecuador and Chile. We emphasize the importance of collectively assessing all potentially carcinogenic factors for the successful future predictions of childhood leukemia risk in each country.

Looking Towards 2030: Strengthening the Environmental Health in Childhood-Adolescent Cancer Survivor Programs

Childhood and adolescent cancer survivors (CACS) are a high-risk population for non-communicable diseases and secondary carcinogenesis. The Environmental and Community Health Program for Longitudinal Follow-up of CACS in the region of Murcia, Spain, is an ongoing pioneering program that constitutes a model for social innovation. This study aims to present the program tools and protocol as a whole, as well as a profile of the incidence, survival, and spatiotemporal distribution of childhood cancer in the region of Murcia, Spain, using 822 sample cases of cancer diagnosed in children under 15 years of age (1998-2020). While the crude incidence rate across that entire period was 149.6 per 1 million, there was an increase over that time in the incidence. The areas with a higher standardized incidence ratio have shifted from the northwest (1998-2003) to the southeast (2016-2020) region. Overall, the ten-year survival rate for all tumor types was 80.1% over the entire period, increasing the five-year survival rate from 76.1 (1998-2003) to 85.5 (2014-2018). CACS living in areas with very poor outdoor air quality had lower survival rates. Furthermore, integrating environmental health into clinical practice could improve knowledge of the etiology and prognosis, as well as the outcomes of CACS. Finally, monitoring individual carbon footprints and creating healthier lifestyles, alongside healthier environments for CACS, could promote wellbeing, environmental awareness, and empowerment in order to attain Sustainable Development Goals for non-communicable diseases in this population.

The association between microRNA polymorphisms and the risk of childhood acute lymphoblastic leukemia: A meta-analysis

The aim of this meta-analysis was to determine the relationship between microRNA polymorphisms and the risk of childhood acute lymphoblastic leukemia comprehensively. PubMed, EMBASE, Scopus, Web of Science, the Cochrane Library, Global Index Medicus, Clinicaltrials.gov, ProQuest, and Open Grey databases were used to find relevant papers. Using the STATA 16.0 and CMA 3.0 software, the significance of relationships between microRNA polymorphisms and childhood acute lymphoblastic leukemia risk was evaluated using odds ratios (ORs) and 95 % confidence intervals (95 % CIs) for five genetic models. The results of the meta-analysis showed that there was no significant association between the polymorphism of miR-146a rs2910164 and childhood acute lymphoblastic leukemia risk in different genetic models. Also, in the sensitivity analysis, removing Xue's study from the analysis indicated that both the homozygote and recessive models are significantly affected. Additionally, there was a statistically significant relationship between the polymorphisms of pri-miR-34b/c rs4938723 (in the homozygote and recessive models) and miR-612 rs12803915 (in the allele and dominant models) and childhood acute lymphoblastic leukemia risk. These findings suggest that the rs4938723 and rs12803915 polymorphisms may have a role in the development of childhood acute lymphoblastic leukemia.

Ultrastructural changes in cristae of lymphoblasts in acute lymphoblastic leukemia parallel alterations in biogenesis markers

We explored the link between mitochondrial biogenesis and mitochondrial morphology using transmission electron microscopy (TEM) in lymphoblasts of pediatric acute lymphoblastic leukemia (ALL) patients and compared these characteristics between tumors and control samples. Gene expression of mitochondrial biogenesis markers was analysed in 23 ALL patients and 18 controls and TEM for morphology analysis was done in 15 ALL patients and 9 healthy controls. The area occupied by mitochondria per cell and the cristae cross-sectional area was observed to be significantly higher in patients than in controls (p-value = 0.0468 and p-value< 0.0001, respectively). The mtDNA copy numbers, TFAM, POLG, and c-myc gene expression were significantly higher in ALL patients than controls (all p-values< 0.01). Gene Expression of PGC-1α was higher in tumor samples. The analysis of the correlation between PGC-1α expression and morphology parameters i.e., both M/C ratio and cristae cross-sectional area revealed a positive trend (r = 0.3, p = 0.1). The increased area occupied by mitochondria and increased cristae area support the occurrence of cristae remodelling in ALL. These changes might reflect alterations in cristae dynamics to support the metabolic state of the cells by forming a more condensed network. Ultrastructural imaging can be useful for affirming changes occurring at a subcellular organellar level.

Spatial analysis and geoclimatic factors associated with the incidence of acute lymphoblastic leukemia in Iran during 2006-2014: An environmental epidemiological study

BACKGROUND AND OBJECTIVES

The present study aims to determine the cumulative incidence rate of acute lymphoblastic leukemia (ALL), the degree of spatial autocorrelation and clustering of ALL, the hotspot and coldspots of ALL and geoclimatic conditions affecting the incidence of ALL in Iran and to draw a comparison between global and local regression models.

MATERIALS AND METHODS

In this ecological study, an exploratory-etiologic multiple-group method has been adopted to investigate all children under 15 years of age with ALL in Iran during 2006-2014. Data analysis was performed using Mann Whitney U, Pearson correlation coefficients (PCCs), Global Moran's I, Optimized hotspot analysis (OHSA), Global Poisson regression (GPR), Geographically Weighted Poisson Regression (GWPR) at a significant level of α = 0.05.

RESULTS

The cumulative incidence rate of ALL was estimated at 21,315 per 100,000 Iranian children under 15 years of age. The value of Global Moran's I index was estimated 0.338 and significant (<0.001 P-value). Coldspots were observed in north and northwest of Iran and hotspots were identified in south, southwest and mid-east of Iran. In the present study, Max Temperature of Warmest Month (MTWM) and Direct Normal Irradiation (DNI) were risk factors and Precipitation of the Coldest Quarter (PCQ) and Altitude (AL) were protective factors in the incidence of ALL, even though the non-stationarity of local coefficients and local t-values was clear. GWPR, by capturing and applying spatial heterogeneity and spatial autocorrelation, had a greater performance and goodness of fit than GPR.

DISCUSSION

ALL has created spatial clusters in Iran. The incidence of ALL is the result of synergistic interaction between environmental, infectious, geographical and genetic risk factors. It is recommended to use of local models in ecological studies.

Identification of high-risk and low-risk clusters and estimation of the relative risk of acute lymphoblastic leukemia in provinces of Iran during 2006-2014 period: A geo-epidemiological study

BACKGROUND

The present study was conducted to determine the epidemiological status, identify high-risk and low-risk clusters, and estimate the relative risk (RR) of acute lymphoblastic leukemia (ALL) in provinces of Iran.

MATERIALS AND METHODS

This is an ecological study carried out using an Exploratory Multiple-Group design on 3769 children under 15 years of age with ALL from 2006 to 2014. Data analysis was performed using Mann-Whitney U, Global Moran's I and Kuldorff's purely spatial scan statistic tests at a significance level of 0.05.

RESULTS

The average annual incidence rate of ALL during 2006-2014 period was 2.25/100,000 children under 15 years of age. The most likely high-risk cluster with log-likelihood ratio (LLR) =327.47 is located in the southwestern part of Iran with a radius of 294.93 km and a centrality of 30.77 N and 50.83 E, which contained 1276 patients with a RR of 2.56. It includes Fars, Bushehr, Kohgiluyeh and Boyer-Ahmad, Khuzestan and Chahar Mahall and Bakhtiari provinces. On the other hand, the most likely low-risk cluster with 517 patients, and a RR 0.49 and LLR = 227.03 was identified in the northwestern part of Iran with a radius of 270.38 km and a centrality of 37.25 N and 49.49 E. It includes Zanjan, Qazvin, Gilan and East Azerbaijan, Ardabil, Alborz and Tehran provinces.

CONCLUSION

High-risk clusters were observed in Southwestern, central, and eastern Iran, while low-risk clusters were identified in Northern and Western Iran.

Childhood Leukemia in Small Geographical Areas and Proximity to Industrial Sources of Air Pollutants in Three Colombian Cities

Acute leukemia is the most common childhood cancer and has been associated with exposure to environmental carcinogens. This study aimed to identify clusters of acute childhood leukemia (ACL) cases and analyze their relationship with proximity to industrial sources of air pollution in three capital cities in Colombia during 2000-2015. Incident ACL cases were obtained from the population cancer registries for the cities of Bucaramanga, Cali, and Medellín. The inventory of industrial sources of emissions to the air was obtained from the regional environmental authorities and industrial conglomerates were identified. The Kulldorf's circular scan test was used to detect city clusters and to identify clusters around industrial conglomerates. Multivariable spatial modeling assessed the effect of distance and direction from the industrial conglomerates controlling for socioeconomic status. We identified industrials sectors within a buffer of 1 km around industrial conglomerates related to the ACL clusters. Incidence rates showed geographical heterogeneity with low spatial autocorrelation within cities. The spatio-temporal tests identified one cluster in each city. The industries located within 1 km around the ACL clusters identified in the three cities represent different sectors. Exposure to air pollution from industrial sources might be contributing to the incidence of ACL cases in urban settings in Colombia.

Temporal trend and spatial distribution of acute lymphoblastic leukemia in Iranian children during 2006-2014: a mixed ecological study

OBJECTIVES

The present study investigated the spatiotemporal epidemiological status of acute lymphoblastic leukemia (ALL), the most common childhood cancer, in Iran.

METHODS

Using an exploratory mixed design, this ecological study examined 3,769 under-15 children with ALL recorded in the National Cancer Registry of Iran during 2006-2014. Data were analyzed using the Mann-Whitney U test, the Getis-Ord general G (GOGG) index, optimized hot spot analysis, and Pearson correlation coefficients (PCC) at a significance level of 0.05.

RESULTS

The average annual incidence of the disease was 2.25 per 100,000 under-15 children, and the cumulative incidence rate (CIR) was 21.31 per 100,000 under-15 children. Patients' mean age was 5.90 years (standard deviation, 3.68), and the peak incidence was observed among 2-year to 5-year-olds. No significant difference was found in mean age between boys and girls (p=0.261). The incidence of ALL was more common during spring and summer than in other seasons. The GOGG index was 0.039 and significant (p<0.001). Hot spots were identified in south, central, and eastern Iran and cold spots in the north and west of Iran. The PCC between the CIR and latitude was negative (r=-0.507; p=0.003) but that between the CIR and longitude was positive (r=0.347; p=0.055).

CONCLUSIONS

The incidence of ALL in Iranian children was lower than that observed in developed countries, but showed an increasing trend. It can be argued that the incidence of ALL is due to synergistic interactions between environmental, infectious, geographical, and genetic risk factors.

Spatial-Temporal Cluster Analysis of Childhood Cancer in California

BACKGROUND

The observance of nonrandom space-time groupings of childhood cancer has been a concern of health professionals and the general public for decades. Many childhood cancers are suspected to have initiated in utero; therefore, we examined the spatial-temporal randomness of the birthplace of children who later developed cancer.

METHODS

We performed a space-time cluster analysis using birth addresses of 5,896 cases and 23,369 population-based, age-, sex-, and race/ethnicity-matched controls in California from 1997 to 2007, evaluating 20 types of childhood cancer and three a priori designated subgroups of childhood acute lymphoblastic leukemia (ALL). We analyzed data using a newly designed semiparametric analysis program, ClustR, and a common algorithm, SaTScan.

RESULTS

We observed evidence for nonrandom space-time clustering for ALL diagnosed at 2-6 years of age in the South San Francisco Bay Area (ClustR P = 0.04, SaTScan P = 0.07), and malignant gonadal germ cell tumors in a region of Los Angeles (ClustR P = 0.03, SaTScan P = 0.06). ClustR did not identify evidence of clustering for other childhood cancers, although SaTScan suggested some clustering for Hodgkin lymphoma (P = 0.09), astrocytoma (P = 0.06), and retinoblastoma (P = 0.06).

CONCLUSIONS

Our study provides evidence that childhood ALL diagnosed at 2-6 years and malignant gonadal germ cell tumors sporadically occurs in nonrandom space-time clusters. Further research is warranted to identify epidemiologic features that may inform the underlying etiology.

Exploring a potential mechanistic role of DNA methylation in the relationship between in utero and post-natal environmental exposures and risk of childhood acute lymphoblastic leukaemia

The aetiology of childhood acute lymphoblastic leukaemia (ALL) is unclear. Genetic abnormalities have been identified in a number of ALL cases, although these alone are not sufficient for leukaemic transformation. Various in utero and post-natal environmental exposures have been suggested to alter risk of childhood ALL. DNA methylation patterns can be influenced by environmental exposures, and are reported to be altered in ALL, suggesting a potential mediating mechanism between environment and ALL disease risk. To investigate this, we used a 'meet in the middle' approach, investigating the overlap between exposure-associated and disease-associated methylation change. Genome-wide DNA methylation changes in response to possible ALL-risk exposures (i.e. breast feeding, infection history, day care attendance, maternal smoking, alcohol, caffeine, folic acid, iron and radiation exposure) were investigated in a sub-population of the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort using an epigenome-wide association study (EWAS) approach (n = 861-927), and compared to a list of ALL disease-associated methylation changes compiled from published data. Hypergeometric probability tests suggested that the number of directionally concordant gene methylation changes observed in ALL disease and in response to the following exposures; maternal radiation exposure (p = 0.001), alcohol intake (p = 0.006); sugary caffeinated drink intake during pregnancy (p = 0.045); and infant day care attendance (p = 0.003), were not due to chance. Data presented suggests that DNA methylation may be one mediating mechanism in the multiple hit pathway needed for ALL disease manifestation.

Secondhand smoke: A new and modifiable prognostic factor in childhood acute lymphoblastic leukemias

BACKGROUND

The 5-year overall survival (OS) in childhood acute lymphoblastic leukemia (ALL) has reached 90% in high-income countries, levels that can no be longer overcome with strategies based on intensification of treatment. Other approaches in the search for new and modifiable prognostic factors are necessary to continue to improve these rates. The importance of environmental factors in the etiopathogenesis of childhood ALL has been regaining interest but its role in the prognosis and survival of this disease is not well explored. We aim to investigate the association between secondhand smoke (SHS) and survival in children diagnosed with ALL.

METHODS

We analyzed survival rates in 146 patients under the age of 15 years diagnosed with ALL between January 1998 and May 2016 in the Region of Murcia, Spain. Evaluation of parental SHS and other known prognostic factors (sex, age, white blood cell count at diagnosis, cytogenetics, NCI/Rome Criteria, early response to therapy, and relapse) were assessed for impact on OS, event-free survival (EFS), cumulative incidence of relapse (CIR), and treatment-related mortality (CITRM) using Kaplan-Meier analysis, Cox regression, and Fine-Gray model.

RESULTS

The mean follow-up time was 105.3 months (±66.5). Prenatal exposure to SHS due to parental smoking was highly prevalent. Of the mothers, 44.4% and 55.5% of the fathers smoked at some point during pregnancy. After the child's diagnosis of ALL 39.7% of mothers and 45.9% of fathers reported smoking. The Cox proportional hazards model showed that maternal smoking during pregnancy and after diagnosis (HR = 4.396, 95% CI: 1.173-16.474, p = 0.028); and relapse (HR = 7.919; 95% CI: 2.683-21.868; p < 0.001) are independent prognostic factors in determining survival. The Fine-Gray model showed that maternal smoking during pregnancy and after diagnosis (HR = 14.525, 95% CI: 4.228-49.90, p < 0.001) is an independent prognostic factor in CITRM.

CONCLUSIONS

Persistent SHS worsens OS and TRM in children with ALL. This negative impact contributes to a different prognosis and may possibly provide an exceptional insight into new therapeutic approaches, including environmental aspects such as prevention and smoking cessation to improve survival outcomes.