Genomics of racial and ethnic disparities in childhood acute lymphoblastic leukemia

Geographical variation in the incidence of childhood leukaemia in Manitoba

BACKGROUND

Identification of geographical areas and ecological factors associated with higher incidence of childhood leukaemias can direct further study for preventable factors and location of health services to manage such individuals.

AIM

The aim of this study was to describe the geographical variation and the socio-demographic factors associated with childhood leukaemia in Manitoba.

METHODS

Information on childhood leukaemia incidence between 1992 and 2008 was obtained from the Canadian Cancer Registry and the socio-demographic characteristics for the area of residence from the 2006 Canadian Census. Bayesian spatial Poisson mixed models were used to describe the geographical variation of childhood leukaemia and to determine the association between childhood leukaemia and socio-demographic factors.

RESULTS

The south-eastern part of the province had a higher incidence of childhood leukaemia than other parts of the province. In the age and sex-adjusted Poisson regression models, areas with higher proportions of visible minorities and immigrant residents had higher childhood leukaemia incidence rate ratios. In the saturated Poisson regression model, the childhood leukaemia rates were higher in areas with higher proportions of immigrant residents. Unemployment rates were not a significant factor in leukaemia incidence.

CONCLUSION

In Manitoba, areas with higher proportions of immigrants experience higher incidence rates of childhood leukaemia. We have identified geographical areas with higher incidence, which require further study and attention.

Racial/ethnic and socioeconomic disparities in survival among children with acute lymphoblastic leukemia in California, 1988-2011: A population-based observational study

BACKGROUND

Despite advances in treatment, survival from acute lymphoblastic leukemia (ALL) remains lower among non-White children than White children in the US. We investigated the association of race/ethnicity and socioeconomic status (SES) with survival.

PROCEDURES

We analyzed 9,295 Californian children (3,251 Whites, 4,890 Hispanics, 796 Asians, and 358 Blacks) aged ≤ 19 years diagnosed with a first primary ALL during 1988-2011. We used the Kaplan-Meier method to estimate survival at 1, 5, and 10 years after diagnosis for three calendar periods. Hazard ratios of death for race/ethnicity, SES, and clinical factors were estimated by Cox regression models.

RESULTS

Median follow-up time was 7.4 years (range 0-25 years). Over time, survival after ALL improved steadily, but inequalities persisted across races/ethnicities. Five-year survival (95% confidence interval) was 85.0% (83.6-86.2) for White, 81.4% (78.3-84.0) for Asian, 79.0% (77.8-80.2) for Hispanic, and 74.4% (69.4-78.8) for Black children. In multivariable-adjusted models, the hazard of death was increased by 57% among Black, 38% among Hispanic, and 33% among Asian children compared with White children. Patients residing in the lowest SES neighborhoods at diagnosis had a 39% increased risk of death relative to those living in higher SES neighborhoods.

CONCLUSION

Despite significant improvements in survival, non-White children and children residing in low SES neighborhoods experienced worse survival even after adjusting for potential confounders. Our findings highlight the need to capture specific information on disease biology, treatment, and treatment adherence to better understand the predictors of lower survival in minority and low SES groups.

High frequency and poor prognosis of late childhood BCR-ABL-positive and MLL-AF4-positive ALL define the need for advanced molecular diagnostics and improved therapeutic strategies in pediatric B-ALL in Pakistan

BACKGROUND

Fusion oncogenes (FOs) resulting from chromosomal abnormalities have an important role in leukemogenesis in pediatric B cell acute lymphoblastic leukemia (ALL). The most common FOs are BCR-ABL, MLL-AF4, ETV6-RUNX1, and TCF3-PBX1, all of which have important prognostic and drug selection implications. Moreover, frequencies of FOs have ethnic variations. We studied Pakistani frequencies of FOs, clinical pattern, and outcome in pediatric B-ALL.

METHODS

FOs were studied in 188 patients at diagnosis using reverse transcriptase-polymerase chain reaction (RT-PCR) and interphase fluorescent in situ hybridization (FISH). Data were analyzed using SPSS version 17 (SPSS Inc., Chicago, IL, USA).

RESULTS

FOs were detected in 87.2 % of patients. Mean overall survival was 70.9 weeks, 3-year survival was 31.9 %, and 3-year relapse-free survival was 18.1 %. Four patients died of drug toxicities. ETV6-RUNX1 (19.14 %) had better survival (110.9 weeks; p = 0.03); TCF3-PBX1 (2.1 %) was associated with inferior outcome and higher central nervous system (CNS) relapse risk; MLL-AF4 (18.1 %) was more common in the 8- to 15-year age group (24/34; p = 0.001) and was associated with organomegaly, low platelet count, and poor survival; and BCR-ABL (47.9 %) was associated with older age (7-15 years, 52/90), lower remission rates, shorter survival (43.73 ± 4.24 weeks) and higher white blood cell count. Overall, MLL-AF4 and BCR-ABL were detected in 66 % of B-ALL, presented in later childhood, and were associated with poor prognosis and inferior survival.

CONCLUSIONS

This study reports the highest ethnic frequency of BCR-ABL FO in pediatric ALL, and is consistent with previous reports from our region. Poor prognosis BCR-ABL and MLL-AF4 was detected in two-thirds of pediatric B-ALL and is likely to be the reason for the already reported poor survival of childhood ALL in South-East Asia. Furthermore, MLL-AF4, usually most common in infants, presented in later childhood in most of the ALL patients, which was one of the unique findings in our study. The results presented here highlight the need for mandatory inclusion of molecular testing for pediatric ALL patients in clinical decision making, together with the incorporation of tyrosine kinase inhibitors, as well as hematopoietic stem cell transplantation facilities, to improve treatment outcome for patients in developing countries.

Outcome of B-Cell Acute Lymphoblastic Leukemia in Brazilian Children: Immunophenotypical, Hematological, and Clinical Evaluation

The aim of this study is to investigate the clinical, hematological, and immunophenotypic characteristics of Brazilian children with B-cell acute lymphoblastic leukemia (B-ALL) to identify prognostic biomarkers of the disease. Thirty-three children newly diagnosed with B-ALL were followed between March 2004 and December 2009. Information about the demographic profile, diagnosis, immunophenotype, clinical manifestations, and disease outcome were gathered from the patients' medical records. Of the 33 patients with B-ALL, 18 were male and 15 female. Eighteen patients were classified as high risk; 13 as low risk, and 2 as true low risk. The frequencies of cluster of differentiation (CD)10, CD19, and CD20 antigens were 69.7%, 81.8%, and 18.2%, respectively. Six patients (18.2%) had aberrant expression of myeloid antigens. At diagnosis, patients immunopositive for CD20 had elevated white blood cell counts (P = 0.018) and lower platelet counts (P = 0.017). The 6-year overall survival was 67.5%± 3.47%. Our results demonstrate the distinct immunophenotypic and prognostic characteristics of patients with B-ALL, which can be related to the Brazilian racial admixture. Consequently, these results will most likely aid in the selection of additional prognostic markers and their use in monitoring the clinical manifestations and treatment response among B-ALL patients.

Association between CEBPE Variant and Childhood Acute Leukemia Risk: Evidence from a Meta-Analysis of 22 Studies

The CCAAT/enhancer binding proteins (CEBPs) have been involved in the etiology of acute leukemia (AL) and investigated in numerous genetic association studies, however, the results were inconclusive. The current meta-analysis was conducted to clarify the effect of CEBPE rs2239633 variant on childhood AL risk. Electronic literature search was performed on August 15, 2014, from databases of Medline, PubMed, Embase, and Web of Science. A total of 22 case-control studies were eligible for the pooled analysis. The results demonstrated that rs2239633 A allele was significantly associated with a decreased risk of childhood AL (A vs G: OR=0.87, 95%CI = 0.80, 0.94, p<0.001), especially in B-cell ALL subgroup (A vs G: OR = 0.79, 95%CI = 0.74, 0.83, p<0.001), but not among T-cell ALL or AML subgroups. In the stratified analysis by ethnicity, the association was observed in Europeans (A vs G: OR = 0.80, 95%CI = 0.76, 0.84, p<0.001) but not in Asian and mixed populations. Moreover, the results of sensitivity and cumulative meta-analysis indicated the robustness of our results. Also, Begg’s and Egger’s tests did not indicate any evidence of obvious asymmetry. In summary, our study provided evidence that CEBPE rs2239633 variant is associated with decreased risk of childhood B-cell ALL in Europeans.

Changes in cell death of peripheral blood lymphocytes isolated from children with acute lymphoblastic leukemia upon stimulation with 7 Hz, 30 mT pulsed electromagnetic field

Pulsed electromagnetic field (PEMF) influenced the viability of proliferating in vitro peripheral blood mononuclear cells (PBMCs) isolated from Crohn’s disease patients as well as acute myeloblastic leukemia (AML) patients by induction of cell death, but did not cause any vital changes in cells from healthy donors. Experiments with lymphoid U937 and monocytic MonoMac6 cell lines have shown a protective effect of PEMF on the death process in cells treated with death inducers.The aim of the current study was to investigate the influence of PEMF on native proliferating leukocytes originating from newly diagnosed acute lymphoblastic leukemia (ALL) patients.

The effects of exposure to PEMF were studied in PBMCs from 20 children with ALL. PBMCs were stimulated with three doses of PEMF (7 Hz, 30 mT) for 4 h each with 24 h intervals. After the last stimulation, the cells were double stained with annexin V and propidium iodide dye to estimate viability by flow cytometric analysis.The results indicated an increase of annexin V positive as well as double stained annexin V and propidium iodide positive cells after exposure to threefold PEMF stimulation.

A low-frequency pulsed electromagnetic field induces cell death in native proliferating cells isolated from ALL patients. The increased vulnerability of proliferating PBMCs to PEMF-induced interactions may be potentially applied in the therapy of ALL.The analysis of expression of apoptosis-related genes revealed changes in mRNA of some genes engaged in the intrinsic apoptotic pathway belonging to the Bcl-2 family and the pathway with apoptosis-inducing factor (AIF) abundance upon PEMF stimulation of PBMCs.

Perinatal and familial risk factors for acute lymphoblastic leukemia in a Swedish national cohort

BACKGROUND

Perinatal factors including high birth weight have been found to be associated with acute lymphoblastic leukemia (ALL) in case-control studies. However, to the best of our knowledge, these findings have seldom been examined in large population-based cohort studies, and the specific contributions of gestational age and fetal growth remain unknown.

METHODS

The authors conducted a national cohort study of 3,569,333 individuals without Down syndrome who were born in Sweden between 1973 and 2008 and followed for the incidence of ALL through 2010 (maximum age, 38 years) to examine perinatal and familial risk factors.

RESULTS

There were 1960 ALL cases with 69.7 million person-years of follow-up. After adjusting for potential confounders, risk factors for ALL included high fetal growth (incidence rate ratio [IRR] per additional 1 standard deviation, 1.07; 95% confidence interval [95% CI], 1.02-1.11 [P =.002]; and IRR for large vs appropriate for gestational age, 1.22; 95% CI, 1.06-1.40 [P =.005]), first-degree family history of ALL (IRR, 7.41; 95% CI, 4.60-11.95 [P<.001]), male sex (IRR, 1.20; 95% CI, 1.10-1.31 [P<.001]), and parental country of birth (IRR for both parents born in Sweden vs other countries, 1.13; 95% CI, 1.00-1.27 [P =.045]). These risk factors did not appear to vary by patient age at the time of diagnosis of ALL. Gestational age at birth, season of birth, birth order, multiple birth, parental age, and parental education level were not found to be associated with ALL.

CONCLUSIONS

In this large cohort study, high fetal growth was found to be associated with an increased risk of ALL in childhood through young adulthood, independent of gestational age at birth, suggesting that growth factor pathways may play an important long-term role in the etiology of ALL.

Inferior survival among Aboriginal children with cancer in Ontario

BACKGROUND

Pediatric cancer distribution and outcomes have not been examined in Canadian Aboriginal children. The objective of this study was to describe the distribution, event-free survival, and overall survival of Aboriginal children with malignancies who reside in Ontario compared with non-Aboriginal children.

METHODS

This population-based study included 10,520 Ontario children (aged <18 years) who were diagnosed with cancer between 1985 and 2011. Patients were identified from the Pediatric Oncology Group of Ontario Networked Information System database. Aboriginal children were identified by self-reported ethnicity or postal code on a Native reserve at diagnosis. Descriptive statistics of the patients were presented and compared using the Fisher exact test. Event-free and overall survival probabilities were calculated for Aboriginal and non-Aboriginal children, described using Kaplan-Meier curves, and compared using log-rank tests.

RESULTS

In total, 65 Aboriginal children and 10,364 non-Aboriginal children with malignancy were identified. The distribution of malignancy type was similar between the 2 groups. There were no significant differences in baseline characteristics, presence of metastatic disease, or treatment approach (clinical trial, standard of care, or individualized protocol) between the groups. The 5e-year event-free survival rate (± standard error) was 56.3% ± 6.2% among Aboriginal children versus 72.8% ± 0.4% among non-Aboriginal children (P = .0042), and the 5-year overall survival rate was 64% ± 6.0% versus 79.3 ± 0.4% (P = .0017), respectively. The cause of death did not vary according to Aboriginal ethnicity.

CONCLUSIONS

Survival was significantly inferior among Aboriginal children who had cancer compared with non-Aboriginal children who had cancer in Ontario. Future studies are required to define the etiology of this disparity, evaluate the issue nationally, and create interventions to improve outcomes for Aboriginal children.