Mode of Delivery and Risk of Childhood Leukemia

The genetic risk of acute lymphoblastic leukemia and its implications for children of Latin American origin

Acute lymphoblastic leukemia (ALL) is the most common cancer in children, and disproportionately affects children of Hispanic/Latino ethnicity in the United States, who have the highest incidence of disease compared with other racial/ethnic groups. Incidence of childhood ALL is similarly high in several Latin American countries, notably in Mexico, and of concern is the rising incidence of childhood ALL in some Hispanic/Latino populations that may further widen this disparity. Prior studies have implicated common germline genetic variants in the increased risk of ALL among Hispanic/Latino children. In this review, we describe the known disparities in ALL incidence as well as patient outcomes that disproportionately affect Hispanic/Latino children across the Americas, and we focus on the role of genetic variation as well as Indigenous American ancestry in the etiology of these disparities. Finally, we discuss future avenues of research to further our understanding of the causes of the disparities in ALL incidence and outcomes in children of Latin American origin, which will be required for future precision prevention efforts.

Early Life Nutrition Factors and Risk of Acute Leukemia in Children: Systematic Review and Meta-Analysis

Acute leukemia commonly occurs in young children with peak incidence at the age of 2-5 years. However, the etiology is still unclear and many preventable risk factors still deserve to be reviewed. The focus of this systematic review and meta-analysis is to summarize the evidence concerning early life nourishment (breastfeeding, early life diet), neonatal vitamin K administration and the risk of acute leukemia. All epidemiological studies published up to June 2023 and assessing diet-related risk factors for childhood acute leukemia were identified in two electronic databases (PubMed and Web of Science), with no limits on publication year or language. A total of 38 studies (37 case-control studies and 1 study with pooled analysis) were included. The published risk estimates were combined into a meta-analysis using the Generic Inverse Variance method. The current evidence shows that breastfeeding (yes vs. no) has a protective effect against acute lymphoblastic leukemia (odds ratio = 0.85; 95% CI, 0.76-0.94). Evidence related to the role of other studied factors (foods and supplements) is inconclusive. Further research into the potential role of diet in early life and the risk of acute leukemia is needed to develop prevention strategies at population level. Review Registration: PROSPERO registration no. CRD42019128937.

28-year incidence and time trends of childhood leukaemia in former East Germany compared to West Germany after German reunification: A study from the German Childhood Cancer Registry

BACKGROUND

The aetiology of childhood leukaemia is largely unknown. Analyses of geographical differences may enhance aetiologic insights. The reunification of Germany in 1990 provides a unique opportunity to evaluate incidence patterns and time trends in two merging countries with substantial lifestyle, social and socioeconomic differences. With this study we provide an extensive assessment of 28-year incidence patterns and temporal trends after the German reunification.

METHODS

We identified all children diagnosed with a lymphoid leukaemia (LL) or acute myeloid leukaemia (AML) before the age of 15 years between 1991 and 2018 using the German Childhood Cancer Registry (N = 14,922), and evaluated the incidence pattern and temporal trends in former East Germany compared to West Germany by subtype, age at diagnosis and sex.

RESULTS

Incidence rates of LL were substantially lower (around 20 %) in Eastern Germany compared to Western Germany at the time of reunification. This was followed by a remarkable increase in Eastern Germany across both sexes and age groups until around 2000, when incidence rates reached the same levels as those in Western German federal states. Thereafter, incidence rates remained rather stable with some indications of a slightly decreasing tendency in both Eastern and Western Germany (estimated annual percentage changes (EAPC) 2005-2018: East Germany = -0.8 %; West Germany = -0.4 %), driven by the 0- to 4-year olds. Overall, AML incidence rates were stable over time in Western Germany, while EAPC for Eastern Germany indicated an increasing tendency (EAPC 1991-2018 = 1.3 %) driven by the older children, mostly during the early 2000s and in most recent years.

CONCLUSION

The underlying mechanisms driving the childhood leukaemia rates remain inconclusive. Linkage studies including individual and clinical data would be valuable in evaluating the impact of a population's social, socioeconomic and lifestyle changes on the risk of childhood leukaemia and disease aetiology overall.

Cesarean Section Is Associated with an Increased Risk of Acute Lymphoblastic Leukemia and Hepatoblastoma in Children from Minnesota

BACKGROUND

In recent decades, Cesarean section (C-section) rates have increased. C-section is hypothesized to negatively impact the developing immune system by altering activation of the hypothalamic-pituitary-adrenal axis and the infant microbiome, among other mechanisms, thereby potentially modulating childhood cancer risk.

METHODS

Using linked birth and cancer registry data from Minnesota (1976-2014), we included individuals ages 0-14 at diagnosis with one of 19 cancers. Cases and controls were frequency matched by birth year. We used logistic regression to estimate ORs and 95% confidence intervals (95% CI) as the measure of association between C-section and cancer. We assessed sex-C-section interactions for each cancer and conducted stratified analyses in acute lymphoblastic leukemia (ALL) for birth year, age at diagnosis, and maternal race.

RESULTS

There were 3,166 cases and 20,589 controls. One third (n = 1,174) of controls born during 2004-2014 were delivered via C-section compared with 42.2% of cases (n = 285). C-section was associated with ALL (n = 819; OR: 1.20; 95% CI: 1.01-1.43) and hepatoblastoma (n = 50; OR: 1.89; 95% CI: 1.03-3.48), particularly among females (ALL OR: 1.34; 95% CI: 1.04-1.72; hepatoblastoma OR: 3.87; 95% CI: 1.30-11.57). The risk of ALL was highest during 2005-2014 (OR: 1.62; 95% CI: 1.11-2.34) and among children ages 1-5 years (OR: 1.28; 95% CI: 1.02-1.61).

CONCLUSIONS

C-section was associated with an increased risk of ALL and hepatoblastoma.

IMPACT

These associations require investigation to determine causality and rule out confounding by indication or reverse causality. The mechanisms underlying these associations may depend on neonatal immune system processes altered during C-section deliveries.

Cancer health disparities in racial/ethnic minorities in the United States

There are well-established disparities in cancer incidence and outcomes by race/ethnicity that result from the interplay between structural, socioeconomic, socio-environmental, behavioural and biological factors. However, large research studies designed to investigate factors contributing to cancer aetiology and progression have mainly focused on populations of European origin. The limitations in clinicopathological and genetic data, as well as the reduced availability of biospecimens from diverse populations, contribute to the knowledge gap and have the potential to widen cancer health disparities. In this review, we summarise reported disparities and associated factors in the United States of America (USA) for the most common cancers (breast, prostate, lung and colon), and for a subset of other cancers that highlight the complexity of disparities (gastric, liver, pancreas and leukaemia). We focus on populations commonly identified and referred to as racial/ethnic minorities in the USA-African Americans/Blacks, American Indians and Alaska Natives, Asians, Native Hawaiians/other Pacific Islanders and Hispanics/Latinos. We conclude that even though substantial progress has been made in understanding the factors underlying cancer health disparities, marked inequities persist. Additional efforts are needed to include participants from diverse populations in the research of cancer aetiology, biology and treatment. Furthermore, to eliminate cancer health disparities, it will be necessary to facilitate access to, and utilisation of, health services to all individuals, and to address structural inequities, including racism, that disproportionally affect racial/ethnic minorities in the USA.

Cesarean section and risk of childhood leukemia: a systematic review and meta-analysis

BACKGROUND

A large number of studies pointed that being delivered by cesarean section (CS) would affect the health outcomes of offspring, however, whether CS would affect the risk of childhood leukemia remained uncertain. This study conducted a meta-analysis to quantitatively evaluate whether being delivered by CS would influence the onset of childhood leukemia.

METHODS

PubMed, Embase and Web of Science databases were searched from 3rd June, 1950 to 13th October, 2019 to identify the literature, which examined the relationship between CS and childhood leukemia. This study used Newcastle-Ottawa Scale to assess the quality of literature. Subgroup analyses were conducted on region, mode of delivery, design of the study and number of confounders adjusted. Egger's test and Begg's test were performed to evaluate possible publication bias.

RESULTS

The pooled odds ratio (OR) estimates illustrated that children delivered by CS had a higher risk of developing leukemia [OR 1.10, 95% confidence interval (CI) 1.04-1.17, P = 0.002] and lymphoblastic leukemia (OR 1.12, 95% CI 1.03-1.23, P = 0.009), while a significant association for myeloid leukemia was not observed (OR 1.05, 95% CI 0.92-1.20, P = 0.451). Results of subgroup analyses indicated that elective CS would increase the risk of childhood lymphoblastic leukemia (OR 1.16, 95% CI 1.06-1.27, P = 0.002). However, a statistical relationship between emergency CS and lymphoblastic leukemia was not observed (OR 1.07, 95% CI 0.93-1.23, P = 0.364).

CONCLUSIONS

CS would increase the risk of childhood lymphoblastic leukemia. It is worth noting that subgroup analyses shows that elective CS rather than emergency CS increases the risk of lymphoblastic leukemia in offspring.

New Insights into Molecular Links Between Microbiota and Gastrointestinal Cancers: A Literature Review

Despite decades of exhaustive research on cancer, questions about cancer initiation, development, recurrence, and metastasis have still not been completely answered. One of the reasons is the plethora of factors acting simultaneously in a tumour microenvironment, of which not all have garnered attention. One such factor that has long remained understudied and has only recently received due attention is the host microbiota. Our sheer-sized microbiota exists in a state of symbiosis with the body and exerts significant impact on our body's physiology, ranging from immune-system development and regulation to neurological and cognitive development. The presence of our microbiota is integral to our development, but a change in its composition (microbiota dysbiosis) can often lead to adverse effects, increasing the propensity of serious diseases like cancers. In the present review, we discuss environmental and genetic factors that cause changes in microbiota composition, disposing of the host towards cancer, and the molecular mechanisms (such as β-catenin signalling) and biochemical pathways (like the generation of oncogenic metabolites like N-nitrosamines and hydrogen sulphide) that the microbiota uses to initiate or accelerate cancers, with emphasis on gastrointestinal cancers. Moreover, we discuss how microbiota can adversely influence the success of colorectal-cancer chemotherapy, and its role in tumour metastasis. We also attempted to resolve conflicting results obtained for the butyrate effect on tumour suppression in the colon, often referred to as the 'butyrate paradox'. In addition, we suggest the development of microbiota-based biomarkers for early cancer diagnosis, and a few target molecules of which the inhibition can increase the overall chances of cancer cure.

Paediatric acute lymphoblastic leukaemia and caesarean section: A report from the United Kingdom Childhood Cancer Study (UKCCS)

BACKGROUND

Reports have suggested that children born by caesarean initiated before labour onset may be at increased risk of developing acute lymphoblastic leukaemia (ALL). However, with most data being derived from case-control study interviews, information on the underpinning reasons for caesarean section is sparse, and evidence is conflicting.

OBJECTIVES

Use clinical records compiled at the time of delivery to investigate the association between childhood ALL and caesarean delivery; examining timing in relation to labour onset, and reasons for the procedure.

METHODS

Data are from the UK Childhood Cancer Study, a population-based case-control study conducted in the 1990s, when caesarean section rates were relatively low, in England, Scotland, and Wales. Children with ALL were individually matched to two controls on sex, date of birth, and region of residence. Information on mode of delivery and complications was abstracted from obstetric records. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using logistic regression models adjusted for matching variables and relevant covariates.

RESULTS

Around 75% of the 1034 cases and 1914 controls were born through unassisted vaginal delivery. Caesarean delivery was as frequent in cases and controls (OR 1.07, 95% CI 0.84, 1.36). No association was observed between ALL and caesarean delivery either during or before labour, with adjusted ORs of 1.08 (95% CI 0.78, 1.48) and 1.09 (95% CI 0.78, 1.53), respectively. For B-cell ALL, the ORs were 1.14 (95% CI 0.81, 1.59) for caesarean during labour and 1.21 (95% CI 0.85, 1.72) for prelabour. The underpinning reasons for caesarean delivery differed between cases and controls; with preeclampsia, although very rare, being more common amongst cases born by caesarean (OR 8.91, 95% CI 1.48, 53.42).

CONCLUSIONS

Our obstetric record-based study found no significant evidence that caesarean delivery increased the risk of childhood ALL, either overall or when carried out before labour.

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.

Allergies and Childhood Acute Lymphoblastic Leukemia: A Case-Control Study and Meta-analysis

Background: Allergic disease is suspected to play a role in the development of childhood acute lymphoblastic leukemia (ALL). Studies conducted over the last several decades have yielded mixed results.Methods: We examined the association between allergy, a common immune-mediated disorder, and ALL in the California Childhood Leukemia Study (CCLS), a case-control study of 977 children diagnosed with ALL and 1,037 matched controls (1995-2015). History of allergies in the first year of life was obtained from interviews, mainly reported by mothers. Logistic regression analyses were conducted to estimate ORs and 95% confidence intervals (CIs), controlling for birth order, daycare attendance, and mode of delivery. In addition, we conducted meta-analyses with data from the CCLS and 12 published studies and employed a new method to estimate between-study heterogeneity (R_b).Results: Overall, no associations were observed between childhood ALL risk and specific allergy phenotypes or any allergy, as a group. However, having any allergy was associated with an increased risk of ALL among the youngest study participants. In the meta-analysis random-effects models, reduced odds of ALL were associated with hay fever (metaOR = 0.65; 95% CI, 0.47-0.90); however, restricting the analysis to studies that used medical records for assessment of allergy or recently published studies led to null or attenuated results.Conclusions: Overall, our findings do not support a clear association between allergy and childhood ALL.Impact: The degree to which epidemiologic studies can inform the relationship between allergies and risk of childhood ALL is limited by R_b. Cancer Epidemiol Biomarkers Prev; 27(10); 1142-50. ©2018 AACR.

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSIONS

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

Cesarean Delivery and Risk of Infant Leukemia: A Report from the Children's Oncology Group

Background: Studies have reported increased risks of pediatric acute lymphoblastic leukemia (ALL) among children born by cesarean delivery (CD). However, no previous study has examined the impact of CD on risk of infant leukemia specifically.Methods: In this study, 443 infants diagnosed with acute leukemia, including both ALL and acute myelogenous leukemia (AML), were identified at Children's Oncology Group institutions between January 1996 and December 2006; 324 controls frequency matched by year of birth were identified though random digit dialing and random selection from U.S. birth registries. Using interview data and, for a subset of participants, medical record data, we analyzed CD overall and by indications that likely resulted in pre-labor CD (PLCD) or emergency CD (ECD). Odds ratios (ORs) and 95% confidence intervals (CIs) for risk of ALL and AML were estimated using multivariable unconditional logistic regression models, adjusted for year of birth, birth weight, and maternal race.Results: We observed an increased point estimate for the association between CD and ALL (OR, 1.52 and 95% CI, 1.02-2.25). We did not observe an association between CD and AML (OR, 1.02 and 95% CI, 0.64-1.62). In analyses of indication for CD, we observed elevated effect estimates for the associations of both PLCD and ECD and infant ALL.Conclusions: Our analysis suggests an increased risk of infant ALL following CD, including both PLCD and ECD. Altered microbiota colonization may be involved in development of leukemia in infants, but clear biological mechanisms have yet to be determined.Impact: This study provides the first in-depth examination of CD and infant leukemia. Cancer Epidemiol Biomarkers Prev; 27(4); 473-8. ©2018 AACR.

Mother and child characteristics at birth and early age leukemia: a case-cohort population-based study

OBJECTIVE

The population-based cancer registries (PBCR) and the Information System on Live Births in Brazil (Sistema de Informações sobre Nascidos Vivos [SINASC]) have information that enables the test for risk factors associated with leukemia at an early age. The aim of this study was to identify maternal and birth characteristics associated with early-age acute leukemia (EAL) in Brazil.

METHODS

A case-cohort study was performed using secondary dataset information of PBCR and SINASC. The risk association variables were grouped into (i) characteristics of the child at birth and (ii) characteristics of maternal exposure during pregnancy. The case-control ratio was 1:4. Linkage was performed using R software; odds ratio (OR) and 95% confidence interval (CI) were calculated by logistic regression models.

RESULTS

EAL was associated with maternal occupational exposure to chemicals (agricultural, chemical, and petrochemical industry; adjOR: 2.18, 95% CI: 1.16-4.10) and with birth defects (adjOR: 3.62, 95% CI: 1.19-11.00).

CONCLUSIONS

The results of this study, with the identification of EAL risk factors in population-based case-cohort study, strengthen the knowledge and improve databases, contributing to investigations on risk factors associated with childhood leukemia worldwide.

Cesarean Section and Risk of Childhood Acute Lymphoblastic Leukemia in a Population-Based, Record-Linkage Study in California

The relationship of mode of delivery to risk of childhood acute lymphoblastic leukemia (ALL) is uncertain. After linking birth records and cancer registry data from California, we conducted a population-based case-control study to investigate the role of delivery by cesarean section (C-section) in the etiology of childhood ALL. This study included 5,081 cases and 18,927 matched controls born in 1978-2009; more detailed data were available on type of C-section (i.e., elective vs. emergency) for a subset of 1,552 cases and 5,688 controls. No association was observed between C-section overall and childhood ALL risk (<15 years of age), but elective C-section was associated with a significantly elevated risk of ALL (odds ratio (OR) = 1.17, 95% confidence interval (CI): 1.01, 1.36). At the peak ages of ALL incidence (2-4 years), C-section was associated with an 11% higher risk of ALL (OR = 1.11, 95% CI: 1.01, 1.22) compared with vaginal delivery, and the magnitude of the association was larger for elective C-section (OR = 1.38, 95% CI: 1.11, 1.70). Emergency C-section was not associated with childhood ALL. Because of design features minimizing nonparticipation and inaccurate recall, this record linkage-based study is less prone to bias. Our results suggest that delivery by elective C-section was associated with a higher risk of childhood ALL, especially at the peak ages of incidence. It is important to evaluate possible mechanisms, because this potential risk factor is modifiable.

In utero cytomegalovirus infection and development of childhood acute lymphoblastic leukemia

It is widely suspected, yet controversial, that infection plays an etiologic role in the development of acute lymphoblastic leukemia (ALL), the most common childhood cancer and a disease with a confirmed prenatal origin in most cases. We investigated infections at diagnosis and then assessed the timing of infection at birth in children with ALL and age, gender, and ethnicity matched controls to identify potential causal initiating infections. Comprehensive untargeted virome and bacterial analyses of pretreatment bone marrow specimens (n = 127 ALL in comparison with 38 acute myeloid leukemia cases in a comparison group) revealed prevalent cytomegalovirus (CMV) infection at diagnosis in childhood ALL, demonstrating active viral transcription in leukemia blasts as well as intact virions in serum. Screening of newborn blood samples revealed a significantly higher prevalence of in utero CMV infection in ALL cases (n = 268) than healthy controls (n = 270) (odds ratio [OR], 3.71, confidence interval [CI], 1.56-7.92, P = .0016). Risk was more pronounced in Hispanics (OR=5.90, CI=1.89-25.96) than in non-Hispanic whites (OR=2.10 CI= 0.69-7.13). This is the first study to suggest that congenital CMV infection is a risk factor for childhood ALL and is more prominent in Hispanic children. Further investigation of CMV as an etiologic agent for ALL is warranted.

Maternal and Birth Characteristics and Childhood Embryonal Solid Tumors: A Population-Based Report from Brazil

BACKGROUND

Several maternal and birth characteristics have been reported to be associated with an increased risk of many childhood cancers. Our goal was to evaluate the risk of childhood embryonal solid tumors in relation to pre- and perinatal characteristics.

METHODS

A case-cohort study was performed using two population-based datasets, which were linked through R software. Tumors were classified as central nervous system (CNS) or non-CNS-embryonal (retinoblastoma, neuroblastoma, renal tumors, germ cell tumors, hepatoblastoma and soft tissue sarcoma). Children aged <6 years were selected. Adjustments were made for potential confounders. Odds ratios (OR) with 95% confidence intervals (CI) were computed by unconditional logistic regression analysis using SPSS.

RESULTS

Males, high maternal education level, and birth anomalies were independent risk factors. Among children diagnosed older than 24 months of age, cesarean section (CS) was a significant risk factor. Five-minute Apgar ≤8 was an independent risk factor for renal tumors. A decreasing risk with increasing birth order was observed for all tumor types except for retinoblastoma. Among children with neuroblastoma, the risk decreased with increasing birth order (OR = 0.82 (95% CI 0.67-1.01)). Children delivered by CS had a marginally significantly increased OR for all tumors except retinoblastoma. High maternal education level showed a significant increase in the odds for all tumors together, CNS tumors, and neuroblastoma.

CONCLUSION

This evidence suggests that male gender, high maternal education level, and birth anomalies are risk factors for childhood tumors irrespective of the age at diagnosis. Cesarean section, birth order, and 5-minute Apgar score were risk factors for some tumor subtypes.

Environmental, maternal, and reproductive risk factors for childhood acute lymphoblastic leukemia in Egypt: a case-control study

BACKGROUND

Acute lymphocytic leukemia (ALL) is the most common pediatric cancer. The exact cause is not known in most cases, but past epidemiological research has suggested a number of potential risk factors. This study evaluated associations between environmental and parental factors and the risk for ALL in Egyptian children to gain insight into risk factors in this developing country.

METHODS

We conducted a case-control design from May 2009 to February 2012. Cases were recruited from Children's Cancer Hospital, Egypt (CCHE). Healthy controls were randomly selected from the general population to frequency-match the cumulative group of cases by sex, age groups (<1; 1 - 5; >5 - 10; >10 years) and region of residence (Cairo metropolitan region, Nile Delta region (North), and Upper Egypt (South)). Mothers provided answers to an administered questionnaire about their environmental exposures and health history including those of the father. Odds ratios (ORs) and 95 % confidence intervals (CI) were calculated using logistic regression with adjustment for covariates.

RESULTS

Two hundred ninety nine ALL cases and 351 population-based controls frequency-matched for age group, gender and location were recruited. The risk of ALL was increased with the mother's use of medications for ovulation induction (ORadj = 2.5, 95 % CI =1.2 -5.1) and to a lesser extend with her age (ORadj = 1.8, 95 % CI = 1.1 - 2.8, for mothers ≥ 30 years old). Delivering the child by Cesarean section, was also associated with increased risk (ORadj = 2.01, 95 % CI =1.24-2.81).

CONCLUSIONS

In Egypt, the risk for childhood ALL appears to be associated with older maternal age, and certain maternal reproductive factors.

Maternal prenatal intake of one-carbon metabolism nutrients and risk of childhood leukemia

PURPOSE

Folate, vitamins B12 and B6, riboflavin, and methionine are critical nutrients for the one-carbon metabolism cycle involved in DNA synthesis and epigenetic processes. We examined the association between maternal intake of these nutrients before pregnancy and risk of childhood acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) in a matched case-control study.

METHODS

Maternal dietary intake and vitamin supplement use in the year before pregnancy was assessed by food frequency questionnaire for 681 ALL cases, 103 AML cases, and 1076 controls. Principal component analysis was used to construct a variable representing combined nutrient intake, and conditional logistic regression estimated the odds ratio (OR) and 95% confidence interval (CI) for the association of ALL and AML with the principal component and each nutrient.

RESULTS

Higher maternal intake of one-carbon metabolism nutrients from food and supplements combined was associated with reduced risk of ALL (OR for one-unit change in the principal component = 0.91, CI 0.84-0.99) and possibly AML (OR for the principal component = 0.83, CI 0.66-1.04). When analyzed separately, intake of supplements high in these nutrients was associated with a reduced risk of ALL in children of Hispanic women only.

CONCLUSIONS

In conclusion, these data suggest that higher maternal intake of one-carbon metabolism nutrients may reduce risk of childhood leukemia.

Caesarean delivery and risk of childhood leukaemia: a pooled analysis from the Childhood Leukemia International Consortium (CLIC)

BACKGROUND

Results from case-control studies have shown an increased risk of acute lymphoblastic leukaemia (ALL) in young children born by caesarean delivery, and prelabour caesarean delivery in particular; however, an association of method of delivery with childhood leukaemia subtypes has yet to be established. We therefore did a pooled analysis of data to investigate the association between childhood leukaemia and caesarean delivery.

METHODS

We pooled data from 13 case-control studies from the Childhood Leukemia International Consortium done in nine countries (Canada, Costa Rica, Egypt, France, Germany, Greece, Italy, New Zealand, and the USA) for births from 1970-2013. We analysed caesarean delivery overall and by indications that probably resulted in prelabour caesarean delivery or emergency caesarean delivery. We used multivariable logistic regression models, adjusted for child's birthweight, sex, age, ethnic origin, parental education, maternal age, and study, to estimate odds ratios (ORs) and 95% CIs for the risk of ALL and acute myeloid leukaemia (AML) in children aged 0-14 years at diagnosis.

FINDINGS

The studies provided data for 8780 ALL cases, 1332 AML cases, and 23 459 controls, of which the birth delivery method was known for 8655 (99%) ALL cases, 1292 (97%) AML cases, and 23 351 (>99%) controls. Indications for caesarean delivery were available in four studies (there were caesarean deliveries for 1061 of 4313 ALL cases, 138 of 664 AML cases, and 1401 of 5884 controls). The OR for all indications of caesarean delivery and ALL was 1·06 (95% CI 0·99-1·13), and was significant for prelabour caesarean delivery and ALL (1·23 [1·04-1·47]; p=0·018). Emergency caesarean delivery was not associated with ALL (OR 1·02 [95% CI 0·81-1·30]). AML was not associated with caesarean delivery (all indications OR 0·99 [95% CI 0·84-1·17]; prelabour caesarean delivery 0·83 [0·54-1·26]; and emergency caesarean delivery 1·05 [0·63-1·77]).

INTERPRETATION

Our results suggest an increased risk of childhood ALL after prelabour caesarean delivery. If this association is causal, maladaptive immune activation due to an absence of stress response before birth in children born by prelabour caesarean delivery could be considered as a potential mechanism.

FUNDING

National Cancer Institute.

Role of glutathione S-transferase M1, T1 and P1 gene polymorphisms in childhood acute lymphoblastic leukemia susceptibility in a Turkish population

The variations between different individuals in the xenobiotic metabolizing enzymes' activity were shown to modify susceptibility to childhood acute lymphoblastic leukemia (ALL). Polymorphisms associated with genes coding for the glutathione S-transferase (GST) enzyme were known to affect the metabolism of different carcinogens. The aim of this study was to evaluate the influence of the GSTM1 and GSTT1 deletion polymorphisms, and the GSTP1 Ile105Val single nucleotide polymorphism (SNP) on the susceptibility to childhood ALL. The study was conducted in 95 children with ALL and 190 healthy control subjects from the Turkish population. The data revealed no difference in the prevalence of the GSTM1 and GSTT1 null genotypes between the childhood ALL patients and the controls. No association was found between GSTP1 Ile105Val variants and the susceptibility to childhood ALL, separately or in combination. Our findings suggested that the status of heritable GST polymorphism might not influence the risk of developing childhood ALL. Studies with a larger sample size are needed to evaluate and confirm the validity of our results.

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There was no association between any of the GST variants and the risk of childhood ALL in Turkish Population

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The alleles of GST P1 were similar in cases and controls for childhood ALL

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There was not statistically significant relationship between the combined GSTM1, GSTP1, and GSTT1 genotypes and the risk of childhood ALL

Childhood acute lymphoblastic leukaemia and indicators of early immune stimulation: the Estelle study (SFCE)

Background:

Factors related to early stimulation of the immune system (breastfeeding, proxies for exposure to infectious agents, normal delivery, and exposure to animals in early life) have been suggested to decrease the risk of childhood acute lymphoblastic leukaemia (ALL).

Methods:

The national registry-based case–control study, ESTELLE, was carried out in France in 2010–2011. Population controls were frequency matched with cases on age and gender. The participation rates were 93% for cases and 86% for controls. Data were obtained from structured telephone questionnaires administered to mothers. Odds ratios (OR) were estimated using unconditional regression models adjusted for age, gender, and potential confounders.

Results:

In all, 617 ALL and 1225 controls aged ⩾1 year were included. Inverse associations between ALL and early common infections (OR=0.8, 95% confidence interval (CI): 0.6, 1.0), non-first born (⩾3 vs 1; OR=0.7, 95% CI: 0.5, 1.0), attendance of a day-care centre before age 1 year (OR=0.7, 95% CI: 0.5, 1.0), breastfeeding (OR=0.8, 95% CI: 0.7, 1.0), and regular contact with pets (OR=0.8, 95% CI: 0.7, 1.0) in infancy were observed.

Conclusions:

The results support the hypothesis that conditions promoting the maturation of the immune system in infancy have a protective role with respect to ALL.