Clues to the etiology of childhood brain cancer: N-nitroso compounds, polyomaviruses, and other factors of interest

Seasonality of main childhood embryonal tumours and rhabdomyosarcoma, France, 2000-2015

Few studies have investigated the seasonal patterns of embryonal tumours. Based on data from the French National Registry of Childhood Cancers, the present study aimed to investigate seasonal variations in embryonal tumour incidence rates by month of birth and by month of diagnosis. The study included 6635 primary embryonal tumour cases diagnosed before the age of 15 years over the period 2000-2015 in mainland France. Assuming monthly variations in incidence rates were homogeneous over 2000-2015, we used a Poisson regression model to test for overall heterogeneity in standardised incidence ratios (SIRs) by month of birth or diagnosis. The seasonal scan statistic method was used to detect monthly excesses or deficits of embryonal tumour cases over the whole study period. The annual reproducibility of the observed monthly variations was formally tested. An overall heterogeneity in incidence rates by month of birth was observed for rhabdomyosarcoma in boys only. Based on the month of diagnosis, a seasonality was evidenced for unilateral retinoblastoma, with a lower incidence rate in the summer (SIR_Jul-Aug  = 0.68, 95% CI = 0.52-0.87), whilst the incidence rate of rhabdomyosarcoma tended to be lower in August (SIR_Aug  = 0.68, 95% CI = 0.52-0.89). No seasonality was detected for the other embryonal tumour groups by month of birth or month of diagnosis. This study is one of the largest to have investigated the seasonality of childhood embryonal tumours. The study showed a seasonal variation in the incidence rates by month of diagnosis for unilateral retinoblastoma and rhabdomyosarcoma. Our findings are likely to reflect a delay in consultation during the summer months. However, the role of seasonally varying environmental exposures cannot be ruled out.

Perinatal and early life risk factors for childhood brain tumors: Is instrument-assisted delivery associated with higher risk?

BACKGROUND

The childhood peak of brain tumors suggests that early-life exposures might have a role in their etiology. Hence, we examined in the Greek National Registry for Childhood Hematological Malignancies and Solid tumors (NARECHEM-ST) whether perinatal and early-life risk factors influence the risk of childhood brain tumors.

METHODS

In a nationwide case-control study, we included 203 cases (0-14 years) with a diagnosis of brain tumor in NARECHEM-ST (2010-2016) and 406 age-, sex-, and center-matched hospital controls. Information was collected via interviews with the guardians and we analyzed the variables of interest in multivariable conditional logistic regression models.

RESULTS

Instrument-assisted delivery was associated with higher (OR: 7.82, 95%CI: 2.18-28.03), whereas caesarean delivery with lower (OR: 0.67, 95%CI: 0.45-0.99) risk of childhood brain tumors, as compared to spontaneous vaginal delivery. Maternal alcohol consumption during pregnancy (OR: 2.35, 95%CI: 1.45-3.81) and history of living in a farm (OR: 4.98, 2.40-10.32) increased the odds of childhood brain tumors. Conversely, higher birth order was associated with lower risk (OR for 2nd vs. 1st child: 0.60, 95%CI: 0.40-0.89 and OR for 3^rd vs. 1^st: 0.34, 95%CI: 0.18-0.63). Birth weight, gestational age, parental age, history of infertility, smoking during pregnancy, allergic diseases, and maternal diseases during pregnancy showed no significant associations.

CONCLUSIONS

Perinatal and early-life risk factors, and specifically indicators of brain trauma, exposure to toxic agents and immune system maturation, might be involved in the pathogenesis of childhood brain tumors. Larger studies should aim to replicate our findings and examine associations with tumor subtypes.

Prenatal and Postnatal Medical Conditions and the Risk of Brain Tumors in Children and Adolescents: An International Multicenter Case-Control Study

BACKGROUND

Previous studies have evaluated the effect of medical diagnostic radiation on brain tumors. Recent cohort studies have reported an increased risk associated with exposure to head CT scans.

METHODS

Information regarding medical conditions, including prenatal and postnatal exposure to medical diagnostic radiation, was obtained from CEFALO, a multicenter case-control study performed in Denmark, Norway, Sweden, and Switzerland through face-to-face interview. Eligible cases of childhood and adolescent brain tumors (CABT) were ages 7 to 19 years, diagnosed between January 1, 2004 and August 31, 2008, and living in the participating countries (n = 352). The cases were matched by age, sex, and region to 646 population-based controls.

RESULTS

Prenatal exposure to medical diagnostic radiation and postnatal exposure to X-rays were not associated with CABTs. A higher risk estimate of CABTs, although not statistically significant, was found for exposure to head CT scan (OR, 1.86; 95% confidence interval, 0.82-4.22). The associations with head injury, febrile seizure, fever in the first 12 weeks, and general anesthesia were close to unity.

CONCLUSIONS

Prenatal or postnatal medical conditions, including medical diagnostic radiation, were not associated with CABTs. On the basis of small numbers of exposed children, we observed a nonsignificant increased risk for CT scans of the head.

IMPACT

We have presented additional evidence, suggesting that exposure to head CT scan may be associated with the occurrence of CABTs. Cancer Epidemiol Biomarkers Prev; 26(1); 110-5. ©2016 AACR.

Central nervous system (CNS) cancer in children and young people in the European Union and its involvements with socio-economic and environmental factors

Malignant central nervous system (CNS) tumors are the leading cause of death by cancer in children and the second commonest pediatric cancer type. Despite several decades of epidemiologic research, the etiology of childhood CNS tumors is still largely unknown. A few genetic syndromes and therapeutic ionizing radiation are thought to account for 5-10% of childhood cancer, but the etiology of other cases remains unknown. Nongenetic causes, like environmental agents, are thought to explain them. However, as very few epidemiologic studies have been conducted, it is not surprising that nongenetic risk factors have not been detected. The biggest difference between cancers for which there are good etiologic clues and those for which there are none could be the number of relevant studies. This study, which covers the 1980-2011 period, identified links between CNS cancer evolution and the socio-economic and environmental indicators in the same space and time limits in the European Union.

Childhood brain tumor epidemiology: a brain tumor epidemiology consortium review

Childhood brain tumors are the most common pediatric solid tumor and include several histologic subtypes. Although progress has been made in improving survival rates for some subtypes, understanding of risk factors for childhood brain tumors remains limited to a few genetic syndromes and ionizing radiation to the head and neck. In this report, we review descriptive and analytical epidemiology childhood brain tumor studies from the past decade and highlight priority areas for future epidemiology investigations and methodological work that is needed to advance our understanding of childhood brain tumor causes. Specifically, we summarize the results of a review of studies published since 2004 that have analyzed incidence and survival in different international regions and that have examined potential genetic, immune system, developmental and birth characteristics, and environmental risk factors. Cancer Epidemiol Biomarkers Prev; 23(12); 2716-36. ©2014 AACR.

Asthma and risk of brain cancer in children

PURPOSE

Little is known about the causes of central nervous system tumors in children. An inverse association between asthma and brain cancer was found in adults, but there is a dearth of studies in children. The goal of this study was to evaluate the association between asthma and brain cancer in children.

METHODS

Two hundred and seventy-two cases of children with brain tumor diagnosed between 0 and 14 years of age in the Province of Québec, Canada, between 1980 and 1999 and 272 incidence density-matched controls were included in the study. The parents of cases and controls were interviewed by phone using structured questionnaires. Besides asthma in children, family history of asthma, the presence of other atopies, and medication intake were also investigated. Conditional logistic regression was used to analyze the data.

RESULTS

Brain tumor risk was decreased in children with asthma (OR, 0.55; CI 95%, 0.33-0.93), with eczema (OR, 0.52; CI 95%, 0.17-1.57), and with both asthma and eczema (OR, 0.76; CI 95%, 0.18-3.2). Maternal or sibling asthma did not modify the effect of asthma on central nervous system (CNS) tumors, while father's asthma seemed to increase the risk, but numbers were small. Antiasthma medications such as inhaled corticosteroid and beta agonists seemed to increase the risk of CNS tumors (OR for steroids, 2.55; CI 95%, 0.79-8.20 and OR for inhaled beta agonist, 1.62; CI 95%, 0.57-4.63).

CONCLUSIONS

This study strengthens the hypothesis of inverse association between asthma and brain cancer in children, but family history and medications for asthma need further investigation.

Risk of primary childhood brain tumors related to season of birth in Kumamoto Prefecture, Japan

OBJECTIVE

Environmental factors present around the time of birth may induce the development of childhood cancer. Some studies suggested an excess of brain tumors in children born during the winter months. The aim of this study was to look for evidence of the seasonality of birth in children who were younger than 15 years at the time of brain tumor diagnosis in the Kumamoto Prefecture, Japan.

METHODS

We surveyed 115 patients younger than 15 years who were diagnosed with primary intracranial tumors. All patients were born between 1989 and 2003.

RESULTS

We found a statistically significant difference between the season of their birth and the expected distribution of birth dates in the Kumamoto Prefecture (p = 0.028). Among the different diagnostic groups there was a statistically significant winter peak in the birth of patients with germ cell tumor (p = 0.001). No statistically significant seasonal patterns were detected in the birth season of patients with astrocytoma, malignant glioma, and medulloblastoma.

CONCLUSIONS

Although our data provide modest support for a winter peak in the birth of children with brain tumors, we posit that there may be yet unknown, complex biological mechanisms that account for these putative seasonal patterns.

Case control study of periconceptional folic acid intake and nervous system tumors in children

PURPOSE

Since 1992, the Centers for Disease Control and Prevention recommends that women of childbearing age consume 400 µg of folic acid per day to reduce the risk of neural tube defects (NTD). It has been speculated that both NTD and nervous system tumors (NST) may share common mechanisms of altered development. It examines the association between folic acid supplementation and the risk for childhood NST.

METHODS

Incident cases of children with cancer in Spain registered between 2004 and 2006 were identified through the MACAPE Network Group. Tumors were classified as tumors derived from the neuroectoderm (cases) and those with a mesoderm origin (controls). In a second analysis, NST were further divided into central nervous system tumors (CNST) and sympathetic nervous system tumors (SNST). We compared folic acid supplementation between the groups.

RESULTS

Overall, folic acid supplementation any time during pregnancy was similar between cases and controls (odds ratio (OR)=1.05; 95% confidence interval (CI) 0.92-1.20). However, supplementation before the 21st and 36th days of gestation resulted in significantly lower NST than in children with mesoderm tumors (OR=0.34; 95% CI 0.17-0.69 and OR=0.58; 95% CI 0.37-0.91, respectively). Preconceptional intakes of folic acid were also lower in NST although marginally nonsignificant (OR=0.44; 95% CI 0.10-1.02). When NST were divided into CNST and SNST, significant differences between tumors of mesoderm origin were only found for CNST.

CONCLUSIONS

Our results support the hypothesis that folate supplementation reduces the risk of childhood NST, especially CNST. The specific mechanism and cellular role that folate may play in the development of CNST have yet to be elucidated.

The Epidemiology of Childhood Leukemia with a Focus on Birth Weight and Diet

Leukemia is the most common childhood cancer and a major source of morbidity and mortality. The etiology of childhood leukemia remains largely unknown. Cytogenetic abnormalities determine disease subtypes, prognosis, clinical presentation, and course and may help in discovering etiological factors. Epidemiologic investigations of leukemia are complicated by many factors, including the rarity of the disease, necessitating careful study design. Two emerging areas of interest in leukemia etiology are birth weight and diet. High birth weight has been associated with increased risk of childhood leukemia. The biological mechanism behind this association may involve insulin-like growth factor I (IGF-I), which is associated with high birth weight. IGF-I may act by increasing the absolute number of stem cells available for transformation, stimulating the growth of cells that are already transformed, or a combination of effects. Diet has been linked with leukemia. Maternal dietary DNA topoisomerase II (DNAt2) inhibitor intake is associated with infant acute myeloid leukemia (AML) with the MLL gene translocation. Increased intake of fruits and vegetables has been associated with decreased leukemia risk and, relatedly, lack of maternal folate supplementation has been associated with increased childhood leukemia risk, possibly by causing DNA hypomethylation and increased DNA strand breaks. Methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms modify this risk.

Maternal medication use and the risk of brain tumors in the offspring: the SEARCH international case-control study

N-nitroso compounds (NOC) have been associated with carcinogenesis in a wide range of species, including humans. There is strong experimental data showing that nitrosamides (R(1)NNO.COR(2)), a type of NOC, are potent neuro-carcinogens when administered transplacentally. Some medications are a concentrated source of amides or amines, which in the presence of nitrites under normal acidic conditions of the stomach can form NOC. Therefore, these compounds, when ingested by women during pregnancy, may be important risk factors for tumors of the central nervous system in the offspring. The aim of the present study was to test the association between maternal use of medications that contain nitrosatable amines or amides and risk of primary childhood brain tumors (CBT). A case-control study was conducted, which included 1,218 cases and 2,223 population controls, recruited from 9 centers across North America, Europe and Australia. Analysis was conducted for all participants combined, by tumor type (astroglial, primitive neuroectodermal tumors and other glioma), and by age at diagnosis (< or =5 years; >5 years). There were no significant associations between maternal intake of medication containing nitrosatable amines or amides and CBT, for all participants combined and after stratification by age at diagnosis and histological subtype. This is the largest case-control study of CBT and maternal medications to date. Our data provide little support for an association between maternal use of medications that may form NOC and subsequent development of CBT in the offspring.

Maternal diet and infant leukemia: the DNA topoisomerase II inhibitor hypothesis: a report from the children's oncology group

BACKGROUND

The MLL 11q23 translocation arises in utero and is present in 75% of infant leukemias. That MLL+ acute myeloid leukemia (AML) can arise following chemotherapy with DNA topoisomerase II (DNAt2) inhibitors suggests that these substances, which also occur naturally in foods, may contribute toward infant leukemia. We hypothesized that maternal consumption of dietary DNAt2 inhibitors during pregnancy would increase the risk of infant leukemia, particularly AML(MLL+).

METHODS

This Children's Oncology Group case-control study consisted of 240 incident cases of infant acute leukemia [AML and acute lymphoblastic leukemia (ALL)] diagnosed during 1996 to 2002 and 255 random digit dialed controls. Maternal diet during pregnancy was determined through a food frequency questionnaire. An index of specific foods identified a priori to contain DNAt2 inhibitors as well as vegetables and fruits were created and analyzed using unconditional logistic regression.

RESULTS

There was little evidence of an association between the specific DNAt2 index and leukemia overall and by subtype. An exception was AML(MLL+); odds ratios (95% confidence intervals) comparing the second to fourth quartiles to the first were 1.9 (0.5-7.0), 2.1 (0.6-7.7), and 3.2 (0.9-11.9), respectively (P for trend = 0.10). For the vegetable and fruit index, there were significant or near-significant inverse linear trends for all leukemias combined, ALL(MLL+), and AML(MLL-).

CONCLUSION

Overall, maternal consumption of fresh vegetables and fruits during pregnancy was associated with a decreased risk of infant leukemia, particularly MLL+. However, for AML(MLL+) cases, maternal consumption of specific DNAt2 inhibitors seemed to increase risk. Although based on small numbers, these data provide some support for distinct etiologic pathways in infant leukemia.

Maternal smoking during pregnancy and risk of brain tumors in the offspring. A prospective study of 1.4 million Swedish births

OBJECTIVE

Studies of the effect of maternal smoking during pregnancy on development of brain tumors in the offspring generally have found no increase in risk but most have mainly relied on retrospective exposure assessment. We conducted a prospective study on a large birth cohort in Sweden.

METHODS

Women giving birth during 1983-1997 were classified as smokers or non-smokers based on information ascertained at the first prenatal visit and recorded in the Swedish Birth Register. Follow-up of brain tumor incidence among offspring through 1997 was achieved by linkage with the Swedish Cancer Register. Hazard ratios were estimated using Cox proportional hazard regression, adjusting for demographic characteristics available in the Birth Register.

RESULTS

Brain tumors (n=480) occurred at a rate of 4.5 cases per 100,000 person-years. Children of women who smoked during pregnancy had an increased incidence of brain tumors (hazard ratio = 1.24; 95% confidence interval: 1.01-1.53). The increase in risk was similar for benign and malignant tumors, and was most apparent for astrocytoma. The effect of smoking on the occurrence of brain tumors was seen most strongly among 2-4 year-old children.

CONCLUSIONS

These results support a role for maternal smoking during pregnancy in the etiology of childhood brain tumors. Our findings should be confirmed in other prospective studies.

Epidemiology of brain tumors in childhood--a review

Malignant brain tumors are the leading cause of cancer death among children and the second most common type of pediatric cancer. Despite several decades of epidemiologic investigation, the etiology of childhood brain tumors (CBT) is still largely unknown. A few genetic syndromes and ionizing radiation are established risk factors. Many environmental exposures and infectious agents have been suspected of playing a role in the development of CBT. This review, based on a search of the medical literature through August 2003, summarizes the epidemiologic evidence to date. The types of exposures discussed include ionizing radiation, N-nitroso compounds (NOC), pesticides, tobacco smoke, electromagnetic frequencies (EMF), infectious agents, medications, and parental occupational exposures. We have chosen to focus on perinatal exposures and review some of the recent evidence indicating that such exposures may play a significant role in the causation of CBT. The scientific community is rapidly learning more about the molecular mechanisms by which carcinogenesis occurs and how the brain develops. We believe that advances in genetic and molecular biologic technology, including improved histologic subtyping of tumors, will be of huge importance in the future of epidemiologic research and will lead to a more comprehensive understanding of CBT etiology. We discuss some of the early findings using these technologies.

Medulloblastoma and Birth Date: Evaluation of 3 U.S. Datasets

Studies from Norway and Japan have found a higher incidence of medulloblastoma related to births that occur in the fall. The authors sought further evidence concerning this association. For 122 patients in a Duke University database and 90 patients from the Central Cancer Registry of North Carolina, the frequency distribution of birth dates by month was statistically significantly different from the expected North Carolina distribution (p = 0.04 and 0.06). For 75 patients from California Surveillance, Epidemiology, and End Results (SEER) data, the frequency distribution of birth dates by month was marginally different from the expected U.S. distribution (p = 0.14). For 922 patients from national SEER data, the frequency distribution of birth dates by month was not statistically significantly different from the expected U.S. distribution (p = 0.54). Subgroup analysis suggests seasonality of birth dates is most significant for patients aged 5-14 yr diagnosed with medulloblastoma.