The association between sex and most childhood cancers is not mediated by birthweight

A developmental framework for understanding the influence of sex and gender on health: Pediatric pain as an exemplar

Sex differences are a robust finding in many areas of adult health, including cardiovascular disease, psychiatric disorders, and chronic pain. However, many sex differences are not consistently observed until after the onset of puberty. This has led to the hypothesis that hormones are primary contributors to sex differences in health outcomes, largely ignoring the relative contributions of early developmental influences, emerging psychosocial factors, gender, and the interaction between these variables. In this paper, we argue that a comprehensive understanding of sex and gender contributions to health outcomes should start as early as conception and take an iterative biopsychosocial-developmental perspective that considers intersecting social positions. We present a conceptual framework, informed by a review of the literature in basic, clinical, and social science that captures how critical developmental stages for both sex and gender can affect children's health and longer-term outcomes. The literature on pediatric chronic pain is used as a worked example of how the framework can be applied to understanding different chronic conditions.

The association between sex and neonatal respiratory distress syndrome

BACKGROUND

To investigate the association between sex and neonatal respiratory distress syndrome (NRDS).

METHODS

Neonates born at our hospital and transferred to the neonatal department within 1 h were retrospectively analyzed. Depending on whether they developed NRDS during their hospital stay, the neonates was divided into NRDS and non-NRDS groups. There were 142 neonates in the NRDS group (95 males and 47 females) and 310 neonates in the non-NRDS group (180 males and 140 females). The neonates' data on gestational age (GA), sex, birth weight, white blood cell count (WBC), platelet count (PLT), C-reactive protein (CRP), total immunoglobulin M (total IgM), gestational diabetes mellitus(GDM), antenatal steroids use, meconium-stained amniotic fluid, and preterm premature rupture of membranes(PPROM) were gathered.

RESULTS

452 neonates (265 males and 187 females) were involved for the purpose of collecting basic characteristic. Multivariate analysis, males had a 1.87 times higher risk of NRDS than females (P < 0.05) after controlling for the confounding effects of GA, birth weight, WBC, PLT, CRP, total IgM, GDM, antenatal steroids use, meconium-stained amniotic fluid, and PPROM.

CONCLUSIONS

Sex was associated with NRDS; males had a considerably higher risk of NRDS than females.

Gender Differences in Soft Tissue and Bone Sarcoma: A Narrative Review

Sarcomas, uncommon malignancies, stem from mesenchymal tissues, distinct from epithelial tissues, originating in the embryonic mesodermal layer. These sarcomas have been categorized as either bone or soft tissue sarcomas, depending on their originating tissue. The majority of sarcomas occur sporadically with their etiology being unknown, but there are several, well-established genetic predisposition syndromes and some environmental exposures associated with specific sarcomas. Recently, many studies have shown that sarcomas, in analogy with colorectal, skin, head and neck, esophageal, lung, and liver carcinomas, also have a male sex predilection. Significant gender differences have already been observed in childhood sarcomas. Among the tumors strongly associated with the male sex, childhood sarcomas have been identified as being particularly sensitive to the biological differences between the sexes, with special regard to soft tissue sarcomas. As the biological mechanisms underlying the sex differences in the incidence of soft tissue sarcomas remain largely unexplored, this review aims to highlight the factors underlying these differences to inform prevention and treatment.

Paediatric cancer burden in Namibia: A 10-year retrospective, analytical cohort study of patients admitted at Windhoek Central Hospital

BACKGROUND

Childhood cancers are known to cause significant morbidity and mortality, and the incidence has been increasing exponentially in developing countries. Two studies performed in Namibia in 1988 and 2010 have shown changes in the pattern of paediatric cancers over the years. There is a constant need to have updated statistics on the changing trends in the frequency of different types of cancers to inform policy hence the reason for the current study.

METHODS

An analytical retrospective cohort study was performed to analyse paediatric oncology cases that were admitted to the paediatric oncology unit (ward 8 west) at Windhoek Central Hospital (WCH) between 01 January 2011 and 31 December 2020. The study analysed the files of paediatric patients admitted with a paediatric cancer diagnosis from the age of 0 to 16 years. The research data was collected between July 2021 and September 2022.

RESULTS

A total of 174 paediatric cancer patient files met the inclusion criteria. Haematopoietic cancers were the most commonly occurring diagnosis of a paediatric cancer type in the study population (44.8%), of which leukaemias were the most common type of haematopoietic cancer. The other types of cancer apart from haematopoietic cancers consisted of embryonal cancers (37.9%), soft tissue and bone sarcomas (13.8%), and brain or CNS cancers (3.4%). The median age at diagnosis was 5.13 years, with an age range of 0 to 15 years. Fifty five point seven percent (55.7%) were males and 44.3% were females, with a male: female ratio of 1.26:1. Overall, most of the cancers were positively correlated with age, with the interactive-forward test indicating that the method of diagnosis and time significantly (P < 0.05) affected identification at the hospital.

CONCLUSIONS

Haematopoietic cancers remain most common type in Namibia. However, there has been a change in the ranking of the other childhood cancer subtypes over the last 3 decades. Good access to diagnosis and treatment modalities was noted as key to detection and clinical outcomes in the last 10 years (2011 to 2020). For future follow-up studies, prospective studies are recommended.

A protective maternal nutrient concomitant intake associated with acute leukemia might be modified by sex, in children under 2 years

Introduction

Maternal dietary consumption during pregnancy has been inconclusively associated with acute leukemia (AL) in infants, probably because epidemiological evidence has emerged mainly from the analysis of one-by-one nutrient, which is not a real-life scenario. Our objective was to evaluate the association between AL in Mexican children under 2 years of age and their mothers' nutrients concomitant intake during pregnancy, as well as to explore whether there are differences between girls and boys.

Methods

We conducted a study of 110 cases of AL and 252 hospital-based controls in the Mexico City Metropolitan area from 2010 to 2019. We obtained information on maternal intake of 32 nutrients by a food frequency questionnaire and used weighted quantile sum regression to identify nutrient concomitant intakes.

Results

We found a concomitant intake of nutrients negatively associated with AL (OR 0.17; CI95% 0.03,0.88) only among girls; and we did not find a nutrient concomitant intake positively associated with AL.

Discussion

This is the first study that suggests nutrients that have been individually associated with AL are not necessarily the same in the presence of other nutrients (concomitant intake); as well as that maternal diet might reduce AL risk only in girls.

Incidence and Mortality Rates for Childhood Acute Lymphoblastic Leukemia in Puerto Rican Hispanics, 2012-2016

BACKGROUND

Acute lymphoblastic leukemia (ALL) accounts for 80% of all leukemias diagnosed in children. Although ALL age patterns are consistent across racial/ethnic groups, their incidence and mortality rates are highly variable. We assessed the age-standardized ALL incidence and mortality rates of Puerto Rican Hispanic (PRH) children and compared them with those of US mainland Hispanics (USH), non-Hispanic Whites (NHW), non-Hispanic Blacks (NHB), and Non-Hispanic Asian or Pacific Islanders (NHAPI).

METHODS

Differences between racial/ethnic groups were assessed by estimating the standardized rate ratio (SRR) for 2010 to 2014. Secondary data analyses of the Puerto Rico Central Cancer Registry and the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) databases were performed for the 2001 to 2016 period.

RESULTS

PRH children had 31% lower incidence rates than USH, but 86% higher incidence rates than NHB. In addition, the incidence trends of ALL increased significantly from 2001 to 2016 among PRH and USH, with 5% and 0.9% per year, respectively. Moreover, PRH have a lower 5-year overall survival (81.7%) when compared with other racial/ethnic groups.

CONCLUSIONS

PRH children were found to have disparities in ALL incidence and mortality rates compared with other racial/ethnic groups in the US. Additional research is warranted to identify the genetic and environmental risk factors that may be associated with the disparities observed.

IMPACT

This is the first study reporting the incidence and mortality rates of childhood ALL for PRH and making comparisons with other racial/ethnic groups in the US. See related commentary by Mejía-Aranguré and Núñez-Enríquez, p. 999.

Maternal and Paternal Household Pesticide Exposure During Pregnancy and Risk of Childhood Acute Lymphoblastic Leukemia

OBJECTIVE

The aim of this study was to investigate whether risk estimates for childhood acute lymphoblastic leukemia change when restricting model comparison groups to "nonpesticide exposure" (NPE10) households.

METHODS

Cases ( n = 1810) 15 years or younger were identified through Children's Cancer Group institutions between 1989 and 1993 and age-/sex-matched to controls ( n = 1951). Household pesticide use during pregnancy/month prior was collected via telephone. NPE10 comparison group reporting no parental exposure to 10 pesticide classes was identified.

RESULTS

Adjusted odds ratios increased from 15% to 49% when limiting the comparison to NPE10. Maternal termite insecticide exposure was associated with greatest risk (adjusted odds ratio, 4.21; 95% confidence interval, 2.00-8.88). There was minimal evidence of interaction by child sex or occupational pesticide exposure, and no monotonic dose-response pattern with frequency of use (times per year).

CONCLUSIONS

Elevated risks are consistent with published pooled-/meta-analyses and DNA damage. The consistency and magnitude of these associations warrant product labeling, exposure reduction interventions, or both.

Loss of Nf1 and Ink4a/Arf Are Associated with Sex-Dependent Growth Differences in a Mouse Model of Embryonal Rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is an aggressive form of cancer that accounts for half of all pediatric soft tissue sarcomas. Little progress has been made in improving survival outcomes over the past three decades. Mouse models of rhabdomyosarcoma are a critical component of translational research aimed at understanding tumor biology and developing new, improved therapies. Though several models exist, many common mutations found in human rhabdomyosarcoma tumors remain unmodeled and understudied. This study describes a new model of embryonal rhabdomyosarcoma driven by the loss of Nf1 and Ink4a/Arf, two mutations commonly found in patient tumors. We find that this new model is histologically similar to other previously-published rhabdomyosarcoma models, although it substantially differs in the time required for tumor onset and in tumor growth kinetics. We also observe unique sex-dependent phenotypes in both primary and newly-developed orthotopic syngeneic allograft tumors that are not present in previous models. Using in vitro and in vivo studies, we examined the response to vincristine, a component of the standard-of-care chemotherapy for RMS. The findings from this study provide valuable insight into a new mouse model of rhabdomyosarcoma that addresses an ongoing need for patient-relevant animal models to further translational research.

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.

Rhabdomyosarcoma of the oral cavity in children aged 0-2 years: A scoping review

BACKGROUND

The aim of this study was to collect, synthesize, and analyze the clinic-demographic data of rhabdomyosarcoma affecting the oral cavity of young children.

METHODS

The clinical question was "What are the clinical characteristics of oral rhabdomyosarcoma in children aged zero to two years?" Two independent reviewers selected the studies, extracted data, and assessed the methodological quality through the Joanna Briggs Institute Checklist. Descriptive statistics were performed in SPSS. (protocol: osf.io/b9hvy).

RESULTS

Thirty case reports with 41 patients were included (22 males; mean age at diagnosis: 15 months). All studies had some methodological limitations, mainly due to the lack of clarity for a final judgment. More than 70% of the cases affected the tongue or lips. Tumors had a fast growth (mean 2.5 months), usually with red coloration, and variable shape and consistency. Embryonal (63.41%) and alveolar (29.27%) were the most common histological subtypes. Treatment was quite variable but usually included surgery. Most patients (53.66%) were alive without disease at follow-up.

CONCLUSION

Oral rhabdomyosarcoma is rare in children aged 0-2 years without a marked gender predilection. The tumor presents as a fast and infiltrative growth leading to local and/or systemic symptoms, and a favorable prognosis for most patients.

Sex differences in methylation profiles are apparent in medulloblastoma, particularly among SHH tumors

Background

Medulloblastoma, the most common malignant pediatric brain tumor, displays marked sex differences in prevalence of the four main molecular subgroups: SHH, WNT, Group 3 and Group 4. Males are more frequently diagnosed with SHH, Group 3 and 4 tumors, which have worse prognoses than WNT tumors. Little is known about sex differences in methylation profiles within subgroups.

Methods

Using publicly available methylation data (Illumina HumanMethylation450K array), we compared beta values for males versus females. Differentially methylated positions (DMP) by sex within medulloblastoma subgroups were identified on the autosomes. DMPs were mapped to genes and Reactome pathway analysis was run by subgroup. Kaplan-Meier survival curves (Log-Rank p-values) were assessed for each sex within subgroup. MethylCIBERSORT was used to investigate the tumor microenvironment using deconvolution to estimate the abundances of immune cell types using DNA methylation data.

Results

There were statistically significant differences in sex by medulloblastoma subgroups (chi-squared p-value=0.00004): Group 3 (n=144; 65% male), Group 4 (n=326; 67% male), SHH (n=223; 57% male) and WNT (n=70; 41% male). Females had worse survival than males for SHH (p-value=0.02). DMPs by sex were identified within subgroups: SHH (n=131), Group 4 (n=29), Group 3 (n=19), and WNT (n=16) and validated in an independent dataset. Unsupervised hierarchical clustering showed that sex-DMPs in SHH did not correlate with other tumor attributes. Ten genes with sex DMPs (RFTN1, C1orf103, FKBP1B, COL25A1, NPDC1, B3GNT1, FOXN3, RNASEH2C, TLE1, and PHF17) were shared across subgroups. Significant pathways (p<0.05) associated with DMPs were identified for SHH (n=22) and Group 4 (n=4) and included signaling pathways for RET proto-oncogene, advanced glycosylation end product receptor, regulation of KIT, neurotrophic receptors, NOTCH, and TGF-β. In SHH, we identified DMPs in four genes (CDK6, COL25A1, MMP16, PRIM2) that encode proteins which are the target of therapies in clinical trials for other cancers. There were few sex differences in immune cell composition within tumor subgroups.

Conclusion

There are sexually dimorphic methylation profiles for SHH medulloblastoma where survival differences were observed. Sex-specific therapies in medulloblastoma may impact outcomes.

Sex differences in associations between birth characteristics and childhood cancers: a five-state registry-linkage study

BACKGROUND

There is a well-recognized male excess in childhood cancer incidence; however, it is unclear whether there is etiologic heterogeneity by sex when defined by epidemiologic risk factors.

METHODS

Using a 5-state registry-linkage study (cases n = 16,411; controls n = 69,816), we estimated sex-stratified odds ratios (OR) and 95% confidence intervals (95% CI) between birth and demographic characteristics for 16 pediatric cancers. Evidence of statistical interaction (p-interaction < 0.01) by sex was evaluated for each characteristic in each cancer.

RESULTS

Males comprised > 50% of cases for all cancers, except Wilms tumor (49.6%). Sex interacted with a number of risk factors (all p-interaction < 0.01) including gestational age for ALL (female, 40 vs. 37-39 weeks OR: 0.84, 95% CI 0.73-0.97) and ependymoma (female, 40 vs. 37-39 OR: 1.78, 95% CI 1.14-2.79; female, ≥ 41 OR: 2.01. 95% CI 1.29-3.14), birth order for AML (female,  ≥ 3rd vs. 1st OR: 1.39, 95% CI 1.01-1.92), maternal education for Hodgkin lymphoma (male, any college vs. < high school[HS] OR: 1.47, 95% CI 1.03-2.09) and Wilms tumor (female, any college vs. HS OR: 0.74, 95% CI 0.59-0.93), maternal race/ethnicity for neuroblastoma (male, black vs. white OR: 2.21, 95% CI 1.21-4.03; male, Hispanic vs. white OR: 1.86, 95% CI 1.26-2.75; female, Asian/Pacific Islander vs. white OR: 0.28, 95% CI 0.12-0.69), and paternal age (years) for hepatoblastoma in males (< 24 vs. 25-29 OR: 2.17, 95% CI 1.13-4.19; ≥ 35 vs. 25-29 OR: 2.44, 95% CI 1.28-4.64).

CONCLUSIONS

These findings suggest etiologic heterogeneity by sex for childhood cancers for gestational age, maternal education, and race/ethnicity and paternal age.

Trends in pediatric lymphoma incidence by global region, age and sex from 1988-2012

BACKGROUND

Global variation in lymphoma incidence by type and age at diagnosis, region, sex, and Human Development Index (HDI) categories has not been reported, may shed light on potential biologic mechanisms and identify areas for targeted interventions.

METHODS

Using the Cancer Incidence in Five Continents data from 1988 to 2012, we identified Hodgkin (HL), non-Hodgkin (NHL), and Burkitt lymphoma (BL) diagnosed in children aged 0-19 years. We estimated incidence rates (IRs; cases/million) and average annual percent change in incidence (AAPC; 95 % CI) by geographic region, sex, and HDI for each age group (0-9years and 10-19 years).

RESULTS

There were 42,440 NHL, 38,683 H L, and 7703 included. Southern European (SE) 10-19-year-olds (yo) had the highest IR of NHL (19.6 cases/million) in 2008-2012. HL IRs for 0-9yo were <6 cases/million and >25 cases/million for 10-19yo in European regions and Oceania (OC). BL IRs were generally <5cases/million. Northern Europe (NE), SE, and OC 10-19yo had significantly increased APPCs in incidence for all lymphomas with the largest increases in BL (NE AAPC: 7.69 %; 95 % CI: 5.27, 10.16; SE AAPC: 5.21 %; 95 % CI: 3.26, 7.19; OC AAPC: 3.97 %; 95 % CI: 3.26, 4.70). BL incidence increased among males of all ages by approximately 2 %. NHL and BL incidence increased significantly among 10-19yo in very high HDI countries by approximately 3 %.

CONCLUSIONS

Southern and Northern Europe and Oceania displayed increased incidence of all lymphomas studied from 1988 to 2012. BL incidence significantly increased in 8 of 15 global regions, males, and higher HDI countries over the study period. Mechanisms underlying these increases remain to be elucidated.

Comparative international incidence of Ewing sarcoma 1988 to 2012

Ewing sarcoma (ES) is the second most common primary bone tumor in children and adolescents. There are few known epidemiological or genetic risk factors for ES. Numerous reports describe incidence rates and trends within the United States, but international comparisons are sparse. We used the Cancer Incidence in Five Continents (CI5) data to estimate age standardized incidence rates (ASRs; cases per million) and 95% confidence intervals (95% CIs), male-to-female incidence rate ratios (IRRs; 95% CI), and the average annual percent change in incidence (AAPC; 95% CI) for ES by geographic region for children and adults aged 0 to 49 years. We also estimated the ASR for each country or country subpopulation among the 10- to 19-year-old age range; capturing the peak incidence of ES. In total, 15 874 ES cases ages 0 to 49 were reported in the CI5 series between 1988 and 2012. AAPC estimates varied by age group and geographic region. Most of the statistically significant AAPCs showed an increased incidence over time; the only statistically significant decreases in incidence were observed among 20- to 29-year-olds and 30- to 39-year-olds in Southern Asia at -1.93% and -1.67%. When categorized by predominant ancestry, we observed countries and subpopulations with predominately African, East Asian, and Southeast Asian ancestry had the lowest incidence rates, whereas Pacific Islanders and populations with predominantly European and North African/Middle Eastern ancestry had the highest. An excess incidence in males was observed in most regions. Our results highlight substantial variation in ES incidence across geographic populations, reflecting potential ancestral influence on disease risk.

Pediatric Rhabdomyosarcoma: Epidemiology and Genetic Susceptibility

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma in children, yet little is known about its etiology. Studies that examine either environmental exposures or germline genetic predisposition in RMS have begun to identify factors that contribute to this malignancy. Here, we summarize epidemiological reports of RMS incidence in terms of several factors, including age at diagnosis, biological sex, and geographic location. We then describe findings from association studies, which explore the role of parental exposures, birth and perinatal characteristics, and childhood exposures in RMS. Further, we discuss RMS predisposition syndromes and large-scale sequencing studies that have further identified RMS-associated genes. Finally, we propose future directions of study, which aim to advance our understanding of the origin of RMS and can provide knowledge for novel RMS therapies.

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.

Male Sex and the Risk of Childhood Cancer: The Mediating Effect of Birth Defects

Background

There is a persistent, unexplained disparity in sex ratio among childhood cancer cases, whereby males are more likely to develop most cancers. This male predominance is also seen for most birth defects, which are strongly associated with risk of childhood cancer. We conducted mediation analysis to estimate whether the increased risk of cancer among males is partially explained by birth defect status.

Methods

We used a population-based birth cohort with linked data from birth certificates, birth defects registries, and cancer registries from Arkansas, Michigan, North Carolina, and Texas. We conducted counterfactual mediation analysis to estimate the natural direct and indirect effects of sex on cancer risk, modeling birth defect status as mediator. State; birth year; plurality; and maternal race and ethnicity, age, and education were considered confounders. We conducted separate analyses limited to cancers diagnosed younger than 1 year of age.

Results

Our dataset included 10 181 074 children: 15 110 diagnosed with cancer, 539 567 diagnosed with birth defects, and 2124 co-occurring cases. Birth defect status mediated 38% of the association between sex and cancer overall. The proportion mediated varied by cancer type, including acute myeloid leukemia (93%), neuroblastoma (35%), and non-Hodgkin lymphoma (6%). Among children younger than 1 year of age at cancer diagnosis, the proportion mediated was substantially higher (82%).

Conclusions

Our results suggest that birth defects mediate a statistically significant proportion of the relationship between sex and childhood cancer. The proportion mediated varied by cancer type and diagnosis age. These findings improve our understanding of the causal pathway underlying male sex as a risk factor for childhood cancer.

Global trends in incidence rates of childhood liver cancers: A systematic review and meta-analysis

BACKGROUND

Childhood liver cancers are relatively rare, hence inferences on incidence trends over time are limited by lack of precision in most studies.

OBJECTIVE

To conduct a systematic review and meta-analysis of published contemporary trends on childhood liver cancer incidence rates worldwide.

DATA SOURCES

PubMed, EMBASE, CINAHL, Web of Science.

STUDY SELECTION AND DATA EXTRACTION

English-language peer-reviewed articles published from 1 January 2008 to 1 December 2019 that presented quantitative estimates of incidence trends for childhood liver cancer and diagnostic subgroups. Review was conducted per PRISMA guidelines. Two authors independently extracted data and critically assessed studies.

SYNTHESIS

Random effects meta-analysis models were used to estimate pooled incidence trends by diagnostic subgroups. Heterogeneity was measured using the Q and I² statistics and publication bias evaluated using Egger's test.

RESULTS

Eighteen studies were included, all based on population-based cancer registries. Trends were reported on average for 18 years. Overall pooled estimates of the annual percentage change (APC) were 1.4 (95% confidence interval [CI] 0.5, 2.3) for childhood liver cancers, 2.8 (95% CI 1.8, 3.8) for hepatoblastoma and -3.0 (95% CI -11.0, 4.9) for hepatocellular carcinoma. Sub-group analysis by region indicated increasing trends for childhood liver cancers in North America/Europe/Australia (APC 1.7, 95% CI 0.7, 2.8) whereas corresponding trends were stable in Asia (APC 1.4, 95%CI -0.3, 2.7). Publication bias was not detected for any of these analyses. The I² statistic indicated that the heterogeneity among included studies was low for combined liver cancers, moderate for hepatoblastoma and high for hepatocellular carcinoma.

CONCLUSIONS

Incidence is increasing for childhood liver cancers and the most commonly diagnosed subgroup hepatoblastoma. Lack of knowledge of the etiology of childhood liver cancers limited the ability to understand the reasons for observed incidence trends. This review highlighted the need for ongoing monitoring of incidence trends and etiological studies.

Recent advances in understanding and managing pediatric rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is a high-grade malignant neoplasm, with a morphologic appearance mimicking that of developing skeletal muscle. Over the last 30 years, patient outcomes have improved with the incorporation of multimodal therapies, including chemotherapy, radiation therapy, and surgery. The overall cure rates exceed 70%, with patients who have low-, intermediate-, and high-risk disease experiencing long-term survival rates of >90%, 70%, and <30%, respectively. Historically, RMS was classified according to histology; however, recent advances have revealed new molecular subgroups that allow us to more accurately identify high-, intermediate-, and low-risk disease. In this review, we discuss recent advances made in understanding RMS tumor biology and propose how this understanding can drive a new classification system that can guide clinical approaches for treatment de-escalation in patients with expected favorable outcomes and escalation for those with expected poor outcomes.

Survival differences by race/ethnicity among children and adolescents diagnosed with germ cell tumors

Survival differences by racial and ethnic group have been reported in children and adolescents with germ cell tumors (GCTs), but whether these differences depend on stage of disease is unclear. Using the SEER 18 registries (2000-2015), we examined GCT survival differences by race/ethnicity (non-Hispanic white [NHW], Black, Asian/Pacific Islander [API], Hispanic) separately for males and females aged 0-19 years at diagnosis. We used Kaplan-Meier survival curves (Log-Rank p values) to characterize survival differences. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) for the association between race/ethnicity and death. Using an inverse odds weighting mediation analysis, we estimated the association between race/ethnicity and death treating stage of disease as the mediator. There were no significant racial/ethnic survival differences among females. Male survival differed by race/ethnicity (p < 0.0001) with NHW males having the best survival. Compared to NHW, API and Hispanic males had significantly higher risks of death (API HR: 2.18; 95% CI: 1.32-3.56; Hispanic HR: 1.98; 95% CI: 1.42-2.78) (model adjusted for age and year at diagnosis, tumor histology and location, stage). This association was mediated by stage of disease only among Hispanic males with gonadal tumors (indirect HR: 1.18; 95% CI: 1.03-1.35). The increased risk of death after a testicular GCT diagnosis observed among Hispanic males was mediated by stage of disease. For API males and Hispanic males with extragonadal tumors, other unidentified factors including differences in exposures, tumor biology or treatment received may impact the observed racial/ethnic survival disparities.

Sex ratio among childhood cancers by single year of age

BACKGROUND

The male excess in childhood cancer incidence is well-established; however, the underlying biologic mechanisms remain unknown. Examining the association between male sex and childhood cancer by single year of age and tumor type may highlight important periods of risk such as variation in growth and hormonal changes, which will inform etiologic hypotheses.

METHODS

Using data from the Surveillance, Epidemiology, and End Results (SEER) 18 registries (2000-2015), incidence rate ratios (IRR) and 95% confidence intervals (95% CI) were estimated as the measure of association between male sex and childhood cancer by single year of age (0-19).

RESULTS

The IRR for male cancer overall was 1.19 (95% CI, 1.18-1.20) and was similar in magnitude at nearly every year of age. Burkitt lymphoma was strongly associated with male sex (IRRs ≥2 at each year of age). Increased incidence was observed among males for acute lymphoblastic leukemia, Hodgkin and non-Hodgkin lymphomas for nearly all years of age. Medulloblastoma was the only central nervous system tumor with a significant male predominance at nearly every age. Male sex displayed a consistent inverse association with nephroblastoma and thyroid carcinoma over the ages studied.

CONCLUSIONS

Male sex was positively associated with most cancers. The higher incidence rates observed in males remained consistent over the childhood and adolescent periods, suggesting that childhood and adolescent hormonal fluctuations may not be the primary driving factor for the sex disparities in childhood cancer. The observed incidence disparities may be due to sex differences in exposures, genetics, or immune responses.

Survival Differences Between Males and Females Diagnosed With Childhood Cancer

Background

Males have worse survival for childhood cancer, but whether this disparity exists among all childhood cancer types is undescribed.

Methods

We estimated sex differences in survival for 18 cancers among children (0–19 years) in Surveillance, Epidemiology, and End Results 18 (2000–2014). We used Kaplan-Meier survival curves (log-rank P values) to characterize sex differences in survival and Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between sex and death for each cancer type. We used an inverse odds weighting method to determine whether the association between sex and death was mediated by stage of disease for solid tumors.

Results

Males had worse overall survival and a higher risk of death for acute lymphoblastic leukemia (HR = 1.24, 95% CI = 1.12 to 1.37), ependymoma (HR = 1.36, 95% CI = 1.05 to 1.77), neuroblastoma (HR = 1.28, 95% CI = 1.09 to 1.51), osteosarcoma (HR = 1.29, 95% CI = 1.08 to 1.53), thyroid carcinoma (HR = 3.25, 95% CI = 1.45 to 7.33), and malignant melanoma (HR = 1.97, 95% CI = 1.33 to 2.92) (all log-rank P values < .02). The association between sex and death was mediated by stage of disease for neuroblastoma (indirect HR = 1.12, 95% CI = 1.05 to 1.19), thyroid carcinoma (indirect HR = 1.24, 95% CI = 1.03 to 1.48), and malignant melanoma (indirect HR = 1.28, 95% CI = 1.10 to 1.49). For these six tumors, if male survival had been as good as female survival, 21% of male deaths and 13% of total deaths after these cancer diagnoses could have been avoided.

Conclusions

Consideration of molecular tumor and clinical data may help identify mechanisms underlying the male excess in death after childhood cancer for the aforementioned cancers.