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Season of birth, a surrogate of seasonal variation of environmental exposures, has been associated with increased risk of several cancers. In the context of a Southern‐Eastern Europe (SEE) consortium, we explored the potential association of birth seasonality with childhood (0–14 years) central nervous system (CNS) tumors. Primary CNS tumor cases (n = 6,014) were retrieved from 16 population‐based SEE registries (1983–2015). Poisson regression and meta‐analyses on birth season were performed in nine countries with available live birth data (n = 4,987). Subanalyses by birth month, age, gender and principal histology were also conducted. Children born during winter were at a slightly increased risk of developing a CNS tumor overall [incidence rate ratio (IRR): 1.06, 95% confidence intervals (CI): 0.99–1.14], and of embryonal histology specifically (IRR: 1.13, 95% CI: 1.01–1.27). The winter peak of embryonal tumors was higher among boys (IRR: 1.24, 95% CI: 1.05–1.46), especially during the first 4 years of life (IRR: 1.33, 95% CI: 1.03–1.71). In contrast, boys <5 years born during summer seemed to be at a lower risk of embryonal tumors (IRR: 0.73, 95% CI: 0.54–0.99). A clustering of astrocytomas was also found among girls (0–14 years) born during spring (IRR: 1.23, 95% CI: 1.03–1.46). Although the present exploratory results are by no means definitive, they provide some indications for age‐, gender‐ and histology‐related seasonal variations of CNS tumors. Expansion of registration and linkage with cytogenetic reports could refine if birth seasonality is causally associated with CNS tumors and shed light into the complex pathophysiology of this lethal disease. What's new? Does the risk of developing childhood central nervous system (CNS) tumors depend on the season of birth? The answer is yes. Age‐, gender‐ and histology‐related seasonal variations of CNS tumors were found, namely a winter birth clustering among boys with embryonal tumors, mostly marked in the course of the first four years of life. The authors recommend an expansion of cancer registration and linkage with cytogenetics that could refine if birth seasonality is a potential indicator of early‐life exposures associated with CNS tumor risk. [ABSTRACT FROM AUTHOR]

Neuroblastoma comprises the most common neoplasm during infancy (first year of life). Our study describes incidence of neuroblastoma in Southern–Eastern Europe (SEE), including – for the first time – the Nationwide Registry for Childhood Hematological Malignancies and Solid Tumors (NARECHEM‐ST)/Greece, compared to the US population, while controlling for human development index (HDI). Age‐adjusted incidence rates (AIR) were calculated for 1,859 childhood (0–14 years) neuroblastoma cases, retrieved from 13 collaborating SEE registries (1990–2016), and were compared to those of SEER/US (N = 3,166; 1990–2012); temporal trends were assessed using Poisson regression and Joinpoint analyses. The overall AIR was significantly lower in SEE (10.1/million) compared to SEER (11.7 per million); the difference was maximum during infancy (43.7 vs. 53.3 per million, respectively), when approximately one‐third of cases were diagnosed. Incidence rates of neuroblastoma at ages <1 and 1–4 years were positively associated with HDI, whereas lower median age at diagnosis was correlated with higher overall AIR. Distribution of primary site and histology was similar in SEE and SEER. Neuroblastoma was slightly more common among males compared to females (male‐to‐female ratio: 1.1), mainly among SEE infants. Incidence trends decreased in infants in Slovenia, Cyprus and SEER and increased in Ukraine and Belarus. The lower incidence in SEE compared to SEER, especially in infants living in low HDI countries possibly indicates a lower level of overdiagnosis in SEE. Hence, increases in incidence rates in infancy noted in some subpopulations should be carefully monitored to avoid the unnecessary costs health impacts of tumors that could potentially spontaneously regress. [ABSTRACT FROM AUTHOR]