Conclusions
The association of environmental factors and childhood cancer risk has
been extensively studied, albeit yielding inconclusive so far results.
Our exhaustive literature search on these factors and risk of 10
different childhood cancer types showed that only half of the reported
associations reached a nominally statistical significance level, while
only 2.4% of published meta-analyses were supported by highly
suggestive evidence. Beyond any limitations and biases that may affect
the summary effect estimates, the present findings, supported by
mechanistic information, provide highly suggestive evidence that
exposure to seven maternal/neonatal factors (including prenatal exposure
to environmental chemicals or intake of B-vitamins) significantly
affects -either increases or decreases- the risk of childhood leukemia,
CNS tumors and testicular cancer. Considerable uncertainty remains for
other stressors and outcomes. Further evidence from sufficiently powered
studies and large consortia with uniform reporting of analyses is needed
to allow firmer conclusions to be drawn. Given the increasing trend in
the westernization of habits, evidence of the strength of the
associations between lifestyle influences and childhood cancer may allow
finer identification of people at high risk, who could be selected for
individual-based primary prevention strategies.
Contributors : MK and EEN conceived and designed the study. MK,
GM, CT, AK, XT and EEN acquired and collected the data. MK and GM
analyzed the data. MK drafted the initial version of the manuscript. GM,
CT, AK, XT, KT, LG, JS, A-BH, TS, AH, EP and EEN drafted and critically
revised the manuscript for important intellectual content and gave final
approval of the version to be published. EEN is the guarantor.
Acknowledgments/Funding: The present study is co-financed by
Greece and the European Union (European Social Fund- ESF) through the
Operational Programme «Human Resources Development, Education and
Lifelong Learning» in the context of the project “Reinforcement of
Postdoctoral Researchers - 2nd Cycle” (MIS-5033021),
implemented by the State Scholarships Foundation (ΙΚΥ). None of the
funders had any influence on the study design; in the collection,
analysis, and interpretation of data; in the writing of the report; and
in the decision to submit the article for publication. All authors had
access to the data in the study and had final responsibility for the
decision to submit for publication. Where authors are identified as
personnel of the International Agency for Research on Cancer/ World
Health Organization, the authors alone are responsible for the views
expressed in this article and they do not necessarily represent the
decisions, policy or views of the International Agency for Research on
Cancer/ World Health Organization.
Competing Financial Interests: All authors have completed the
ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and
declare: no support from any organization for the submitted work; no
financial relationships with any organizations that might have an
interest in the submitted work in the previous three years; no other
relationships or activities that could appear to have influenced the
submitted work.
Ethical approval: Not required.
Data sharing: No additional data available.
Transparency : The lead author (MK) affirms that the manuscript
is an honest, accurate, and transparent account of the study being
reported; that no important aspects of the study have been omitted; and
that any discrepancies from the study as planned have been explained.