Previous literature
Our study aimed to address the open question whether childhood cancer is a preventable disease by implementing interventions on candidate risk factors . Our results are in line with those reported by recent studies and support the hypothesis that the origins of childhood cancer seem to be influenced not only by genetics, but also by the perturbation of the normal developmental processes following exposure to exogenous stressors . Currently, no primary preventive measures for childhood cancer have been established. The main reasons include the lack of causative determination on the level of available evidence, the lack of determination of the effectiveness of interventions at population level, as well as our current inability to specify the hazardous conditions in terms of exposure level . Acknowledging the challenges in determining causation and in quantifying the need for preventive measures to be undertaken in the field of environmental health, we aimed to stringently appraise the validity of evidence and potential biases in the context of an umbrella review, namely a critical integration of evidence stemming from currently published systematic reviews and meta-analyses. Our grading of evidence largely conforms to systematic analyses of the literature performed by the World Cancer Research Fund (WCRF) and the International Agency for Research on Cancer (IARC), as well as to the protocols proposed by the US Preventive Services Task Force (USPSTF) .
A strong level of evidence was not supported by the present study primarily due to the presence of biases (i.e. significant between-study heterogeneity). However, beyond these limitations, our results provided highly suggestive evidence for some specific and potentially preventable risk factors of childhood cancer, which supports those reported by recently published studies, systematic reviews and pooled analyses from large consortia .