The Childhood Cancer and Leukemia International Consortium (CLIC) was founded in 2006 and established in 2007 with the purpose of building on the wealth of data and biospecimens collected from case–control studies worldwide. CLIC pools information from studies all around the world to answer the big questions in childhood leukaemia research. CLIC is composed of a group of international researchers from studies in 21 countries with 28 principal investigators, representing approximately 30 000 children with leukaemia (cases) and 2 330 000 children without leukaemia (controls).

CLIC has identified – with enhanced precision – associations of childhood leukaemia with multiple chemicals, immune factors, prenatal folic acid/vitamin supplementation, and fetal growth. Analyses have evaluated the effects of these environmental risk factors, alone and in combination with genetic factors, on risk of childhood leukaemia overall and by subtype. CLIC analyses incorporate methodological evaluations of systematic errors inherent to case–control design by comparing interview-based versus registry-based studies, and by conducting quantitative bias analyses. CLIC has a shared governance and transparent procedures for membership, data sharing, scientific review, and authorship. The success of CLIC is evidenced by its publications and ongoing pooled analyses, and also by the training of young investigators in the field of molecular and environmental epidemiology of childhood cancers.

In 2017, CLIC expanded to include other paediatric cancers to form CLIC+, which currently focuses on childhood brain tumours (~14 000 children) and non-central nervous system embryonal tumours (~18 000 children).

The primary goals of CLIC and CLIC+ are to share comparable epidemiological and genetic data to enhance the statistical power of analyses to investigate the contribution of prenatal and postnatal exposures to the risk of childhood cancers. Such factors include pregnancy and birth characteristics, medical conditions, diet and vitamin supplementation, chemical use at home and at work, and measures of immune function and infections.

CLIC and CLIC+ offer a platform to share expertise and ideas among researchers from different disciplines, including epidemiologists, tumour biologists, geneticists, immunologists, clinicians, toxicologists, and statisticians. These consortia also provide a unique opportunity not only to fill gaps in knowledge about disease etiology but also to play an active role in research translation and outreach for the prevention of childhood cancers worldwide.

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