Leukaemia is the most common cancer type in children worldwide, but childhood leukaemia is a rare disease compared with adult cancers. The most frequent histological subtype is acute lymphoblastic leukaemia (75%), followed by acute myeloid leukaemia (19%). The etiology of childhood leukaemia remains largely unknown, mainly because of its biological diversity and the multifactorial etiology, which involves interactions between genetic and environmental factors. This complexity is further compounded when considering leukaemia subtypes and specific cytogenetic groups characterized by chromosomal changes (i.e. translocation, deletion, and hyperdiploidy).
To overcome the limitations of single epidemiological studies, the Childhood Cancer and Leukemia International Consortium (CLIC) was established in 2007. CLIC builds on a wealth of data and biospecimens collected from more than 25 case–control studies worldwide. In 2017, CLIC expanded to include other paediatric cancers to form CLIC+, which currently focuses on childhood brain tumours and non-central nervous system embryonal tumours. The unprecedented number of children whose data are available for pooling will enhance the statistical power of analyses to investigate the contribution of prenatal and postnatal exposures to the etiology of childhood cancer and its rarer subtypes, and will facilitate the investigation of gene–environment interactions.
CLIC and CLIC+ 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.