Retinoblastoma epidemiology: Does the evidence matter?

It has been proposed that retinoblastoma is ‘caused’ by two sequential mutations affectingthe RB1 gene, but this is a rather outdated view of cancer aetiology that does not take intoaccount a large amount of new acquisitions such as chromosomal and epigenetic alterations.Retinoblastoma remains probably the only cancer in which the rather simplistic ‘two hit’mutational model is still considered of value, although cancer is known to be associatedwith genomic and microsatellite instability, defects of the DNA mismatch repair system,alterations of DNA methylation and hystone acethylation/deacethylation, and aneuploidy.Moreover, as it is shown herein, the predictions made by the ‘two hit’ model, are not fulfilledby the clinical and epidemiological data reported so far. Moreover, while the role ofmutational events in cancer has been largely questioned in the more recent literature,no serious effort has been done to investigate the role of epigenetic alterations and aneuploidyin retinoblastoma.Through the analysis of the specialised literature and a set of original epidemiologicaland biological data concerning retinoblastoma, the authors illustrate the evidences arguingagainst the ‘two hit’ hypothesis and propose that epigenetic factors and aneuploidy playcentral roles in the disease.