The clonogenic cell survival assay has been also applied to a number of non-tumor cellular models, notably lymphoblasts and fibroblasts [26,27,71]; in 1975, Taylor et al. pointed out, for the first time with the clonogenic cell survival assay, the extreme radiosensitivity associated with ataxia telangiectasia (ATM mutations) [45]. This evidence concerns the gene ATM and Ataxia-telangiectasia.