The association between increased chromosomal radiosensitivity and sporadic breast cancer risk has been reported6, and a number of DNA DSB repair genes including BRCA1, BRCA2, ATM, CHEK2, PALB2, TP53, Rad51C, Rad51D, and NBS1 have been identified as being causative of hereditary breast and ovarian cancer (HBOC)10. This evidence concerns the gene ATM and breast cancer.