BRCA1 and cancer: A typical example of this statement is to consider the relative risk of leukemia associated with homozygous ATM mutations (which is significantly higher than 10) on one hand, and, on the other, the relative risk of breast cancer associated with heterozygous BRCA1 mutations (between 2 and 10) that provides a very weak radiosensitivity [93]: there is no intermediate relative risk of cancer corresponding to intermediate radiosensitivity (Table 1).