Because a high Body Mass Index (BMI), which is an indicator of high body fatness, and the use of chemotherapy, compounded this increased risk in BRCA1/2 carriers, further investigation should clarify if, in addition to cell-autonomous mechanisms, the metabolic facet of BRCA1 one-hit also involves significantly imbalanced non-cell-autonomous environmental factors (e.g., IGF-I, estrogens) compared to women treated for breast cancer who do not have a BRCA mutation [66-68]. This evidence concerns the gene BRCA1 and breast cancer.