Almost 13% of breast cancers are due to a hereditary predisposition associated with high or moderate penetrance of genes. The 2 genes most responsible for breast cancer are the BRCA1 gene on chromosome 17 and the BRCA2 gene on chromosome 13. Mutations in these genes place a high risk of developing breast cancer or ovarian cancer. Gene mutations in the BRCA2 gene are responsible for the increased risk of male breast cancer. Other genes thought to be responsible for a 1.5-7.5 greater risk of developing breast cancer compared to the general population are CHEK2, BRIP1, MSH6, BARD1,ATM, RAD51D and PALB2.
The risk of developing breast and ovarian cancer in 80-year-old women with BRCA1 and BRCA2 mutations are listed in the table below (Kuchenbaecker KB, PEOPLE 2017) (3)
(3) (Kuchenbaecker KB, JAMA 2017)
|MUTATION BRCA1||MUTATION BRCA2|
|BREAST CANCER RISK||72%||69%|
|OVARIAN CANCER RISK||44%||17%|
There are 4 levels of risk for breast or ovarian cancer:
High with no confirmed genetic mutation
High with confirmed genetic mutation
CRITERIA FOR ONCOLOGICAL GENETIC TESTING
Oncological genetic testing is necessary when the woman has at least 1 of the following criteria:
Personal or family history
In case of finding the gene mutation, the genetic test could also be carried out by the other family members from the age of 18 and over. In the case of a mutation of uncertain significance, there is no need for family members to proceed with genetic testing, except for research purposes.