If you are a woman who has been identified as a bearer of the BRCA1 or BRCA2 gene mutation, it is estimated that you are one of roughly 12 percent of the overall female population that will develop breast cancer at some point. The percentages on those odds differ as to which gene is affected, although even having a healthy one is no guarantee against developing cancer.

If you have a mutated BRCA1, you have as much as a 65 percent chance of developing breast cancer. If you have a BRCA2 mutation, it’s about a 45 percent chance.

Ovarian cancer rates are different for the gene mutations. It’s estimated that just 1.3 percent of women will get ovarian cancer during their lifetimes. But if you have a BRCA1 mutation, you can have as much as a 39 percent chance of developing the disease. Those with a BRCA2 mutation have as much as a 17 percent chance of developing ovarian cancer.

These are estimates based on the genetic research that has been done to date, and it’s cautioned that no long-term studies have been done to differentiate women with cancer from those who develop cancer because of mutated BRCA1 or BRCA2 mutations. It is possible the information could change.

There are other factors that play an important role in determining the odds of a woman developing cancer. A family history that includes ovarian cancer or breast cancer, the type of BRCA1 and BRCA2 mutations that occur, the woman's reproductive history and even the patient's previous medical history all can play a role.

Other Disease Risks

BRCA1 and BRCA2 mutations may cause fallopian tube and peritoneal cancer and pancreatic cancer. Men also can develop breast cancer, and children are susceptible to myeloid leukemia from gene mutations.