Does a BRCA mutation mean I will get cancer?

No. Inheriting a harmful change in the BRCA1 or BRCA2 gene raises the risk of certain cancers, but it does not mean cancer is certain.

The National Cancer Institute is clear that a positive BRCA test result cannot tell whether or when a person will develop cancer. Some people who inherit a harmful BRCA change never develop cancer at all.

The numbers show both halves of that sentence at once. More than 60% of women who inherit a harmful BRCA1 or BRCA2 change will develop breast cancer in their lifetime. In the general population, about 13% of women will. For ovarian cancer the gap is even sharper. About 39% to 58% of women with a harmful BRCA1 change and 13% to 29% with a harmful BRCA2 change will develop it, compared with about 1.1% of women overall.

So the risk is high and it is real. It is also not 100%.

There is a second number people often miss. Some women have already had breast cancer. Among them, roughly 30% to 40% of those with a BRCA1 change and about 25% of those with a BRCA2 change will develop cancer in the other breast within 20 years. In the general population that figure is about 8%.

What a positive result does offer is information. Knowing about a harmful change lets a person and their care team consider earlier or more frequent screening, steps to reduce risk, and, for someone who already has cancer, treatment choices. Because relatives share genes, the information can also matter for blood relatives.

The options that follow are worth knowing in specific terms.

For breast cancer, the recommended screening is MRI along with mammography, not mammography alone. Some women choose surgery to remove both breasts, which lowers risk. NCI notes that risk-reducing surgery does not guarantee that cancer will not develop.

For ovarian cancer, the picture is harder, and honesty matters here. No effective ovarian cancer screening method is known.

Medicines are a partial answer at best. Tamoxifen and raloxifene are used to lower breast cancer risk in some women, but their effectiveness specifically for BRCA carriers is not clear.

A genetic counselor can help explain what a result means for you and your family. Bring your questions in concrete form. Ask: what is my estimated risk by age, which screening should start at what age, what are the tradeoffs of surgery for someone my age, and who else in my family should be tested.