To start things off, we’re publishing an overview on genetics and family history in breast cancer from the book “TOGETHER – Every Woman’s Guide to Preventing Breast Cancer.”
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Of all the factors linked to breast cancer, family history is the one most people are likely to put at the top of the list. Yet, while there’s no denying the importance of family history, for most women it’s not as key a factor as they might think.
Having a mother or sister with breast cancer (who are called first-degree relatives) increases the risk of the disease by about 50 percent. If both your mother and sister had breast cancer, or developed it at an early age, it can double or triple risk. While these numbers are nothing to dismiss, they’re not much higher than those of other risk factors for the disease – like obesity or postmenopausal hormone use.
Of course, there are exceptions. For some women who do have a special genetic or family history, risk of breast cancer can be greatly increased. The most well known example of this is women who have mutations in the BRCA1 or 2 genes. These mutations impart an approximately 45 – 65 percent lifetime risk of developing breast cancer. This compares to the 12 percent lifetime risk of the average woman in the United States.
The increased risk linked to BRCA1/2 mutations is striking but doesn’t mean that every woman with a BRCA1/2 mutation will develop breast cancer. Looking at the numbers from the opposite standpoint, 35 – 55 percent of women with these mutations will not go on to develop the disease.
Thankfully, BRCA1/2 mutations are rare. Around one in 300-400 women in the United States has a BRCA1/2 mutation, which translates to just around a quarter of one percent (0.25 percent) of American women.
Other less well known genetic conditions can also greatly increase the risk of breast cancer, such as mutations in the genes TP53, PALB2, CDH1, ATM, CHEK2, PTEN, and others. Outside of known mutations, a significant family history can also signal an important genetic susceptibility to breast cancer. Hereditary Breast and Ovarian Cancer Syndrome is marked most frequently by having multiple family members with cancer, especially at younger ages; a single family member who has had multiple different cancers; and breast cancer in male family members.
For women who have these very high-risk conditions, it’s important to seek advice from a genetic counselor and to talk with a breast cancer specialist about options to manage the risk of the disease. The most common approaches for women with a high-risk mutation or strong family history include: watchful waiting with frequent screening tests that can help find any cancer that does develop in early stages; taking prescription risk-reducing medication; or having preventive surgery that removes the breasts (bilateral prophylactic mastectomy) and maybe also the ovaries (bilateral oophorectomy), which can further lower risk.
Despite some high profile stories in the news touting one option over another, each of these approaches has its merits. Genetic counselors and a woman’s breast health specialist can help her work through all the choices and help her decide which may be the best for her.