For a long time, researchers believed that hereditary breast cancers were caused by defective genes, passed from generation to generation. This belief led them on a long search that came to an end when they announced the discovery of the defective genes known as BRCA1 and BRCA2.
While identification of these genes is a giant step forward in breast cancer research, it’s noteworthy that these genes appear to play no role in the development of the more prevalent, nonhereditary forms of breast cancer. Those forms constitute the majority of breast cancer cases and strike more than 175,000 women in the United States each year.
About 5 percent to 10 percent of all cases of breast cancer are believed to be family-linked, and BRCA1 and BRCA2 could account for about half of those cases. Women who have a BRCA mutation have a 60 percent to 85 percent lifetime risk of developing breast cancer, and many will develop it before age 50. (The lifetime risk for all women is 12.5 percent, or 1 in 8.) In addition, women who carry BRCA1 have a sharply elevated risk of developing ovarian cancer. Scientists estimate that 1 in 300 to 500 women have inherited a BRCA gene. More than 2 percent of all Jewish women of Ashkenazi descent carry BRCA1 or BRCA2 genes, making them much more likely to have a BRCA mutation than women in the general population.
Because BRCA1 and BRCA 2 are associated only with family-linked breast cancers and ovarian cancer, a diagnostic test would be recommended only for women who believe they come from families who are at high risk for these cancers, such as:
- Any woman who has more than one first-degree relative—a sister, mother or daughter—with breast or ovarian cancer. (Or only one first-degree relative for women of Ashkenazi descent.)
- Women with multiple family members who have been stricken with breast cancer before age 50 or with cancer in both breasts at any age.
- Women with a male relative who has breast cancer.
Regular and frequent mammograms, as well as clinical exams by a health professional, are vital to the health of all women. Regular exams are even more crucial for carriers of BRCA1 and BRCA2. These steps can lead to early detection, which is the key to surviving breast cancer. According to the American Cancer Society, all women should practice the following breast-screening guidelines:
- Get a screening mammogram by age 40. Then have a mammogram every year.
- Have your breasts examined by a health professional at least every three years between ages 20 and 40, and every year from age 40 on.
- Report any changes in your breasts to your doctor immediately.
Women who are carriers of BRCA1 and BRCA2 should get an annual magnetic resonance imaging scan along with a mammogram beginning at age 30. The most important thing you can do is stay vigilant.