Most inherited cases of breast cancer are associated with one of two abnormal genes: BRCA1 (BReast CAncer gene one) or BRCA2 (BReast CAncer gene two).
Everyone has BRCA1 and BRCA2 genes. The function of the BRCA genes is to repair cell damage and keep breast cells growing normally. But when these genes contain abnormalities or mutations that are passed from generation to generation, the genes don't function normally and breast cancer risk increases. Abnormal BRCA1 and BRCA2 genes may account for up to 10% of all breast cancers, or 1 out of every 10 cases.
Women with an abnormal BRCA1 or BRCA2 gene:
- have about a 69% to 72% lifetime risk of developing breast cancer
- have a much higher-than-average lifetime risk of ovarian cancer; estimates range from 17% to 44%
Breast cancers associated with an abnormal BRCA1 or BRCA2 gene tend to develop in younger women and occur more often in both breasts than cancers in women without these abnormal genes.
A study suggests that just as many women age 50 or younger with an abnormal BRCA1 gene who develop breast cancer are alive 10 years after diagnosis as younger women without an abnormal BRCA1 gene who develop breast cancer.
The study was published online on Aug. 12, 2013 by the Journal of Clinical Oncology. Read the abstract of “Ten-Year Survival in Patients With BRCA1-Negative and BRCA1-Positive Breast Cancer.”
About 2% of all people with breast cancer have an abnormal BRCA1 gene. But the percentage of women with an abnormal BRCA1 gene is higher in women diagnosed at a young age and women diagnosed with triple-negative breast cancer.
Triple-negative breast cancer is cancer that is estrogen-receptor-negative, progesterone-receptor-negative, and HER2-negative.
Because breast cancer is likely to be diagnosed at a younger age, as well as be more aggressive, in women with an abnormal BRCA1 gene, researchers wanted to know there were survival differences between women who did and didn’t have the abnormal gene.
In this Polish study, 3,345 women age 50 or younger who were diagnosed with stage I to stage III breast cancer from 1996 to 2006 were tested for an abnormal BRCA1 gene. In Poland, genetic testing for an abnormal BRCA1 gene has been offered to women newly diagnosed with breast cancer at 17 clinics since 1996.
Of the 3,345 women, 233 (7%) had an abnormal BRCA1 gene. Compared to women without an abnormal BRCA1 gene, women who had the abnormal gene were:
- diagnosed at a younger age (42 versus 44)
- less likely to be diagnosed with estrogen-receptor-positive, progesterone-receptor-positive, or HER2-positive disease
- more likely to be diagnosed with triple-negative breast cancer (69.2% versus 12.9%)
- less likely to have cancer in the lymph nodes; doctors call this having positive lymph nodes (42.5% versus 49.7%)
About 50% of the women with an abnormal BRCA1 gene had had their ovaries removed compared to 14% of the women without an abnormal BRCA1 gene. Of the 395 women who had their ovaries removed, 34 had the surgery before being diagnosed with breast cancer and 361 had the surgery after diagnosis.
Ten years after diagnosis, 80.9% of the women with an abnormal BRCA1 gene were alive compared to 82.2% of women without an abnormal BRCA1 gene.
When the researchers looked at just the women with an abnormal BRCA1 gene, they found that women with positive lymph nodes were 4 times less likely to be alive 10 years after diagnosis than women with negative lymph nodes. Still, women who had their ovaries removed reduced this risk by about 70%.
If you know you have an abnormal BRCA1 gene, the results of this study are reassuring. Overall, women with an abnormal BRCA1 gene had the same 10-year survival rates after being diagnosed with breast cancer as women without an abnormal BRCA1 gene. The study also suggests that women with an abnormal BRCA1 gene need to carefully consider having their ovaries removed preventively -- doing this improved survival by about 70%.
Still, it’s important to consider both the strengths and weaknesses of this study.
- Size of the study: more than 3,300 women participated; the more people that are in a study, the more likely it is that the results can be applied to a wider audience.
- 15% of all women diagnosed with breast cancer in Poland were in the study during the time period; again, this means that the results are more likely applicable to a wider audience.
- The study included women only from Poland; it’s not clear if the results can be applied to women who don’t live in Poland.
- The study wasn’t randomized; this means that the women weren’t randomly assigned to have their ovaries removed. It’s unclear how big a role this played in the women’s survival.
If you or a relative have an abnormal breast cancer gene, it’s important that you work closely with your doctor to get the testing and regular screening that’s best for you.
The American Cancer Society recommends that women with an abnormal breast cancer gene start breast cancer screening at age 30 (compared to age 40 for women with an average risk of breast cancer) or at an earlier age if you and your doctor think that’s best for your situation.
You can learn more about abnormal BRCA1 and BRCA2 genes on the Breastcancer.org Breast Cancer Risk Factors: Genetics page.
Editor’s Note: This article was updated on Jan. 22, 2019, with updated information on cancer risks associated with BRCA mutations.