The BRCA Gene: What Women Really Need to Know
BRCA sounds pretty scary, but, in reality, all humans have BRCA1 and BRCA2 (Breast Cancer genes 1 and 2). In fact, when these genes are "normal," they actually help us. They produce tumor suppressor proteins that help repair damaged DNA, thereby playing an important role in ensuring genetic matter in cells remains stable.
The trouble comes when these genes are mutated or altered. When this happens, the protective proteins are either not produced at all or don’t function as they should. As a result, cells are more likely to develop additional genetic alterations, some of which are linked to cancer. Experts estimate between 1 in 300 to 1 in 800 people carry one of these harmful mutations. The prevalence is much higher in some populations, such as Ashkenazi Jews. Both men and women can have mutated or altered BRCA genes, with a 50% likelihood of passing them down to their children.
BRCA Gene Mutations and Cancer Risk
Specific inherited BRCA1 and BRCA2 gene mutations significantly raise the risk of breast and ovarian cancers. About 12% of women will develop breast cancer at some point during their lives, but some sources state 55-65% of women with a harmful BRCA1 mutation and about 45% with a harmful BRCA2 mutation will develop breast cancer by age 70. Other sources list a lifetime incidence of 40-80% for both mutations; by this calculation, those with the harmful gene mutation are 3-6 times more likely to develop breast cancer than those without a gene mutation.
Photo: Breast cancer screening
About 1.3% of women will develop ovarian cancer at some point in their lives, while 39% of women with a harmful BRCA1 mutation and 11-17% with a harmful BRCA2 mutation will develop ovarian cancer by age 70. This means women with a harmful BRCA1 mutation are 30 times more likely to develop ovarian cancer, and women with a harmful BRCA2 mutation are 8-13 times more likely to develop ovarian cancer.
Photo: Ovarian cancer MRI
- BRCA2 is associated with double or triple the risk of melanoma, including a higher than average risk of melanoma of the eye.
- A BRCA1 mutation is associated with double or triple the lifetime risk of developing pancreatic cancer and a triple to quintuple risk in BRCA2 mutation carriers. About 4-7% of people with pancreatic cancer have a BRCA mutation.
- BRCA1 mutations are linked to specific types of leukemia and BRCA2 mutations are linked to some types of lymphoma and leukemia.
- BRCA1 families may have four times the risk of developing colon cancer on the high end, while BRCA2 carriers have double the risk.
Recent BRCA Research
Several studies have shown not all BRCA mutations equate to the same cancer risk. A BRCA1 mutation in which a small glitch caused a protein to have the wrong amino acid was found to increase breast cancer risk from 59% to 69% by age 70. This was also the case for mutations in which the gene skipped some steps in making a protein, and a mutation associated with Jewish heritage. A particular kind of mutation causing the protein to be truncated in BRCA 2 was associated with a relatively low 40% risk of breast cancer by age 70. Researchers concluded these findings may influence risk assessment and cancer prevention decision making in individuals with these mutations.
Who Should Get Genetic Testing for the BRCA Gene?
On May 14, 2013, Angelina Jolie wrote a New York Times editorial in which she eloquently spoke about having a faulty BRCA1 gene and her decision to undergo a prophylactic (preventive) double mastectomy. This greatly increased public awareness of hereditary breast cancer and preventive surgery. Research also showed the editorial was associated with increased genetic testing equating to 4,500 more BRCA tests among commercially insured adult women in the 15-day period following publication. Mastectomy rates actually decreased in women who had genetic testing, from 10% in January-April 2013 to 7% in May-December 2013.
It’s clear the celebrity factor impacts healthcare decisions, but who should undergo BRCA testing? Only people who are deemed at high risk should have this testing. A genetic counselor can help people figure out if their family history suggests an inherited pattern of breast and ovarian cancers. You can do a self-assessment at KnowBRCA.