Angelina Jolie joins a growing number of women who have used genetic testing… (Dan Kitwood / AFP-Getty…)
By opting for surgery to remove her breasts while they were still healthy, Angelina Jolie joined a growing number of women who have used genetic testing to take control of their health.
Here are answers to some common questions about how DNA influences breast cancer risk and what women can do about it.
What genes are involved in breast cancer?
The two primary ones are known as BRCA1 and BRCA2. Hundreds of variants of these genes have been found that make a woman — or a man — more likely to develop breast cancer. The mutations can increase one's lifetime risk of breast cancer from about 50% to more than 85%, said Rebecca Nagy, president of the National Society of Genetic Counselors.
FOR THE RECORD:
DNA and breast cancer: A Q&A in the May 15 Section A about how genes influence breast cancer risk implied that the average woman's risk of developing breast cancer was 50%. As stated elsewhere in the article, most women face a 12% to 13% lifetime risk of the disease. For women who have certain mutations in their BRCA1 and BRCA2 genes, that risk rises to between 50% and 87%.
In her essay in the New York Times, Jolie said her doctors believed the mutation found in her BRCA1 gene raised her chance of developing the disease to 87%.
Scientists know of variants in other genes that also play a role in breast cancer, but these occur more rarely than the BRCA mutations, said Nagy, who works at Ohio State University's James Cancer Hospital in Columbus.
How many people have these mutations?
Everyone has the BRCA1 and BRCA2 genes, but only about 1 in 600 women have variants known to increase the risk of breast cancer, said Ellen Matloff, director of cancer genetic counseling at the Yale Cancer Center in New Haven, Conn.
The variants are more common in certain groups of people, including Jews from Europe, and are also linked to ovarian cancer in women. BRCA2 mutations, additionally, are associated with an increased risk of pancreatic cancer, Matloff said. Other cancers have also been linked to mutations in the two genes.
Should I get tested to see whether I have these mutations?
Not necessarily. At the Yale Cancer Center, genetic counselors only recommend testing for people who have a strong family history of a type of cancer that is known to be linked to these genes: breast cancer before the age of 45, several family members with the disease on the same side of the family, breast cancer and ovarian or pancreatic cancer on the same side of the family, a family history of male breast cancer, or Jewish ancestry combined with even one case of breast or ovarian cancer in the family.
Matloff emphasized that most cases of breast and ovarian cancer are not related to these mutations.
How does the test work?
Generally, a woman who is concerned about her cancer risk begins by consulting her physician and a genetic counselor, who can examine her personal and family history to determine what tests might be useful. A genetic counselor can also discuss the pros and cons of testing, including implications for other family members, Matloff said.
The test involves collecting a sample of blood or saliva and sending it to Myriad Genetics, a company that performs the analysis and can deliver a report on which variants you have and how much these variants increase your risk of various types of cancer.
However, Matloff warned that sometimes the test results were misinterpreted, with variants that are not known to cause cancer confused with variants that do. "We've found that a lot of women who've had this surgery had their test results read incorrectly," she said.
If the test says I have a high risk of breast cancer, should I have my breasts removed?
That is a very personal decision that patients should make in consultation with their families and doctors. Cosmetic factors and the availability of other options — including heightened surveillance for early signs of disease or taking a drug such as tamoxifen, Matloff said — can come into play as a woman makes her decision.
Nagy said that studies had estimated that at least 35% of women who have a dangerous BRCA mutation decide to get the surgery when they are still healthy. Doing so can reduce their lifetime risk of breast cancer to less than 5%.
Why doesn't it reduce the risk to 0%?
Even after a double mastectomy, some breast cells remain — and there is always a chance that cancer could develop in this tissue, Matloff said. However, a risk of less than 5% is much lower than the 12% to 13% risk faced by a typical American woman, she added.
What is involved in a mastectomy?
All mastectomies involve removal of most of the breast tissue, but patients have options when deciding whether or how to have their breasts reconstructed, said Dr. Maureen Chung, a surgeon and medical director of the Margie Petersen Breast Center at St. John's Health Center in Santa Monica.