Genetic Assessment for Breast Cancer

Genetics and breast cancer

Most people who develop breast cancer have no known risk factors and no family history of the disease. However, about 5 to 10 percent of people with breast cancer have a gene mutation (difference in a gene) that they inherited from their mother, father, or both parents, causing an increased risk for developing cancer.

Multiple genes are tied to breast cancer, though the 2 most commonly known are breast cancer genes 1 and 2 (BRCA1 and BRCA2). Normally, when these genes aren’t mutated, they produce proteins that help repair DNA and control cell growth, preventing tumors from forming. But inherited mutations in either gene can cause cells to grow abnormally and out of control, leading to cancer.

BRCA gene mutations and cancer risk

Inheriting a BRCA1 or BRCA2 mutation significantly increases a person’s risk of developing breast cancer. However, not everyone who inherits a gene mutation will develop the disease.

According to the National Cancer Institute, the likelihood of developing breast cancer is:

  • Average person: About 8 percent of women by age 70
  • Women with a BRCA1 mutation: 47-66 percent by age 70
  • Women with a BRCA2 mutation: about 40-57 percent by age 70

BRCA1 and BRCA2 mutations increase men’s risk of developing breast cancer, too. Both women and men with a BRCA mutation also have a higher risk for other cancers, including:

  • Women: Gynecologic cancers such as fallopian tube and ovarian cancer
  • Men: Prostate cancer
  • Both: Melanoma (the most serious type of skin cancer)
  • Both: Pancreatic cancer

What is genetic testing for breast cancer risk?

Genetic testing is done by a blood or saliva test. The blood or saliva sample is analyzed by a medical test that identifies changes in genes, chromosomes, or proteins. For breast cancer, genetic testing can show whether someone has inherited mutations in genes related to the disease — BRCA1, BRCA2, and others.

We often use multi-gene testing to look for other gene mutations related to inherited risk for breast cancer. Some of these other mutations have lower cancer risks than BRCA and some have risks about the same.

Before undergoing any genetic tests, talk to your doctor and a genetic counselor to understand the risks and benefits, as well as other issues.

Who should consider genetic testing?

Inherited cancer risk gene mutations are fairly rare. Medical experts recommend testing for people who have specific risk factors, including:

  • Family member (parent, sister or brother, child, grandparent, grandchild, uncle, aunt, or first cousin) with an inherited gene mutation related to breast cancer, including BRCA1 or BRCA2
  • Personal history of breast cancer at age 45 or younger
  • Close family member history of breast cancer at age 45 or younger
  • Personal history of breast cancer at any age, plus 2 or more close family members on the same side of the family diagnosed with breast, pancreatic, or aggressive prostate cancer
  • Ashkenazi Jewish heritage and a personal history of breast or pancreatic cancer
  • Personal or family history of ovarian cancer
  • Personal or family history of male breast cancer

If you have your family’s medical history, you can bring it to your first appointment. If not, your doctor will discuss your personal medical history with you and help you decide if you want to get genetic testing. Our genetic counselors can help with family communication and work with you to gather the history.

Why have genetic testing?

Whether the results show a gene mutation or not, genetic testing can benefit you and your family. The results can:

  • Identify the level of cancer risk a person may have and the types of cancer for which they may be at risk
  • Provide information to guide decision-making for cancer prevention and early detection
  • Identify family members who are at high risk, as well as those who are not
  • Improve the chances of survival of family members who already have breast cancer, by providing information to guide treatment choice

Cancer genetic counseling at Stanford

At Stanford, our Cancer Genetics Program has genetics physicians and licensed genetic counselors to help you understand genetic testing. They can help you decide whether it’s right for you and your family.

What to expect during your first appointment

One of our genetic counselors will meet with you to review your personal and family history, assess your risk, review testing options and discuss possible outcomes. We talk over what the results may mean for you and your family, and who else in your family may need testing if the results find a mutation.

The appointment lasts about 1 hour. If you choose to have genetic testing, we take a blood or saliva sample to collect your DNA for testing. It takes about 2-4 weeks to get the test results. The counselor will call you with the results.

If the results show a mutation, the next step is to meet with the counselor and a cancer genetics doctor. During this visit, we will:

  • Explain your test results
  • Provide medical recommendations
  • Discuss the implications for you and your family members

Contact the Cancer Genetics team

If you are considering genetic testing for breast cancer or have questions, talk with your doctor or call us at 650-498-6000.

Cancer Genetics Program in Palo Alto
Stanford Cancer Center
900 Blake Wilbur Drive
Palo Alto, CA 94304
Phone: 650-498-6000

Cancer Genetics Program in San Jose
Stanford Cancer Center South Bay
2589 Samaritan Drive
San Jose, CA 95124
Phone: 650-498-6000

Cancer Genetics Program at Stanford Valley Care
5565 W. Las Positas Blvd.
Pleasanton, CA 94588

Stanford Health Library

For confidential help with your health care questions, contact the Stanford Health Library. Professional medical librarians and trained volunteers can help you access journals, books, e-books, databases, and videos to learn more about medical conditions, treatment options, and related issues.

  • 875 Blake Wilbur Drive, Palo Alto: First floor near the cafe, 650-736-1960
  • South Bay Cancer Center: 2589 Samaritan Drive, third floor lobby, 408-353-0197

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