BRCA Testing: What You Need to Know

Written by: Lukas Harnisch-Weidauer
Medically Reviewed By: Judy E. Garber, MD, MPH

What are the BRCA genes?

The BRCA1 and BRCA2 genes play a big role in preventing cancer. They belong to a class of genes called tumor suppressors, which ensure that cells don’t grow or divide too rapidly by fixing naturally occurring errors in DNA from reproduction during cell division.  

BRCA testing checks for mutations in both genes and can help people decide what steps they can take to reduce their cancer risk if they do test positive for a mutation. They are the most frequently altered gene in individuals in families with breast, ovarian, pancreas or prostate cancers, but there are other related genes that are often included when testing is performed. 

What is the relationship between BRCA mutations and cancer? 

If one copy of a BRCA gene has a mutation, it won’t function correctly and can increase someone’s risk of developing certain cancers, including breast or ovarian cancer. About 50 out of 100 women who have a BRCA1 or BRCA2 mutation will develop breast cancer and 30 out of 100 of these women will develop ovarian cancer by age 70. Overall, about five to 10 percent of breast cancer diagnoses and about 15 percent of ovarian cancer diagnoses are related to a BRCA mutation. 

Variants in the BRCA gene are usually present in every cell of the body and can be found through a blood test. However, the copies of the genes in breast, ovary and other cells are most important to the development of cancers in those organs. The reason that the risk of cancer is mostly limited to several sites is still a mystery. 

The BRCA1 and BRCA2 genes  belong to a class of genes called tumor suppressors, which ensure that cells don’t grow or divide too rapidly by fixing naturally occurring errors in DNA from reproduction during cell division. 
The BRCA1 and BRCA2 genes belong to a class of genes called tumor suppressors, which ensure that cells don’t grow or divide too rapidly by fixing naturally occurring errors in DNA from reproduction during cell division. 

What is the difference between BRCA1 and BRCA2 mutations? 

The two genes indicate different levels of risk that patients have in developing breast, ovarian, pancreatic, or prostate cancer. 

A study published in 2015 tracked breast and ovarian cancer occurrences over a 75-year period in 31,000 women who had inherited BRCA mutations. The researchers found that mutations at either end of the BRCA1 gene increased the risk of breast cancer more than the risk of ovarian cancer. A group of mutations that occur in the middle portion of the gene, by contrast, raised ovarian cancer risk more than breast cancer risk. 

Investigators also found that if the mutation altered the length of the protein derived from the BRCA2 gene, there was a higher risk of developing ovarian cancer and other gynecologic cancers. 

Recent research has revealed that BRCA genes play a role in other cancers as well. A mutation of the BRCA2 gene has been found to be associated with a higher risk of prostate cancer, especially in men under the age of 65. BRCA1 and BRCA2 are also linked to a greater likelihood of developing pancreatic cancer. 

Should I be tested for a BRCA mutation? 

In early 2024, the American Society of Clinical Oncology (ASCO) and the Society of Surgical Oncology (SSO), recommended that all people diagnosed with a new breast cancer under the age of 65 be tested for BRCA1/2 mutation.  

Certain patients with a new breast cancer diagnosis over 65 should also be tested if they: 

  • Are candidates for PARP inhibitor treatment. 
  • Have triple negative breast cancer. 
  • Have a personal or family history of a cancer-related mutation. 
  • Were assigned male at birth. 
  • Are of Ashkenazi Jewish ancestry or are a member of another population at increased risk for founder mutations. 

This is a departure from previous practice where testing was offered based on family history. Ultimately, the group of surgeons and medical oncologists at SSO and ASCO determined that many BRCA mutations were being overlooked. It’s important to partner with a specialist in clinical cancer genetics to understand why testing is being recommended and if a variant is detected. 

Should you have a mastectomy if you have a BRCA mutation? 

People who test positive for an inherited BRCA mutation may decide to take steps to reduce the chance that they’ll develop a new breast cancer, often by undergoing a bilateral (or double) mastectomy. This is a very personal decision. Some people may choose to have additional screening rather than a mastectomy.  

What percent of BRCA tests are positive? 

BRCA1 and BRCA2 mutations are inherited, meaning if your parent has a BRCA gene mutation, you have a 50 percent chance of having the mutation. However, harmful BRCA mutations are uncommon in the general population. About one in every 400 women in the United States has either a BRCA1 or BRCA2 gene mutation. 

BRCA testing checks for mutations in either gene, and can help people decide what steps they can take to reduce their cancer risk if they do test positive for a mutation. 

What do you do if you’ve tested positive for a BRCA mutation? 

Individuals who test positive for a BRCA mutation should be educated about the implications of their genetic risk, including screening recommendations. They can opt for more frequent breast exams, early breast imaging and screening, and preventative mastectomies, or enrollment in studies of medications designed to reduce breast cancer risk. 

People with BRCA1 mutations are also at increased risk of ovarian cancer and are recommended to undergo the removal of the ovaries and fallopian tubes once they are done having children or by age 35 to 40. Since the risk is lower and later for BRCA2 mutation, women who carry a BRCA2 variant should plan for removal of ovaries and fallopian tubes between ages 45 and 50.   

Dana-Farber’s WISP trial is determining whether ovarian cancer risk can be reduced by removing the fallopian tubes alone, and going back to remove the ovaries when women are closer to natural menopause. 

The Mellen and Eisenson Family Center for BRCA and Related Genes at Dana-Farber provides expert clinical care to patients with BRCA-mutated and BRCA-related cancers, regardless of tumor type. Over the past 20 years, Dana-Farber investigators have made critical discoveries, illuminating the role of these genes and how their dysfunction leads to cancer susceptibility. 

Genetic testing for BRCA and other cancer risk genes is available through the Cancer Genetics and Prevention Center. Dana-Farber offers outstanding interdisciplinary, inter-disease group collaboration. Our team of specialists works closely together to offer patients the latest therapies and clinical services, including access to innovative clinical trials. 

Patients can access the Center either as a new patient or as previously followed in a Dana-Farber disease center. Patients are evaluated by an appropriate designated expert Center physician and will undergo a genetic evaluation if indicated. Following expert evaluation, patients will receive recommendations for therapy and/or enter a clinical trial. Clinical samples and data collected from patients across disease centers will be used for focused correlative, translational, and laboratory-based investigation of BRCA and BRCA-related genes. 

Does having a BRCA mutation affect how cancer might be treated? 

Yes, having a BRCA mutation can impact the type of treatment you receive. Patients with inherited BRCA mutations, as well as those with acquired BRCA mutations only in their tumors, are increasingly likely to benefit from new classes of drugs such as PARP inhibitors and other cell cycle checkpoint inhibitors, as well as targeted agents alone or in combination with immunotherapies. Specialists at the Mellen and Eisenson Family Center for BRCA and Related Genes at Dana-Farber work closely together to offer patients the latest therapies and clinical services, including access to innovative clinical trials. 

About the Medical Reviewer

Judy E. Garber, MD, MPH

Dr. Garber is the Susan F. Smith Chair and Chief of the Division of Cancer Genetics and Prevention at Dana-Farber Cancer Institute and a Professor of Medicine at Harvard Medical School.  She conducts research in clinical cancer genetics, with a special focus in genetics of breast cancer.  Dr. Garber is also a leader in research into the characteristics and treatment of triple negative breast cancer, the most common form in women with BRCA1 mutations and an expert in Li-Fraumeni Syndrome.  Her translational research focuses on the evaluation of novel agents targeting DNA repair defects in breast cancer, including PARP inhibitors for treatment and prevention of breast cancer and other BRCA-associated cancers, and the study of other agents for reduction of breast cancer risk.

 

Dr. Garber is a past president of the American Association for Cancer Research (AACR).  She served on the National Cancer Advisory Board of the National Cancer Institute and was elected into the American Society of Clinical Investigation, the American Association of Physicians and the National Academy of Medicine.  She serves as the Scientific Director of the Breast Cancer Research Foundation and is a past chair of the Breast Cancer Research Foundation Scientific Advisory Board.  She is an ASCO Statesman and a Fellow of the AACR Academy, and was its first president.