← Breastcancer.org

Diagnosed Women with Abnormal Breast Cancer Gene Have Higher Risk of New Cancer in Opposite Breast

Sign in to receive recommendations (Learn more)

Most inherited cases of breast cancer are associated with one of the two abnormal breast cancer genes: BRCA1 and BRCA2. Women with an abnormal BRCA1 or BRCA2 gene have up to an 85% risk of developing breast cancer by age 70. Abnormal BRCA1 and BRCA2 genes are found in 5% to 10% of all breast cancer cases in the United States. When a woman with an abnormal BRCA gene is diagnosed with breast cancer, her short- and long-term treatment must consider two risks:

  • the risk of the first cancer coming back in the same breast
  • the risk of a new cancer developing in the opposite breast (contralateral breast cancer)

A study suggests that women with an abnormal BRCA1 or BRCA2 gene who have been diagnosed with breast cancer are 4 times more likely to be diagnosed with a new cancer in the opposite breast compared to women without an abnormal breast cancer gene diagnosed with breast cancer. The risk of a new cancer in the opposite breast is highest for women with an abnormal breast cancer gene who were initially diagnosed before age 40.

This study followed 1,398 women diagnosed with breast cancer in one breast and 705 women diagnosed with cancer in one breast and then a second cancer in the opposite breast. All the women were tested for abnormal BRCA1 and BRCA2 genes and all were first diagnosed before age 55. Diagnoses of new cancer in the opposite breast were made at least 1 year after the first diagnosis. The researchers wanted to know if there was a difference in the risk of developing a new cancer in the opposite breast 5 and 10 years after the first diagnosis based on BRCA1 or BRCA2 status.

At 5 years after first diagnosis:

  • 9.7% of women with an abnormal breast cancer gene developed cancer in the opposite breast compared to 2.5% of women without an abnormal breast cancer gene
  • 10.9% of women with an abnormal BRCA1 gene developed cancer in the opposite breast compared to 8.3% of women with an abnormal BRCA2 gene

Younger women with an abnormal breast cancer gene had the highest risk of developing cancer in the opposite breast:

  • women with an abnormal breast cancer gene first diagnosed between 25 and 39 had a 15.5% risk of developing cancer in the opposite breast; women without an abnormal breast cancer gene first diagnosed at the same age had a 3.2% risk of developing cancer in the opposite breast
  • women with an abnormal breast cancer gene diagnosed between 50 and 54 had a 5.6% risk of developing cancer in the opposite breast; women without an abnormal breast cancer gene first diagnosed at the same age had a 2.3% risk of developing cancer in the opposite breast

At 10 years after first diagnosis:

  • 18.4% of women with an abnormal breast cancer gene developed cancer in the opposite breast compared to 4.9% of women without an abnormal breast cancer gene
  • 20.5% of women with an abnormal BRCA1 gene developed cancer in the opposite breast compared to 15.9% of women with an abnormal BRCA2 gene

Younger women with an abnormal breast cancer gene still had the highest risk of developing cancer in the opposite breast:

  • women with an abnormal breast cancer gene first diagnosed between 25 and 39 had a 31% risk of developing cancer in the opposite breast
  • women with an abnormal breast cancer gene diagnosed between 50 and 54 had a 10.8% risk of developing cancer in the opposite breast

These results support other studies that have shown women with an abnormal breast cancer gene who have been diagnosed with breast cancer have a much higher risk of developing a new cancer in the opposite breast compared to women without an abnormal breast cancer gene. After a breast cancer diagnosis, women with an abnormal breast cancer gene should consider this increased risk when developing treatment and screening plans with their doctors.

One very aggressive risk reduction option is removing the healthy breast (called contralateral prophylactic mastectomy). Research has shown that removing the healthy breast greatly lowers the risk of cancer being diagnosed in that breast area in the future.

If you have an abnormal breast cancer gene and have been diagnosed with breast cancer, you and your doctor need to consider the risks associated with an abnormal breast cancer gene as well as the specific characteristics of the cancer and your preferences as you develop your treatment and screening plans.

Deciding to have the healthy breast removed also may make sense for you as you try to do all you can to reduce your future risk. Still, you may want to talk to your doctor about ALL of your risk reduction options. Contralateral prophylactic mastectomy is only one of these options and is a very aggressive step. While it may be the right decision for you, give yourself the time you need to consider your decision carefully. Prophylactic mastectomy doesn't have to be done at the same time as lumpectomy or mastectomy. Together, you and your doctor can make the decisions that are best for you and your unique situation.

Evergreen-donate
Back to Top