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Women With Abnormal BRCA Gene Have Higher Risk of New Cancer in Opposite Breast

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A Dutch study has found that women with an abnormal BRCA1 or BRCA2 gene who've been diagnosed with breast cancer have a higher risk of being diagnosed with a new, different cancer in the opposite breast (contralateral breast cancer) compared to women without an abnormal BRCA1 or BRCA2 gene.

The results were presented at the 2011 San Antonio Breast Cancer Symposium.

Most inherited cases of breast cancer are associated with one of two abnormal genes: BRCA1 (BReast CAncer gene one) or BRCA2 (BReast CAncer gene two).

Women with a mutation in the BRCA1 or BRCA2 gene:

  • have up to an 72% lifetime risk of developing breast cancer
  • have a much higher-than-average lifetime risk of ovarian cancer; estimates range from 17% to 44%

The BOSOM trial tracked the outcomes of 5,065 women diagnosed with invasive breast cancer before age 50. About 4% of the women had an abnormal BRCA gene:

  • 3% had an abnormal BRCA1 gene
  • 1.1% had an abnormal BRCA2 gene

After 10 years, contralateral breast cancer was diagnosed in:

  • 20% of women with an abnormal BRCA1 gene
  • 11% of women with an abnormal BRCA2 gene
  • 6% of women with no abnormal breast cancer gene

The results aren't really surprising since the higher risk of breast cancer associated with an abnormal BRCA gene applies to both breasts. Other research also has shown that women with an abnormal BRCA1 or BRCA2 gene who've been diagnosed with breast cancer also have a higher risk of developing a new, second breast cancer compared to women who don't have an abnormal breast cancer gene.

If you have an abnormal breast cancer gene and have been diagnosed with breast cancer, you and your doctor need to consider your risk of developing a new cancer as well as your preferences as you develop your treatment plan. Choosing to have the opposite healthy breast removed is one option you may consider to reduce your risk of contralateral breast cancer. This is called contralateral prophylactic mastectomy.

Deciding to have the opposite healthy breast removed 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.

You can learn more about BRCA1 and BRCA2 gene abnormalities on the Risk Factors: Genetics page.

Editor’s Note: This article was updated on Jan. 24, 2019, with updated information on cancer risk associated with BRCA mutations.

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