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Amount of Risk Reduction from Protective Ovary Removal Depends on Type of BRCA Abnormality

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Women with an abnormal BRCA1 or BRCA2 gene have a much higher than average risk of both breast and ovarian cancers. One aggressive way to lower the risk of both cancers is to remove the ovaries. This is called prophylactic (protective) oophorectomy (oo-for-EK-tuh-mee).

A study shows that the amount of breast and ovarian cancer risk reduction after prophylactic ovary removal varies depending on the type of gene abnormality.

In women with an abnormal BRCA1 gene, removing the ovaries was more beneficial for lowering ovarian cancer risk (risk was reduced by 85%) than for lowering breast cancer risk (39% risk reduction).

In women with an abnormal BRCA2 gene, removing the ovaries was beneficial for lowering breast cancer risk (72% risk reduction), but the researchers couldn't tell how much it reduced ovarian cancer risk.

The large study looked at more than 1,000 women with either an abnormal BRCA1 or BRCA2 gene. The women decided to have either prophylactic ovary removal or to be monitored by their doctors.

Ovary removal and breast cancer risk:

Women who DON'T have an inherited breast cancer gene abnormality have about a 12% risk of developing breast cancer over their lifetimes. Women who DO have an abnormal BRCA1 or BRCA2 gene have up to an 85% risk of developing breast cancer by age 70. This study found that lowering breast cancer risk by removing the ovaries before menopause was less beneficial for women with an abnormal BRCA1 gene compared to women with an abnormal BRCA2 gene.

Removing the ovaries gets rid of the main source of hormones that can make hormone-receptor-positive breast cancers grow. Removing the ovaries may not be as beneficial for women with an abnormal BRCA1 gene because these breast cancers are much more likely to be hormone-receptor-negative. Breast cancers in women with an abnormal BRCA2 gene are more likely to be hormone-receptor-positive. This might explain why the study found more breast cancer risk reduction from ovary removal in women with an abnormal BRCA2 gene.

Ovary removal and ovarian cancer risk:

Women who DON'T have an abnormal BRCA1 or BRCA2 gene have less than a 2% risk of developing ovarian or other gynecologic cancer during their lifetimes. Women who have an abnormal BRCA1 gene have a lifetime ovarian cancer risk of about 55% (if they don't take steps to lower their risk). Women who have an abnormal BRCA2 gene have a lifetime ovarian cancer risk of about 25%. This study found that the reduction in ovarian and related cancers risk from ovary removal before menopause wasn't as large or as certain in women with an abnormal BRCA2 gene, compared to women with an abnormal BRCA1 gene. The researchers weren't sure why this was the case.

If you learn that you have an abnormal BRCA1 or BRCA2 gene, talk your doctor about ALL of the options that can lower your risk for both breast and ovarian cancer. Removing the ovaries is only one option. Some women may decide to have prophylactic removal of both breasts. There are also medicine options, depending on your menopausal status. Medicines can be used to shutdown the ovaries and hormonal therapies can block estrogen effects or lower estrogen production. Together, you and your doctor can decide on the best risk reduction plan for your unique situation.

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