In premenopausal women, most of the estrogen in the body is made by the ovaries. Because estrogen makes hormone-receptor-positive breast cancers grow, reducing the amount of estrogen in the body or blocking its action can help shrink hormone-receptor-positive breast cancers and reduce the risk of hormone-receptor-positive breast cancers coming back (recurring).
In some cases, the ovaries (and usually the fallopian tubes) may be surgically removed to treat hormone-receptor-positive breast cancer or as a risk-reduction measure for women at very high risk of breast cancer. This is called prophylactic or protective ovary removal, or prophylactic oophorectomy. Removing the ovaries is one way to permanently stop the ovaries from producing estrogen. Medicines also can be used to temporarily stop the ovaries from making estrogen (called medical shutdown). Ovarian shutdown with medication or surgical removal is only for premenopausal women.
Prophylactic ovary removal
A 2008 study shows that premenopausal women who had their ovaries removed and took tamoxifen for 5 years after breast cancer surgery had a lower risk of the breast cancer coming back and better survival rates compared to premenopausal women who didn't have their ovaries removed and took tamoxifen after surgery. While this is considered aggressive treatment because it puts you prematurely and permanently in menopause, it may be a good treatment option for women who don't want to have any more biological children or for women who are at high risk for the cancer coming back.
While most of the estrogen in a woman's body is made by the ovaries, smaller amounts of estrogen are made in other parts of the body; a steroid produced by the adrenal glands (androgen) is made into estrogen in fat tissue. This is why you still might take tamoxifen after prophylactic ovary removal — to block the effect of any estrogen in your body.
Many studies show that prophylactic ovary removal reduces the risk of breast cancer among high-risk women who haven't been diagnosed with disease. Being high-risk usually means you've tested positive for an abnormal BRCA1 or BRCA2 gene, genes linked to breast cancer. Being high-risk also can mean that you have a strong family history of breast cancer, ovarian cancer, or both.
According to the National Cancer Institute, prophylactic ovary removal would reduce the number of new breast cancer cases among high-risk women by 50%. This benefit occurs only if the ovary removal is performed before menopause. Removing the ovaries before menopause significantly reduces the level of estrogen in a woman’s body. A 2008 study showed that reduction in breast cancer risk after ovary removal is higher in women with an abnormal BRCA2 gene.
For more information, please visit the Prophylactic Ovary Removal section.
Medical shutdown of the ovaries
Medicines can be used to temporarily stop the ovaries from making estrogen. Two of the most common ovarian shutdown medicines are:
- Zoladex (chemical name: goserelin)
- Lupron (chemical name: leuprolide)
Zoladex and Lupron are both luteinizing hormone-releasing hormone (LHRH) agonists. These medicines work by telling the brain to stop the ovaries from making estrogen. The medicines are given as injections once a month for several months or every few months. Once you stop taking the medicine, the ovaries begin functioning again. The time it takes for the ovaries to recover can vary from woman to woman.
Women who want to bear children after breast cancer treatment may prefer medical shutdown of the ovaries over surgical ovary removal.
There have been cases of women getting pregnant while on these medications, so if you are premenopausal and have a male partner, it's important to use non-hormonal birth control such as condoms, a diaphragm, or a non-hormonal I.U.D.
Deciding to have your ovaries shut down with medicine or surgically removed requires a lot of careful thought and discussion with your doctor. Tell your doctor about any fertility concerns you may have. Together you can weigh the benefits and the risks against each other and decide on the best option for you and your unique situation.