Current or recent past users of hormonal replacement therapy (HRT) have a higher risk of being diagnosed with breast cancer. Before the link between HRT use and breast cancer risk was established, many postmenopausal women took HRT for many years to ease menopausal symptoms (hot flashes, fatigue) and to reduce bone loss. Since 2002, when research linked HRT and risk, the number of women taking HRT has dropped dramatically. Still, many women continue to use HRT to handle bothersome menopausal symptoms.

There are two main types of HRT:

combination HRT contains the hormones estrogen and progesterone

estrogen-only HRT contains only estrogen

Each type of HRT seems to have a different effect on breast cancer risk.

Combination HRT increases breast cancer risk by about 75%, even when used for only a short time. Combination HRT also increases the likelihood that the cancer may be found at a more advanced stage, as well as increasing the risk that a woman diagnosed with breast cancer will die from the disease. Breast cancer risk increases the most during the first 2 to 3 years of taking combination HRT. Higher-dose combination HRT increases breast cancer risk more than lower-dose combination HRT. Breast cancer risk goes back down to average about 2 years after you stop taking combination HRT.

Estrogen-only HRT increases the risk of breast cancer, but only when used for more than 10 years. Estrogen-only HRT also can increase the risk of ovarian cancer.

The higher breast cancer risk from using HRT is the same for so-called "bioidentical" and "natural" hormones as it is for synthetic hormones. "Bioidentical" means the hormones in the product are identical to the hormones your body produces. Bioidentical hormones are said to be "natural" -- derived from plants. Synthetic hormones are made in a lab and are also chemically identical to the hormones in your body. It's important to know that many herbal and bioidentical HRT products fall outside the jurisdiction of the United States Food and Drug Administration and so aren't subject to the same regulations and testing that medications are.

Steps you can take

Menopausal side effects can dramatically reduce quality of life for some women. These women have to weigh the benefits of HRT against the risks. If you're having severe hot flashes or other menopausal side effects and are considering HRT, talk to your doctor about ALL of your options. Ask how you can minimize your breast cancer risk AND relieve your symptoms. Be sure to discuss the pros and cons of different types of HRT. Research strongly suggests that estrogen-only HRT appears to increase breast cancer risk less than combination HRT. If you do decide to take HRT, ask if you can take a lower-dose formula and talk to your doctor about taking it for the shortest time possible.

If you've been diagnosed with breast cancer or have tested positive for an abnormal breast cancer gene (BRCA1 or BRCA2) and so are at high risk, you shouldn't use HRT. The hormones in HRT can cause hormone-receptor-positive breast cancers to develop and grow. While only a few small studies have looked at HRT use in women with a personal history of breast cancer, the fact that HRT use increases breast cancer risk among women in general makes almost all doctors advise women with a personal history of breast cancer to avoid HRT. The prescribing sheet included with HRT clearly states that it is "contraindicated in women with a diagnosis of breast cancer." Not being able to use HRT can present a challenge for many women. If you're having severe hot flashes or other menopausal side effects and have a personal history of breast cancer, talk to your doctor about non-hormonal options, such as dietary changes, exercise, weight management, acupuncture, or meditation.

For more information on hot flashes and how to manage them, visit the Breastcancer.org Menopause Symptoms: Hot Flashes page.

Whether or not you take HRT, there are also lifestyle choices you can make to keep your breast cancer risk as low as it can be:

These are just a few of the steps you can take. Review the links on the left side of this page for more options.

Think Pink, Live Green: A Step-by-Step Guide to Reducing Your Risk of Breast Cancer teaches you the biology of breast development and how modern life affects breast cancer risk. Download the PDF of the booklet to learn 31 risk-reducing steps you can take today.