Breast Cancer Health Center

Hormone Replacement Therapy and Breast Cancer Risk

Hormone replacement therapy, also referred to as HRT, is used to relieve menopause symptoms, especially hot flashes and osteoporosis. A woman on hormone therapy usually takes both estrogen and progestin. Women who have had a hysterectomy can take estrogen alone. Estrogen relieves hot flashes and prevents osteoporosis. However, estrogen alone can increase your risk of developing uterine cancer.  

Many studies have looked at the association between hormone replacement therapy and breast cancer. The best evidence for the benefits and risks of hormone replacement therapy come from the Women's Health Initiative (WHI), a large study involving more than 16,000 healthy women. The results published in July 2002 showed the risks of combined HRT with estrogen plus progestin outweigh the benefits. These risks included an increase in breast cancer, heart disease, stroke, and blood clots. 

Not only does combined HRT increase the risk of developing breast cancer, but it also increases the chances that the cancer will be discovered at a more advanced stage. This is due to its influence in reducing the effectiveness of mammography by creating denser breast tissue.

If you no longer have a uterus, estrogen alone can be given for symptoms of menopause. This probably does not increase your risk of developing breast cancer much, if at all. In March 2004, it was concluded from the WHI study that those taking estrogen only had no increased risk of breast cancer or heart disease, however estrogen does appear to increase one's risk of stroke.

If you are considering HRT to relieve your menopausal symptoms, talk to your doctor to discuss the risks and benefits. Together you can decide what is right for you.  

Do the Benefits of HRT Outweigh the Risk?

Hormone replacement therapy is an effective treatment for relieving hot flashes from menopause. But the known link between hormone therapy and increased breast cancer risk has discouraged many women and their doctors from choosing or recommending this treatment.

The type of hormone therapy (estrogen only or combination of estrogen and progestin), as well as the woman's individual characteristics, risk factors, and severity of menopause symptoms, should be considered when weighing the risks and benefits of HRT. The decision to use hormone therapy after menopause should be made by a woman and her health care provider after weighing all of the potential risks (including heart disease, breast cancer, stroke, and blood clots) and benefits (relief of menopause symptoms and prevention of osteoporosis).

The known association between HRT and breast cancer has prevented many breast specialists from recommending it for breast cancer survivors. Unfortunately, many women experience menopause symptoms after breast cancer treatment. Some forms of chemotherapy may also cause early menopause in premenopausal women.

In the past, doctors had offered HRT after breast cancer treatment because there weren't clear cut studies showing any harm. However, early in 2004, a study (the HABITS study) was stopped early after it was shown that cancer survivors on HRT were more likely to develop a new or recurrent breast cancer. Doctors now feel it is too risky to treat breast cancer survivors with HRT.