Breast Cancer: Hormone Replacement Therapy and Cancer Risk

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Friday, 28 December 2007

Hormone replacement therapy (HRT) is used to relieve menopause symptoms, especially hot flashes. A woman on hormone therapy usually takes both estrogen and progestin (typically a synthetic form of progesterone). Women who have had a hysterectomy can take estrogen alone. Estrogen relieves hot flashes and prevents osteoporosis, but estrogen can increase your risk of developing uterine cancer. Progestin is added in women with a uterus to prevent this.

Many studies have looked at the association between hormone 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 include 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.

If a woman no longer has a uterus, estrogen alone can be given for symptoms of menopause. This probably does not increase the 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 a woman is faced with menopause and hot flashes, she and her doctor should discuss the risks and benefits and decide if treatment should included hormone therapy or not.

Do the Benefits of Hormone Therapy Outweigh the Risk?

Hormone 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 healthcare 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 can 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 may be too risky to treat breast cancer survivors with HRT.

Alternative Options for Hormone Therapy to Protect your Bones From Osteoporosis

Selective estrogen receptor modulators (SERMs) are a newer class of drugs similar to estrogen that protect against osteoporosis by increasing bone density, while perhaps also protecting against the development of breast cancer.

Raloxifene (Evista) is a widely used SERM that has been shown to increase bone growth and density. Unfortunately it does not relieve symptoms of menopause, such as hot flashes and may actually worsen them. Although the FDA has approved this drug for osteoporosis prevention, studies are currently being done to investigate its use in breast cancer prevention and treatment.

Additional interventions that may prevent or treat osteoporosis include weight bearing exercises, other prescription medications and taking calcium and vitamin D supplements daily.

Reviewed by the doctors at The Cleveland Clinic Taussig Cancer Center.

WebMD Medical Reference provided in collaboration with the Cleveland Clinic