Menopausal Hormone Therapy and Breast Cancer

Ask the Expert

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Does menopausal hormone therapy cause breast cancer or not?


This is a complicated and controversial issue, one that you should speak with your health care provider about if you are considering menopausal hormone therapy.

While we can't say that menopausal hormone therapy (HT) causes breast cancer, we do know that hormones can play an important role in cancer growth and may increase a woman's chances of having the disease. In 2002, the Women's Health Initiative (WHI) halted part of a large clinical study after finding that women taking estrogen plus progestin had an increased risk (a relative risk of 24 percent, but an absolute risk of 2 per 1,000 women) of developing breast cancer. While this increase may sound like a lot, it's still a small risk. For example, if your overall risk is 12 percent, taking combination estrogen-progestin only increases your risk by 2.9 percent.

It's also important to keep in mind that these results relate to this specific HT regimen (estrogen plus progestin); women who were taking estrogen only had no increased breast cancer risk, in fact there were fewer breast cancer seen after 6.7 years of estrogen only compared to placebo.

Interestingly, after increasing for decades, the rate of new breast cancer cases started to decline between 2001 and 2004, which many researchers believe may partly reflect the reduced use of HT by millions of women after the results of the WHI study were widely reported. Because estrogen fuels most breast cancers, researchers suspect this sudden withdrawal may be slowing the growth of miniscule tumors too small to be seen on mammogram, at least in the short term. Breast cancer may also be found at a more advanced stage in women on certain HT treatments.

As with most medication therapy, HT has benefits and risks. Although there are risks to hormone therapy, including an increased risk of breast cancer, heart disease, stroke and blood clots, most health care professionals agree that hormone therapy is still appropriate for perimenopausal and recently menopausal women with moderate to severe symptoms (for example, hot flashes, sleep disturbances, night sweats and vaginal changes). HT has also been used for years to prevent osteoporosis (a thinning and weakening of the bones) for women at high risk of the condition.

To make informed decisions about HT, it's important that you know your individual risk of breast cancer, taking into account your age, race, age of menarche, age at first pregnancy, family history and previous breast biopsies. Be sure to talk openly with your health care provider about your personal risk for breast cancer, especially if you have a strong family history, specific peri- and postmenopausal symptoms you are experiencing and any concerns you have about HT. There are more than 20 varieties of hormone therapy on the market, so you have plenty of options. Some regimens are more effective in treating certain symptoms. Discuss the risks and benefits of different types of therapy with your health professional.

If you decide to take hormone therapy, you may want to start at the lowest dose for the shortest amount of time needed to gain relief. However, if you need to, you can use hormone therapy for an extended length of time.

Bottom line: Only you and your health care provider can decide if hormone therapy is right for you, which type is best and for how long you should use it.

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