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Hormonal therapies are drugs that block oestrogen from attaching to breast cancer cells or lower the level of oestrogen in the body. Oestrogen can encourage some breast cancer cells to grow.
Hormonal therapies are commonly prescribed in women with invasive breast cancer because they reduce the risk of breast cancer coming back. Hormonal therapies are only effective in women whose cancer cells have receptors for oestrogen on their surface. This is known as being oestrogen-receptor positive (ER positive).
Because doctors don’t know enough about the benefits of hormonal therapies in DCIS, they are only usually given in a research trial|.
Tamoxifen| is a commonly used hormonal therapy. It’s widely used in women with early, invasive breast cancer who haven’t had their menopause and in some women who have. The National Institute for Health and Clinical Excellence (NICE) currently advises the NHS on the best treatments and drugs to use. NICE recommends that tamoxifen is used within a research trial to treat women with DCIS.
Tamoxifen is taken daily as a tablet, usually for 3–5 years.
Some trials have shown that tamoxifen reduces the risk of DCIS coming back. It can also reduce the risk of invasive cancer in the treated and other breast. However, other trials don’t show the same benefit.
Occasionally, some specialists recommend taking tamoxifen outside a research trial. Your specialist will explain the possible advantages of tamoxifen in your individual situation. You may need time to talk things over with your doctor, nurse or family before making a decision.
Common side effects are:
For many women, these side effects are mild and can reduce over time. But in some women, side effects can continue to be troublesome. If this happens, talk to your doctor or nurse. Some of the side effects of tamoxifen are similar to the symptoms of the menopause. You can read more about coping with these in our section on breast cancer and menopausal symptoms|.
For women who’ve been through menopause, tamoxifen can slightly increase the risk of womb (endometrial) cancer, blood clots in the leg and strokes. Although this sounds frightening, these effects are very rare. If they occur they’re usually picked up very early when they can be successfully treated.
Because doctors don’t know enough about the benefits of hormonal therapy in DCIS, you may be asked to take part in a treatment research trial. The IBIS II (DCIS) trial is comparing tamoxifen with another drug called anastrazole| (Arimidex®), which is an aromatase inhibitor.
Aromatase inhibitors are another type of hormonal therapy and are only effective in women who’ve been through the menopause.
If you’ve had a mastectomy, you have almost no risk of DCIS coming back. You may be asked to think about taking part in a trial (the IBIS prevention trial) to find out if anastrozole lowers the risk of cancer in your remaining breast.
Content last reviewed: 1 February 2011
Next planned review: 2013
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