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There is a new group of drugs that is being recommended for
use in postmenopausal women with advanced breast cancer. The drugs, Arimidex (anastrozole)
and Femara (letrozole), are called aromatase inhibitors (AIs).
How do these drugs work?
Aromatase is an enzyme that helps the body produce the
hormone estrogen. AIs work in a different way than tamoxifen. While tamoxifen
blocks estrogen receptors, AIs block the action of aromatase.
After menopause, a woman's main source of estrogen comes
through a process called aromatization, in which male hormones called androgens
(produced by the adrenal glands located at the top of the kidneys), are
converted into estrogen. This process takes place throughout the body, in the
fatty tissue.
In some women, the hormone estrogen causes the breast cancer
to grow faster. Thus, aromatase inhibitors fight breast cancer growth by
stopping the conversion of androgens into estrogen.
Both tamoxifen and aromatase inhibitors are only effective for
treating cancers that use hormones to help the tumors grow and are thus called
hormone therapy. These cancers are known as hormone receptor positive.
Another new drug, Aromasin (exemestane), is similar to the AIs
but is an aromatase inactivator. Instead of blocking the aromatase, aromatase
inactivators actually destroy the enzyme.
What is hormone therapy?
Hormones are chemicals produced by glands in the body
and are circulated in the blood. Hormone therapy -- also called hormonal therapy
or hormone treatment -- is any treatment that adds, blocks, or removes hormones.
For certain conditions (such as diabetes or menopause), hormones are given to
boost low hormone levels. Sometimes, hormone therapy is used to slow or stop the
growth of certain cancers (such as prostate and breast cancer). The female
hormones estrogen and progesterone, for example, promote the growth of some
breast cancer cells. So hormone therapy may be given to block the body's
naturally occurring estrogen and fight the cancer's growth. Sometimes surgery is
needed to remove the source of the hormone in question -- in the case of breast
cancer, the ovaries may be removed.
When are these drugs prescribed?|
Aromatase inhibitors delay the progression of breast
cancer longer than tamoxifen in women with advanced breast cancer whose tumors
rely on estrogen to grow. Specifically, Femara and Arimidex are used as part of
the initial or follow-up treatment of hormone-sensitive breast cancer (even
those that have spread to other parts of the body in women who have gone through
menopause). They are pills that are taken once a day. Femara was also discovered
to be beneficial after taking tamoxifen for 5 years. Aromasin is currently used
to treat postmenopausal women with breast cancer that has spread outside of the
breast that was not responsive to tamoxifen. It's a pill taken once a day after
meals. These drugs also show promise as additional therapy for early breast
cancer.
What are the side effects?
- Nausea
- Fluid retention and/or weight gain
- Headache
- Joint aches or pains
This list of side effects does not include all possible side
effects, and not all people who take these drugs will experience these side
effects. Always contact your doctor if you have questions about your personal
situation.
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