When You Get Hormone Therapy in Drug Form for Breast Cancer
There are 3 classes of drugs used for hormone therapy.
Each works a little differently and causes different side effects.
Using Selective Estrogen Receptor Modulators (SERMs) for Breast Cancer
The SERMs class consists of drugs that keep hormones from binding to their receptors. They do this by mimicking the shape of the hormone and filling the space in the receptor. That leaves the cancer-promoting hormone with no place to bind. There are 3 common SERMs used for breast cancer. You take these as pills.
Using Aromatase Inhibitors for Breast Cancer
If you have not gone through menopause, your ovaries still make most of your estrogen. After menopause, your ovaries no longer make large amounts of estrogen. But your muscles and fat still make some estrogen from male hormones called androgens.
How they work. These drugs interfere with the enzyme aromatase. Its role is to convert androgens, such as testosterone, into estrogen. By affecting how much estrogen is made, aromatase inhibitors deplete the body of estrogen. This helps slow or stop the growth of breast tumors, sometimes even shrinking them. Researchers have found that the drugs cannot lower estrogen levels enough to affect tumor growth in younger women. That’s because their ovaries still make high levels of estrogen. For this reason, these drugs are used only in women who have gone through menopause. Doctors often prescribe them instead of tamoxifen if you’re postmenopausal and your breast cancer has come back.
Common types. These are aromatase inhibitors that the US Food and Drug Administration has approved for breast cancer.
-
Arimedex (anastrozole)
-
Femara (letrozole)
-
Aromasin (exemestane)
Aromatase inhibitors are not all the same. Two major classes of these drugs work in slightly different ways. Type-1 inhibitors include exemestane, which has a lasting effect on estrogen production. Once a woman takes it, she will not be able to make estrogen again. Type-2 inhibitors include anastrozole and letrozole. They work only while you are taking the drug. Once you stop taking the drug, your body can make estrogen again. All 3 drugs are in pill form.
Who they are for. Anastrozole and letrozole are used to treat breast cancer in postmenopausal women who have advanced breast cancer. This means the cancer has spread beyond the breast. It is also called metastatic cancer. You may use these drugs before other hormone therapies. Or you may use it after another hormone therapy, such as tamoxifen, has stopped working. Postmenopausal women can use exemestane if they are no longer benefiting from tamoxifen.
The FDA has approved anastrozole for use after surgery in women with early-stage breast cancer. This extra treatment is called adjuvant therapy. Its purpose is to prevent or delay any remaining cancer cells from growing.
Recently, a study of early-stage breast cancer survivors showed that adding letrozole to the drug regimen reduces the chance that breast cancer will come back. Postmenopausal women who took letrozole after completing 5 years of tamoxifen therapy were less likely to have their cancer return than women not taking letrozole. 1
Researchers are also looking at whether aromatase inhibitors can prevent breast cancer in postmenopausal women who are at high risk. More research is needed to see if these drugs can fill this role.
Using Estrogen-Receptor Downregulators for Breast Cancer
These drugs attack the tumor’s estrogen receptors. They damage the receptors so that they are unable to bind to estrogen. The only drug of this type is Faslodex (fulvestrant) . You get it by a monthly injection into a muscle. Your doctor may prescribe it for you if tamoxifen doesn’t work.
|
Selected References:
1Goss PE, Ingle JN, Martino S, et al. A randomized trial of letrozole in postmenopausal women after five years of tamoxifen therapy for early-stage breast cancer. N Engl J Med. 2003 Nov 6; 349(19): 1793-802.
|