Exemestane

Exemestane (brand name Aromasin) belongs to a class of medicines called aromatase inhibitors. Aromatase inhibitors are hormonal therapies used to treat hormone receptor-positive breast cancer.

Exemestane and other aromatase inhibitors lower estrogen levels in the body by blocking an enzyme called aromatase from changing other hormones into estrogen. Lowering estrogen levels can slow or stop the growth of breast cancer cells that rely on estrogen to grow.

Other aromatase inhibitors include anastrozole (Arimidex) and letrozole (Femara).

Who gets exemestane?

Exemestane is FDA-approved to treat hormone receptor-positive breast cancer in postmenopausal women. It can be given:

• To people with early-stage breast cancer after completing 2 to 3 years of tamoxifen to reduce the risk of recurrence
• To people with advanced or metastatic breast cancer that has grown after treatment with tamoxifen

Exemestane can also be used to lower the risk of breast cancer in postmenopausal women who are considered to be at high risk for developing it.

Pre- or perimenopausal women who have hormone receptor-positive breast cancer can take exemestane if the ovaries are stopped from producing estrogen. This is called ovarian suppression, or ovarian shutdown.

Ovarian suppression can be done in two different ways:

• Taking an ovarian-suppression medicine called a gonadotropin-releasing hormone agonist (GnRH agonist). GnRH agonists temporarily put the body into menopause, greatly reducing estrogen.
• Having the ovaries surgically removed (oophorectomy). This procedure causes early menopause that is permanent. Many women choose to take ovarian suppression medicine instead. Talk with your team about what’s best for your situation.

In some cases, men with breast cancer can take exemestane in combination with a GnRH agonist, which stops the body from converting testosterone into estrogen.

How is exemestane given?

Exemestane is a 25 milligram tablet taken daily.

Side effects and things to remember

Like other aromatase inhibitors, exemestane can cause bone loss, sometimes called bone thinning. If you’re at risk of osteoporosis (a condition in which the bones become weak or brittle), or if you already have osteoporosis, your doctor will check your bone density before and during treatment.

Your doctor also will measure Vitamin D levels before starting treatment, as you may need to take a supplement.

If you’re taking another medicine that increases the activity of an enzyme called CYP3A4 (called CYP3A4 inducers), you may need to take a higher dose of exemestane. Examples of these medicines include:

• Antibiotics such as rifampicin
• The anti-seizure medicine phenytoin

There are also other CYP3A4 inducers, too. These can cause a drug interaction that lowers the amount of exemestane in your body. It’s important to share all the medicines and supplements you take with your doctor. Your doctor can review them with you and tell you if you’re on a CYP3A4 inducer.

Exemestane can also cause many of the same side effects as other aromatase inhibitors, including:

• Menopausal symptoms such as hot flashes; genitourinary syndrome of menopause, including vaginal dryness and irritation; and loss of interest in sex
• Bone and joint pain, stiffness
• High blood pressure
• Higher cholesterol
• Insomnia and fatigue
• Nausea and vomiting
• Weakness
• Headache
• Loss of appetite
• Weight gain
• Mood changes
• Constipation or diarrhea
• Dry skin
• Hair thinning