Letrozole

Letrozole is approved to treat postmenopausal women with certain forms of breast cancer. Among the types of breast cancer that can be treated with this medicine are early breast cancer that is hormone receptor-positive and advanced breast cancer that is either hormone receptor-positive or for which the hormone receptor is unknown. Letrozole is generally taken once a day as a tablet. Side effects of letrozole can include hot flashes, weakness, and joint pain.

 

What Is Letrozole?

Letrozole (Femara®) is a prescription medication used to treat breast cancer in postmenopausal women. Specifically, the drug has been licensed to treat postmenopausal women who:
 
  • Have early breast cancer that is hormone receptor-positive and who have had surgery
     
  • Have taken tamoxifen (Nolvadex®, Soltamox™) for five years after surgery or radiation therapy for breast cancer
     
  • Have advanced or metastatic (spreading) breast cancer that is either hormone receptor-positive or hormone receptor-unknown.
     
(Click What Is Letrozole Used For? for more information on what the drug is used for, including possible off-label uses.)
 

Who Makes Letrozole?

Letrozole is made by Novartis Pharmaceuticals.
 

How Does Letrozole Work?

Letrozole is part of a group of medications called aromatase inhibitors. Aromatase is an enzyme found in various places in the body. These enzymes help produce estrogens (in particular, a certain estrogen called estradiol). In postmenopausal women, most of the estrogen in the body is made by aromatase. By blocking these enzymes, letrozole helps to decrease the amount of estrogen in the body.
 
Many breast cancers are sensitive to the estrogen hormone, meaning that the tumor grows with its help. When a tumor is sensitive to estrogen, it has receptors on the outer surface of its cells, into which estrogen fits like a key opening a lock. When this connection is made, the cancer grows. Breast cancers that have estrogen (and/or progesterone) receptors are known as hormone receptor-positive tumors.
 
By decreasing estrogen production, letrozole can help decrease the growth of these breast cancers. This type of breast cancer treatment is known as hormonal therapy (see Breast Cancer Hormone Treatment).
 
(Letrozole Continued: Page 2)
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Written by/reviewed by: Kristi Monson, PharmD; Arthur Schoenstadt, MD
Last reviewed by: Kristi Monson, PharmD;