Aromatase Inhibitors - videos
Aromatase inhibitors lower estrogen levels in the body by blocking aromatase, an enzyme that converts other hormones into estrogen. Like tamoxifen, aromatase inhibitors are used to treat metastatic and early breast cancers that are hormone-receptor positive. Examples of aromatase inhibitors include anastrozole (Arimidex), exemestane (Aromasin) and letrozole (Femara). Unlike tamoxifen, they are only used in postmenopausal women.
Postmenopausal women either begin hormone therapy with an aromatase inhibitor or switch to one after two to three years of tamoxifen. Aromatase inhibitors come in a pill form and are taken every day. Large randomized clinical trials have found that aromatase inhibitors offer the same or better treatment benefit compared to tamoxifen in postmenopausal women with hormone receptor-positive breast cancer [41-48].
More time is needed to assess the long-term risks and benefits of aromatase inhibitors. Like tamoxifen, aromatase inhibitors often cause menopausal symptoms such as night sweats and hot flashes. They have lower rates of vaginal bleeding and discharge, blood clotting problems and endometrial cancer compared to tamoxifen [43,45,47 ], but higher rates of joint pain and arthritis symptoms [41]. And, some results suggest aromatase inhibitors may affect heart health, which is an important concern for postmenopausal women [49].
The use of aromatase inhibitors causes a loss of bone mineral density, leading to higher rates of osteoporosis and bone fracture compared to tamoxifen use [43,47,48,50]. You can help prevent bone loss through regular exercise, getting enough calcium and vitamin D and if you smoke, quitting smoking [51]. Certain drugs may also help prevent osteoporosis. A health care provider may prescribe medicines known as bisphosphonates to help maintain bone mineral density while taking aromatase inhibitors. Although mostly a concern for people with metastatic cancer who take higher doses of bisphosphonates, these drugs can have negative side effects. In some cases, bisphosphonates can cause severe bone, joint and/or muscle pain [52]. Any of these symptoms should be reported to a health care provider right away. In rare cases, a serious jaw bone disorder called osteonecrosis may occur. Treating dental infections prior to treatment with bisphosphonates may reduce this risk [29].
There are unanswered questions about which of the aromatase inhibitors offers the most benefit and how long women should take these drugs. At present, there are no data on the benefits or safety of aromatase inhibitor treatment longer than five years. Another question is whether aromatase inhibitors benefit women who were premenopausal when diagnosed with breast cancer, but later became menopausal because of treatment. New and ongoing studies should help answer such questions. Aromatase inhibitors are being studied in the chemoprevention setting as well, but it is too early for these results.
Updated 09/12/09
