Information sheet about the adjuvant use of Exemestane (also called Aromasin).


Exemestane given as part of an adjuvant therapy program is usually taken as a pill once a day every day for 2-3 years after a patient has completed 2-3 years of tamoxifen. 


Exemestane is a hormonal therapy. Exemestane works by lowering estrogen levels in your blood and tissues. This is accomplished by exemestane lowering estrogen production in your body. In women with strongly functioning ovaries (who are still premenopausal) exemestane is not strong enough to prevent ovarian estrogen production. Thus the use of exemestane is only recommended in women who are postmenopausal. Because exemestane is a hormonal therapy for most women taking exemestane the side effects are very mild and do not include chemotherapy like side effects of nausea, vomiting, or hair loss.   


Exemestane is generally considered a useful anti-cancer medicine for early breast cancer.  This is because:


1) It is effective in reducing the risk of breast cancer recurrence in postmenopausal women who have had hormone receptor positive breast cancer and who have completed 2-3 years of tamoxifen and were then switched to exemestane.  It is also effective in reducing the risk of getting a second breast cancer. 


2) For most women the side-effects caused by taking exemestane are very mild. 


You should know that:


Although taking Exemestane can cause benefit by decreasing the risk of recurrence of breast cancer, many women who take exemestane have some mild side-effects, a few women may have severe side effects, and a very few women might die as a result of taking exemestane.  


Exemestane has a well established role for the treatment of women with recurrent metastatic breast cancer, and new information supports its use to help prevent breast cancer recurrence for women who have had early breast cancer. This information comes from a clinical trial in which 4742 women participated. These women were postmenopausal. They had originally had an estrogen or progesterone receptor positive breast cancer.  As part of their original breast cancer therapy they had received 2 to 3 years of tamoxifen. These women because they knew that tamoxifen was only about 40% effective in preventing recurrence accepted random assignment either to complete the planned 5 years of tamoxifen or be switched to complete their 5 years of treatment with exemestane.  


The results of this study have been recently published (in March of 2004).  What the data showed was that the exemestane treated women had about a 30% reduction in their risk of recurrence compared to tamoxifen. For the average woman in this study, there was a 13% chance having a breast cancer recurrence in 3 years if she continued on tamoxifen and a 9% chance if she got Exemestane.  This was for the average woman. For women who had more late risk based on their initially having positive nodes, there was more benefit. For women who had less late risk based on having initially no positive nodes, there was less benefit.  Because the trial was reported with 2.5 years of follow-up for the average woman who is participating, and was only recently published we do not yet have information about the long term effectiveness and safety of switching to exemestane after 2-3 years of tamoxifen.  Thus we can not tell you for sure what the long term relative risks and benefits of exemestane are. 


Although the current recommendation is that 2-3 years of exemestane be given, it is possible that a longer or shorter treatment program will be recommended in the future.


You might select exemestane over no further therapy because you hope the early results will hold up and that the long term benefits of exemestane would improve things for you on average, and that the long term safety would be acceptable, but neither can be absolutely guaranteed based on the informative, promising, but still early data that we have. 


Based on the first 2.5 years of data the comparative benefits of taking exemestane for an average woman after breast cancer surgery and completing 2-3 years of tamoxifen are:


Reduced risk of developing recurrent disease. 

Reduced risk of a second new breast cancer in the opposite breast. 


Keep in mind that some problems happen in women whether or not they are taking exemestane or tamoxifen.  Based on the first 2.5 years of the clinical trial data women getting exemestane compared to those getting tamoxifen the percentage of women reporting problems any time during the study were:



The incidence for severe or very severe levels of these problems was rare. No patient reported severe or very severe hot flashes. For diarrhea 0.4 percent (1 woman out of 250 women) of the exemestane treated patients reported at least 1 severe or very severe episode of this problem, while 0.04 percent (1 woman out of 2500) of the patients who received tamoxifen reported this problem at this level of severity. 


Some guidelines recommend that if you take exemestane that you should be screened for signs of osteoporosis and receive medications to help maintain you bones if you are found to have signs of osteoporosis. 


Because exemestane works by lowering your natural production of estrogens, there are good reasons to believe that if you take estrogen supplements, you will not get the benefits of exemestane. Therefore if you are considering taking supplements that have hormonal effects you should inform and discuss whether this is advisable with your health care team. 


You should discuss and obtain additional information from your breast health professional team about the possible risks and benefits for you of taking exemestane.


(1) Coombes RC, Hall E, Gibson LJ, et al.  A Randomized Trial of Exemestane after Two to Three Years of Tamoxifen Therapy in Postmenopausal Women with Primary Breast Cancer. New England Journal of Medicine 350: (11) 1081-1092, 2004.


You may find it useful to consult the excellent patient information that is present on the Internet at


Revised 8/04