How does exemestane compare to tamoxifen and raloxifene?

Historically, tamoxifen was found to be effective in preventing breast cancer because women who took it for treatment of cancer in one breast were found to have a significantly reduced risk of developing cancer in the opposite breast. Doctors know that taking tamoxifen before menopause, earlier in life, has a long-term protective effect, and that tamoxifen and raloxifene are effective in preventing breast cancer in both pre- and postmenopausal women. Exemestane, on the other hand, is effective only after menopause. It can't be used to protect women during the important years before menopause, but only in their later years.

The research so far indicates that exemestane appears to be safer than tamoxifen and raloxifene, which are associated with a higher risk of endometrial cancer and blood clots, as well as effects such as fatigue and depression. Because of these risks and effects, many women are reluctant to take tamoxifen and raloxifene. Although bone loss has been a concern with other aromatase inhibitors, exemestane did not produce any measurable changes in bone health. Its main side effects included aches, hot flashes, joint pain, and fatigue—but overall these effects were less problematic than those associated with tamoxifen. So overall, exemestane's safety profile appears to be very reassuring.