Safety profiles of aromatase inhibitors and selective estrogen-receptor modulators in the treatment of early breast cancer.

For the medical treatment of early breast cancer, aromatase inhibitors (AIs) such as anastrozole, letrozole, and exemestane are more effective than selective estrogen-receptor modulators (SERMs) such as tamoxifen (TAM). However, the adverse events associated with AIs are different from those associated with SERMs. Hot flushes, gynecological disorders, and thrombosis are more frequent in patients treated with TAM than in those treated with AIs. Conversely, osteoporosis, fractures, joint symptoms, and myalgia are more common in patients receiving AIs. Osteoporosis and bone fractures resulting from osteoporosis are important issues for patients treated with AIs. The precise management of bone health, in strict accordance with clinical guidelines, is vital in patients receiving AIs. AI-related joint symptoms are also one of the most important considerations for patients taking AIs. AI-related joint symptoms are the most common reason for the discontinuation of AIs. Confirmed management strategies for AI-related joint symptoms are unavailable at present. In patients receiving AIs, long-term adverse events (for example, those occurring as a result of changing lipid metabolism) remain unclear. There is a clear need to elucidate AI-related adverse events over the long term and to establish management strategies for AI-related adverse events, such that AIs can be used safely in patients with breast cancer over long periods of time.