Side effects of endocrine therapy for breast cancer

Endocrine therapy options are very important in hormone receptor-positive, i.e., estrogen-sensitive, breast cancer. Selective estrogen receptor inhibitors, anti-estrogens, aromatase inhibitors, gestagens, and GnRH agonists are used. Normally, these forms of treatment are meant for long-term use. Therefore, tolerability, toxicity, and safety with acute and chronic side effects are of great importance. Due to the anti-endocrine mechanisms of all these substances, climacteric symptoms as well as antiresorptive effects in bones (increase in the risk of fracture) are the central side effects. Furthermore, undesirable effects specific for the substances are described in this article.