Ribociclib: a valuable addition to treatment options in breast cancer?

Antihormonal treatment is regarded as the prototype of targeted therapy. As early as 1896, George Thomas Beatson proposed surgical oophorectomy for the treatment of patients with locally advanced, inoperable breast cancer.1 While the underlying biological mechanisms were not understood in those days, the identification of steroid hormones2 and eventually the oestrogen receptor (ER)3 led to the successful utilisation of endocrine treatment in breast cancer. Besides the partial ER-antagonist tamoxifen, the therapeutic armamentarium today consists of aromatase inhibitors (AIs) and the pure antioestrogen fulvestrant; medical ovarian-function suppression with GnRH analogues may be added in premenopausal patients, with surgical oophorectomy still being an alternative.In early stage breast cancer, endocrine therapy reduces recurrence rates by 50% and breast cancer mortality by one-third4; in advanced disease, the sequential administration of non-cross-resistant drugs allows for the delay of cytotoxic chemotherapy. Still, in metastatic disease, secondary resistance will gradually develop with cells becoming insensitive to further endocrine intervention. To improve activity of endocrine therapy by …