Clinical Practice of the Efficiency and Safety of Palbociclib in Patients with Metastatic Breast Cancer

We aimed to examine the effects of palbociclib and neutropenia in patients with metastatic breast cancer(MBC). From December 2017 to December 2019, 18 patients with estrogen receptor(ER)-positive, human epidermal growth factor receptor 2(HER2)-negative MBC were treated with palbociclib for at least 1 cycle. The most common adverse event(AE) was neutropenia, which occurred in 83% of all cases. With cessation and dose reduction, none of the patients had Grade 4 neutropenia. Palbociclib used in the first- or second-line treatment of MBC showed a higher efficacy than when used as the third-line treatment, which was observed as a longer duration to stay on treatment and higher efficacy.