We sought to compare the rates of SN and FN from clinical trials to real-world experience, correlate factors with SN and FN, and quantify granulocyte colony-stimulating factor (G-CSF) use in HER2-negative (HER2-) metastatic breast cancer (mBC).<h4>Methods</h4>We performed a retrospective analysis of patients treated with SG for advanced HER2- BC at a single US institution with a diverse patient population. Here, CSF3 is linked to breast cancer.