ERBB2 and breast cancer: <h4>Background</h4>We conducted this study to evaluate the impact of serum inflammatory markers and histopathological features on prognosis in metastatic hormone receptor positive breast cancer patients treated with first line CDK4/6i (cyclin-dependent kinase inhibitors).<h4>Objectives</h4>While serum markers are better indicators in triple-negative and HER-2 positive breast cancers, the PFS (progression-free survival) durations of NLR (neutrophil/lymphocyte ratio), PLR (platelet/lymphocyte ratio), and LMR (platelet/lymphocyte ratios) in luminal A-B group patients vary between studies.