Prognostic and Predictive Factors in Metastatic Breast Cancer Patients Treated with CDK4/6 Inhibitors

To evaluate the safety and efficacy of CDK4/6 inhibitors in combination with hormone therapy, and to investigate potential predictive markers of treatment in metastatic breast cancer (MBC).

An observational study. Place and Duration of the Study: Department of Medical Oncology, Faculty of Medicine, Eskisehir Osmangazi University, Eskisehir, Turkiye, from January 2019 to December 2023.

Eighty patients with HR+ HER2- MBC treated with CDK4/6 inhibitors were inducted. Mean overall survival (OS) and progression-free survival (PFS) were compared using t-tests or ANOVA, while Pearson's correlation was used to assess relationships between continuous variables and survival. Kaplan-Meier and Cox regression analyses were performed to analyse variables affecting PFS and OS and to determine treatment response to risk factors.

Ribociclib was used in 70 patients, and palbociclib in 10 patients. A significant difference in PFS was observed between the CDK4/6 inhibitor agents (p = 0.034), with a longer mean PFS in the palbociclib group. A weak negative correlation was found between NLR and PFS (r = -0.289, p = 0.010). The number of involved lymph nodes showed a weak positive correlation with OS (r = 0.327, p = 0.040). Time to metastasis and treatment duration contributed significantly to OS as an independent variable (p = 0.001 and p = 0.003), and the CDK4/6 agent contributed significantly to PFS as an independent variable (p = 0.008). There was no statistically significant change in OS with the preferred CDK4/6 agent.

There is a significant difference in the use of CDK4/6, which may supplement standard hormone therapy in the treatment of HR+ HER2- MBC patients.

CDK4/6 inhibitors, Breast cancer, Neutrophil-to-lymphocyte ratio.