Modified cachexia index and survival in metastatic breast cancer patients treated with CDK 4-6 inhibitors

The objective of this study is to evaluate the correlation between survival outcomes and the modified cachexia index (mCXI) in patients with metastatic breast cancer who have been treated with cyclin-dependent kinase (CDK) 4/6 inhibitors.

This study was conducted on patients with metastatic breast cancer who received CDK 4/6 inhibitors (either Palbociclib or Ribociclib) between January 2020 and November 2024.

240 patients were included. A total of 236 patients (98.3%) were female. Median age was 57 (IQR: 48-66 years). The median follow-up period from the initiation of CDK 4/6 inhibitors to the last control was 20 months. One hundred eighty-four patients (76.7%) received ribociclib, while 56 (23.3%) received palbociclib. At diagnosis, 179 patients (74.6%) had metastatic disease. Patients are classified as modified cachexia index-low (mCXI-Low) and mCXI-High according to the receiver operating characteristic (ROC) analysis results for overall survival (OS) prediction [AUC: 0,654 p:<0,001 Cut-off value = 93.5]. Following multivariate analysis, both progression-free survival [HR: 1.50 (95% CI 1.07-2.12), p = 0.02] and overall survival [HR: 3.22 (95% CI 1.90-5.46), p < 0.001] were found to be significantly associated with mCXI.

mCXI is associated with overall survival in metastatic breast cancer patients who are treated with CDK 4-6 inhibitors.