Abstract 219P
Background
CDK4/6 inhibitors (CDK4/6i) with endocrine therapy (ET) represent the milestone of first-line therapy in hormone receptor-positive (HR+) HER2-negative (HER2-) metastatic breast cancer (mBC). Aim of our retrospective study was to identify new prognostic factors in this setting.
Methods
All patients (pts) affected by HR+/HER2- mBC referred to our Institutions from February 2017 to August 2023 and treated with CDK4/6i + ET as first-line setting were included.
Results
220 pts were included. Neutropenia occurred in 95.5% of pts, causing 38.2% of dose reduction and 4.1% of discontinuation. Median PFS (mPFS) was 35.2 months (m) (0.4-71.8). 10.0% of pts obtained complete response (CR), 46.8% partial response (PR), 32.7% disease stability (DS) and 10.5% disease progression (DP). At univariate analysis, mPFS was correlated to neutropenia (35.3m if present vs 9.8m if absent, p=0.0103), dose reduction (not reached (NR) if yes vs 26.2m if not, p=0.0002), treatment interruption (2.4m if yes vs 35.3m if not, p=0.0024) and disease response (NR if CR vs 37.1m if PR vs 35.2m if DS vs 4.3m if DP, p<0.0001). Only neutropenia was confirmed at multivariate analysis (p=0.0279). Median OS (mOS) was 4.3 years (y) (0.13-5.97) and was correlated with response (NR if CR vs 4.3y if PR vs 5.3y if DS vs 1.3y if DP) at univariate (p<0.0001) and multivariate (p=0.0445) analysis. Prognostic Nutritional Index (PNI) was prognostic for mPFS (47.3m if high vs 12.5m if low, p<0.0001) and for mOS (p=0.0006). Systemic Inflammation Index (SII) was prognostic for mPFS (47.3m if low vs 24.1m if high, p=0.0135), but not for mOS (p=0.053). mPFS was correlated to Neutrophil to Lymphocyte Ratio (NLR) at baseline (47.3m if low vs 24.1m if high, p=0.0019) and at better response (p=0.0023). mOS was correlated to baseline NLR (5.4y if low vs 3.4y if high, p=0.0173) and better response NLR (p=0.0179). mPFS was correlated to baseline Platelet-to-Lymphocyte Ratio (PLR) (47.3m if low vs 21.5m if high, p=0.0034) and DP PLR (15.8m if high vs 9.5m if low, p=0.0019), the latter confirmed at multivariate analysis (p=0.0166).
Conclusions
Our study confirmed the efficacy of CDK4/6i in HR+ HER2- mBC, pointing out new prognostic factors as neutropenia, PNI, SII, PLR and NLR, of whom little data are present in literature.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.