Abstract 56P
Background
In a series of phase III clinical studies of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) similar efficacy results were reported, but overall survival (OS) benefit was achieved only with the use of ribociclib. Direct comparison of CDKi is warranted to evaluate the difference in their efficacy in various subgroups of patients (pts).
Methods
We conducted a real-world evidence study to compare the outcomes of pts with metastatic hormone receptor positive HER2-negative breast cancer, who received combination of endocrine therapy with palbociclib (palbo) or ribociclib (ribo) as first-line therapy since 2020 to 2023.
Results
A total of 377 pts with median age of 65 years were included, 218 pts received palbo, 159 pts – ribo. Median follow-up time was 24 months. No difference in median progression-free survival (mPFS) in groups of palbo and ribo was observed (30 months versus 26 months, respectively, HR=1.1, 95% CI 0.8-1.5); 2-year PFS rates were 56% and 51% in palbo and ribo groups, respectively. Although median OS in palbo group was 54 months and in ribo group – 39 months, the difference was not statistically significant (HR=1.28, 95%CI 0.87-1.89); 2-year OS rates were 76% and 78% in ribo and palbo groups, respectively. Hepatic metastases (HR 1.8 [1.1-2.8]) and primary endocrine resistance (HR 2.7, 95% CI 1.6-4.4) were negative prognostic factors. The difference in PFS of palbo versus ribo was observed neither in the subgroup of pts with liver metastases (mPFS were 16 months and 20 months, respectively, HR=0.88, 95% CI 0.4-1.9) nor in pts with primary endocrine resistance (mPFS were 9 and 15 months, respectively, HR 1.83, 95% CI 0.7-4.5).
Conclusions
In real-world practice ribo and palbo demonstrate comparable efficacy both in total population and in subgroups with especially poor prognosis.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
E. Tsareva.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.