Abstract P1-19-01: Palbociclib plus endocrine therapy significantly enhances overall survival of HR+/HER2- metastatic breast cancer patients compared to endocrine therapy alone - A large institutional study

Abstract

Abstract PURPOSE: Cyclin-dependent kinase 4/6 inhibitor (CDKi) therapy combined with endocrinetherapy is considered standard of care for patients with advanced hormone receptor (HR)-positive, HER2-negative breast cancer (BC). The Breast Medical Oncology Database at MDAnderson Cancer Center (MDACC) was analyzed to assess effectiveness of CDKi+palbociclib. PATIENTS AND METHODS: From a total of 5402 advanced HR+ HER2- BC patients referred toMDACC between 1997 and 2020, we identified eligible patients who received palbociclib incombination with first- (n=778) and second-line (n=410) endocrine therapy. We furtheridentified “control” patients who received endocrine therapy alone in the first- (n=2452) andsecond-line (n=1183) setting. We conducted a propensity score matching analysis to balancethe baseline demographic and clinical characteristics between the palbociclib treated andcontrol cohorts to assess the effect of palbociclib treatment on progression-free survival (PFS)and overall survival (OS). Stratified log-rank test was used to assess the effect of palbociclib inthe matched cohorts. RESULTS: For the propensity-matched cohort in the first-line setting (n=708), the palbociclibgroup had significantly longer median PFS (17.4 vs. 11.1 months; p<0.0001) compared tocontrols. Median OS (44.3 vs. 40.2 months; p =1) did not show any survival benefit in the firstline setting. However, in the second-line setting, with 380 propensity-matched cohort, thepalbociclib group had significantly longer PFS (10 vs 5 months, p<0.0001) as well as OS (33 vs 24months; p < 0.022), compared to controls.2. CONCLUSION: In this single center analysis, of a large cohort of metastatic HR+ HER2- BCpatients, palbociclib in combination with endocrine therapy was associated with improved PFSin both first- and second-line settings and OS in the second-line setting compared withendocrine therapy alone cohort.3 Citation Format: Akshara Singareeka Raghavendra, Min Jin Ha, Nicole M. Kettner, Senthil Damodaran, Rachel Layman, Kelly K Hunt, Yu Shen, Debu Tripathy, Khandan Keyomarsi. Palbociclib plus endocrine therapy significantly enhances overall survival of HR+/HER2- metastatic breast cancer patients compared to endocrine therapy alone - A large institutional study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-19-01.