Palbociclib in advanced stage hormone receptor-positive breast cancer: real-world data from a Chilean multicentre registry

Background: The addition of cyclin-dependent kinases inhibitors (CDKi) to endocrine therapy (ET) as the first-or second line treatment improves progression-free and overall survival (OS) in hormone receptor-positive, HER2 negative (HR+/HER2-) advanced stage breast cancer (ABC). Our study compared survival rates and prognostic factors in Chilean patients that used palbociclib as first or subsequent (>= second) lines of treatment in a real-world setting.Methods: Our retrospective population-cohort study included HR+/HER2-ABC patients. We calculated 5-year OS and performed a multivariate analysis to determine prognostic factors.Results: A total of 106 patients were included. Median age was 49 years (19-86), 28.3% (30) had de novo stage IV disease; 63% received palbociclib with ET as first line, 54% of them with aromatase inhibitor over fulvestrant. Median OS for the entire cohort was 99 months and 5-year OS was 69%. Patients that received first line palbociclib had a 5-year OS of 89% versus 43% for ET monotherapy or >= second line palbociclib (p = 0.0062). Multivariate analysis showed that the year at diagnosis and CDKi timing (first line versus >= second line) were significantly associated with OS.Conclusion: Our real-world data show that first-line CDKi + ET provides a statistically significant benefit in OS versus >= second line in HR+/HER2-ABC patients.