Abstract
BackgroundCDK4/6 inhibitor in combination with an aromatase inhibitor (AI) as initial endocrine therapy has become standard of care for patients with HR+/HER2– advanced/metastatic breast cancer (mBC). Large representative studies are needed to understand effectiveness of CDK4/6 inhibitor + AI in the real-world clinical setting. This study describes patient characteristics and real-world progression-free survival (rwPFS) in mBC patients treated with Palbociclib + AI in the first line setting. MethodsThe Flatiron longitudinal database contains information from 2 million cancer patients treated in the US from 275 cancer clinics. From this database, 878HR+/HER2– mBC women treated with Palbociclib + AI as first-line therapy between February 2015 and August 2018 with at least 3 months of follow-up available were identified. Patients were followed from start of Palbociclib + AI therapy to November 2018, death, or last visit, whichever came first. rwPFS was defined as months from start of Palbociclib + AI to death or disease progression based on clinical assessment or radiographic progression with or without biopsy confirmation. Kaplan-Meier methods were used to estimate survival proportions in rwPFS. ResultsIn our cohort of 878 eligible patients with a median follow-up of 19.4 months, 66.9% were white, mean age was 65.2 years, 50.8% had visceral disease (liver and/or lung involvement). Among these patients, 92.7% received Letrozole along with Palbociclib. Median rwPFS was 21.9 months (95%CI = 20.1 – 28.2). Table presents median rwPFS by subgroups. ConclusionsThese findings from a large cohort of patients in US routine clinical practices support first-line Palbociclib + AI therapy as standard of care for HR+/HER2- advanced/metastatic breast cancer.Table327P Real-world progression-free survival (rwPFS) by subgroupsTableNMedian rwPFS (months)95%CIAll patients87821.920.1 – 28.2Age, year18-6440721.818.8—26.465-7429421.416.1—29.9≥ 7517728.620.1—NEEthnicityWhite58722.620.3—28.6Black62NE11.3—NEAsian1813.87.8—NEHispanic28NE5.9—NEOther/unknown18319.916.1—NEMenopausal statusPremenopausal (Age≤50)6719.514.3—25.9Postmenopausal (Age>50)81122.420.2—28.7Disease stage at initial diagnosis1 or 231121.917.6—33.1311921.013.1—28.64 (De novo)35922.219.5—32.7Unknown8926.515.5—NEECOG Score032222.418.9—NE1+22521.016.5—28.3No bone-only disease62317.314.6—20.2Bone-only disease255NENEVisceral disease44614.812.7—18.3Nonvisceral disease43233.128.3—NENo# of metastic sites1352NENE226620.217.1—33.03+25611.39.8—13.7NE = not estimable Legal entity responsible for the studyPfizer Inc. FundingPfizer Inc. DisclosureM. Torres: Full / Part-time employment: Emory University; Research grant / Funding (self): Pfizer Inc. X. Liu: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer Inc. J. Mardekian: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer Inc. L. McRoy: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer Inc.
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