3536 - Palbociclib plus an aromatase inhibitor as first-line therapy for metastatic breast cancer in US clinical practices: Real-world progression-free survival analysis

Background

CDK4/6 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.

Methods

The Flatiron longitudinal database contains information from 2 million cancer patients treated in the US from 275 cancer clinics. From this database, 878 HR+/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.

Results

In 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.Table:

327P Real-world progression-free survival (rwPFS) by subgroups

NE = not estimable

Conclusions

These 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.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Pfizer Inc.

Funding

Pfizer Inc.

Disclosure

M. 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.