Abstract 3536
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
| N | Median rwPFS (months) | 95%CI | |
|---|---|---|---|
| All patients | 878 | 21.9 | 20.1 – 28.2 |
| Age, year | |||
| 18-64 | 407 | 21.8 | 18.8—26.4 |
| 65-74 | 294 | 21.4 | 16.1—29.9 |
| ≥ 75 | 177 | 28.6 | 20.1—NE |
| Ethnicity | |||
| White | 587 | 22.6 | 20.3—28.6 |
| Black | 62 | NE | 11.3—NE |
| Asian | 18 | 13.8 | 7.8—NE |
| Hispanic | 28 | NE | 5.9—NE |
| Other/unknown | 183 | 19.9 | 16.1—NE |
| Menopausal status | |||
| Premenopausal (Age≤50) | 67 | 19.5 | 14.3—25.9 |
| Postmenopausal (Age>50) | 811 | 22.4 | 20.2—28.7 |
| Disease stage at initial diagnosis | |||
| 1 or 2 | 311 | 21.9 | 17.6—33.1 |
| 3 | 119 | 21.0 | 13.1—28.6 |
| 4 (De novo) | 359 | 22.2 | 19.5—32.7 |
| Unknown | 89 | 26.5 | 15.5—NE |
| ECOG Score | |||
| 0 | 322 | 22.4 | 18.9—NE |
| 1+ | 225 | 21.0 | 16.5—28.3 |
| No bone-only disease | 623 | 17.3 | 14.6—20.2 |
| Bone-only disease | 255 | NE | NE |
| Visceral disease | 446 | 14.8 | 12.7—18.3 |
| Nonvisceral disease | 432 | 33.1 | 28.3—NE |
| No# of metastic sites | |||
| 1 | 352 | NE | NE |
| 2 | 266 | 20.2 | 17.1—33.0 |
| 3+ | 256 | 11.3 | 9.8—13.7 |
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.
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