Abstract 3599
Background
Palbociclib, the first clinically available oral CDK4/6 inhibitor, in combination with endocrine therapy has become standard of care for HR+/HER2- advanced/metastatic breast cancer (MBC). No real-world studies have examined relative effectiveness of palbociclib plus endocrine therapy compared with endocrine therapy alone. This study compared real-world progression free survival (rwPFS) of palbociclib plus letrozole (PB+LE) vs letrozole alone (LE) for MBC in US routine clinical practices.
Methods
We conducted a retrospective analysis of MBC patients from the Flatiron Health longitudinal database, which contains electronic health records from 275 cancer clinics representing more than 2 million actively treated cancer patients in the US. Between February 2015 and August 2018, 1416 HR+/HER2– MBC women started PB+LE (n = 798) or LE (n = 618) as first-line therapy. Patients were evaluated from start of PB+LE or LE to November 2018, death, or last visit, whichever came first. rwPFS was defined as months from start of PB+LE or LE to death or disease progression based on clinical assessment or evidence by radiographic scan/tissue biopsy. 1:1 propensity score (PS) matching was used to balance patient characteristics.
Results
Of 1416 eligible patients, 906 were 1:1 PS matched (453 for each cohort). Median follow-up was 16.8 months, median age was 68.0 years, 70% were white, and 49.7% had visceral disease. Median rwPFS was 24.5 months (95%CI = 20.7 – 32.7) in PB+LE cohort and 17.1 months (95%CI=13.7—19.8) in LE cohort (HR = 0.68, 95%CI=0.56—0.84, p =.0003). Table presents key patient characteristics and landmark rwPFS rates.Table:
329P Patient characteristics and real-world progressionfree survival (rwPFS)
Variable | PB+LE (N = 453) | LE alone (N = 453) |
---|---|---|
Median age (years) | 68.0 | 68.0 |
White (%) | 69.8 | 70.6 |
Median number of metastatic sites (n) | 2.0 | 2.0 |
Bone only disease (%) | 26.9 | 32.2 |
Visceral disease (%) | 49.7 | 49.7 |
Median rwPFS, months (95%CI) | 24.5 (20.7—32.7) | 17.1 (13.7—19.8) |
rwPFS rate at 6 months (%) | 82.8 | 74.5 |
rwPFS rate at 12 months (%) | 72.1 | 58.9 |
rwPFS rate at 18 months (%) | 60.1 | 48.4 |
rwPFS rate at 24 months (%) | 50.2 | 39.1 |
Median follow-up, months (IQR) | 16.8(8.1—27.1) | 16.8(6.9—26.9) |
PB+LE = Palbociclib plus letrozole; LE = Letrozole alone; IQR = Interquartile Range
Conclusions
The first comparative analysis of a CDK4/6 inhibitor in combination with endocrine therapy compared to endocrine therapy alone provides real-world evidence confirming the findings of PFS benefit demonstrated in clinical trial data for palbociclib in diverse clinical practices.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Pfizer Inc.
Funding
Pfizer Inc.
Disclosure
R.M. Layman: Research grant / Funding (institution): 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.
Resources from the same session
4401 - Real-world effectiveness of first-line palbociclib + letrozole for metastatic breast cancer 4 years post approval in the US
Presenter: Jonathan Kish
Session: Poster Display session 2
Resources:
Abstract
5876 - Palbociclib-Fulvestrant (PALBO-FUL) and Everolimus -Exemestane (EVE-EXE) for Second line Hormonal Treatment (HT) of Metastatic Breast Cancer (MBC) with Lobular Histology: a Propensity Score Matched Analysis of a Multicenter ‘Real-World’ Patients (pts) Series.
Presenter: Armando Orlandi
Session: Poster Display session 2
Resources:
Abstract
3587 - Dose-escalation study of G1T48, an oral selective estrogen receptor degrader (SERD), in postmenopausal women with ER+/HER2- locally advanced or metastatic breast cancer (ABC)
Presenter: E Dees
Session: Poster Display session 2
Resources:
Abstract
5696 - Final results of the STEM trial: SFX-01 in the Treatment and Evaluation of ER+ Her2- Metastatic breast cancer (mBC)
Presenter: Sacha Howell
Session: Poster Display session 2
Resources:
Abstract
1475 - Alpelisib (ALP) + Fulvestrant (FUL) in Hormone-Receptor Positive (HR+), Human Epidermal Growth Factor Receptor-2–Negative (HER2–) Advanced Breast Cancer (ABC): Subgroup Analysis by Presence of Visceral Metastasis (VM) in the SOLAR-1 Trial
Presenter: Mario Campone
Session: Poster Display session 2
Resources:
Abstract
2549 - Phase 1 Dose Escalation Study of a Selective Androgen Receptor Modulator RAD140 in Estrogen Receptor Positive (ER+), HER2 Negative (HER2-) Breast Cancer (BC)
Presenter: Erika Hamilton
Session: Poster Display session 2
Resources:
Abstract
3787 - A Phase I study of XZP-3287, a novel oral CDK4/6 Inhibitor, administered on a continuous dosing schedule, in patients with advanced solid tumours
Presenter: Binghe Xu
Session: Poster Display session 2
Resources:
Abstract
4835 - Phase-I dose-escalation and expansion study of the PARP inhibitor, fluzoparib (SHR3162), in patients with advanced solid tumors
Presenter: Huiping Li
Session: Poster Display session 2
Resources:
Abstract
5083 - Phase 2 study of DHP107 (Liporaxel®, oral paclitaxel) in first-line, HER2 negative recurrent/metastatic breast cancer (OPTIMAL study, NCT03315364)
Presenter: Jin-Hee Ahn
Session: Poster Display session 2
Resources:
Abstract
2674 - Multicenter Phase I Trial of Trastuzumab Emtansine (T-DM1) in Combination with Non-Pegylated Liposomal Doxorubicin (NPLD) in HER2[+] Metastatic Breast Cancer (MBC). THELMA Study
Presenter: Elena López-Miranda
Session: Poster Display session 2
Resources:
Abstract