4401 - Real-world effectiveness of first-line palbociclib + letrozole for metastatic breast cancer 4 years post approval in the US

Background

In Feb 2015, palbociclib plus letrozole (P+L) became the first cyclin-dependent-kinase 4/6 inhibitor approved for mBC/aBC in the US. Until now, long-term outcomes studies have included a limited number of patients receiving P+L. The objective of this study is to describe real-world patient characteristics and clinical effectiveness associated with P+L as initial endocrine-based therapy use 4 years post approval.

Methods

Adult postmenopausal women diagnosed with metastatic HR+/HER2- breast cancer who initiated P+L as first-line therapy on or after 2/3/2015 were identified by providers in the Cardinal Health Oncology Provider Extended Network, including 1800 oncologists/hematologists in the US. A subset of providers abstracted data related to patient characteristics and clinical outcomes including disease response and disease progression into an electronic case report from (eCRF). Data were abstracted from the time of initiation of P+L through Feb 2019 (or end of follow up/death). Providers were shown response classification schema corresponding to RECIST v1.1 and asked to indicate the patient’s best response if recorded. The objective response rates (ORR – incl. complete response [CR] and partial response [PR]), clinical benefit rates (CBR – incl. CR+PR+stable disease [SD] >24 wks), and progression-free survival (PFS) rate at 12-month were reported. Each eCRF was reviewed by independent clinical staff; source data was verified on 10% of the patients.

Results

31 providers submitted 202 eCRFs, of which, 193 were eligible. Median follow-up from 1L P+L initiation was 15.4 months, 45.6% of patients had discontinued P+L at data cut-off. Table shows key patient characteristics and ORR, CBR, and PFS rate at 12-month, each showing benefit of 1L P+L in the real-world.Table:

338P

^†Excluding 43 patients with duration of treatment <24 wks

Conclusions

These real-world data demonstrate the benefit of 1L P+L 4 years post approval in the US and support the clinical benefit of 1L P+L reported in randomized clinical trials.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Pfizer Inc.

Funding

Pfizer Inc.

Disclosure

J. Kish: Full / Part-time employment: Cardinal Health; Advisory / Consultancy, Paid consultant in connection with the development of this abstract: Pfizer Inc. J. Trocio: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer Inc. T. Miller: Full / Part-time employment: Cardinal Health; Advisory / Consultancy, Paid consultant in connection with the development of this abstract: Pfizer Inc. D. Nero: Full / Part-time employment: Cardinal Health; Advisory / Consultancy, Paid consultant in connection with the development of this abstract: Pfizer Inc. D. Liassou: Full / Part-time employment: Cardinal Health; Advisory / Consultancy, Paid consultant in connection with the development of this abstract: Pfizer Inc. X. Liu: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer Inc. L. McRoy: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer Inc. B. Feinberg: Full / Part-time employment: Cardinal Health; Advisory / Consultancy, Paid consultant in connection with the development of this abstract: Pfizer Inc.