PATINA Study: Palbociclib Extends Progression-Free Survival in HR+, HER2+ Metastatic Breast Cancer

A Phase 3 study, known as PATINA, has reported that the addition of the CDK4/6 inhibitor palbociclib to standard anti-HER2 and endocrine therapy extended progression-free survival by more than 15 months in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer. The significant findings were published in the New England Journal of Medicine.

Key Findings and Outcomes

The PATINA study is the first large, randomized Phase 3 trial to demonstrate a clinical benefit for CDK4/6 inhibition in this specific subtype of advanced breast cancer.

Patients receiving palbociclib in combination therapy achieved a median progression-free survival (PFS) of 44.3 months. This compared to 29.1 months for patients in the control group who received anti-HER2 and endocrine therapy alone, representing an extension of 15.2 months.

The trial's primary endpoint was investigator-assessed progression-free survival. Data for overall survival, a secondary endpoint, were not yet mature at the time of the analysis.

Patient Population and Treatment Regimen

The study focused on patients with HR+, HER2+ metastatic breast cancer, a subtype that accounts for approximately 10% of all breast cancers. Despite current treatment advancements, challenges remain with resistance to existing anti-HER2 and endocrine therapies.

Participants in the PATINA study were randomized after receiving induction chemotherapy. One group received palbociclib in addition to anti-HER2 therapy (which included trastuzumab or trastuzumab plus pertuzumab) and endocrine therapy. The control group received anti-HER2 therapy and endocrine therapy alone.

Safety and Tolerability Profile

The safety and tolerability of palbociclib observed in the PATINA study were consistent with its known safety profile in HR+, HER2-negative metastatic breast cancer. No new safety signals were identified.

Common adverse events reported included:

• Hematologic toxicities: Such as neutropenia and leukopenia.
• Non-hematologic adverse events: Including fatigue, stomatitis, and diarrhea, which were generally mild to moderate in severity.

Study Scope and Collaboration

The PATINA study enrolled 518 patients from June 2017 through July 2021 across 109 clinical sites located in the U.S., Europe, New Zealand, and Australia.

The study was sponsored by Alliance Foundation Trials, LLC (AFT) in collaboration with several international cancer research groups, including Breast Cancer Trials, Fondazione Michelangelo, GBG Forschungs GmbH, PrECOG, SOLTI, and Unicancer. Funding support for the study was provided by Pfizer Inc. Dr. Otto Metzger served as the Principal Investigator for the PATINA study.

Palbociclib is not currently indicated for HR+, HER2+ advanced breast cancer. However, these findings suggest a potential new maintenance-therapy approach for this patient population.