The addition of a CDK 4/6 inhibitor to standard therapy in patients with "double-positive" metastatic breast cancer significantly extended the time the disease did not progress according to new data presented today at the San Antonio Breast Cancer Symposium. The results of the phase 3 PATINA trial presented by Otto Metzger, M.D., medical oncologist at Dana-Farber Cancer Institute and principal investigator of the trial for Alliance Foundation Trials, demonstrated that adding palbociclib to the current standard-of-care first-line maintenance therapy resulted in a more than 15 month improvement in progression-free survival in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer.
Approximately 10% of all breast cancers are HR+, HER2+, which is sometimes referred to as double-positive or triple-positive breast cancer. Despite advances in treatment, the development of resistance to anti-HER2 and endocrine therapy is a challenge, and novel therapeutic approaches are needed for HR+, HER2+ metastatic breast cancer.
In the PATINA study, participants with metastatic disease who were previously treated with anti-HER2 therapy were randomized to receive palbociclib, in addition to anti-HER2 therapy and endocrine therapy, or anti-HER2 therapy and endocrine therapy alone. The primary endpoint was progression-free survival as assessed by the investigator. The median progression free survival was 44.3 months for patients treated with palbociclib in combination with anti-HER2 therapy (trastuzumab or trastuzumab plus pertuzumab) and endocrine therapy, and 29.1 months for patients treated with anti-HER2 therapy and endocrine therapy alone, representing an extension in median PFS of over 15 months. Overall survival, a secondary endpoint, was not yet mature at the time of the analysis.
"PATINA is the first large Phase 3 study to show the benefit of CDK4/6 inhibition in HR-positive, HER2-positive metastatic breast cancer," said Metzger. "These results support the potential of this maintenance treatment to slow disease progression and improve clinical outcomes in this patient population."
The safety and tolerability of palbociclib in the PATINA study was consistent with its known safety profile in HR+, human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer, and no new safety signals were identified. The most common adverse events observed were hematologic toxicities, such as neutropenia and leukopenia. Non-hematologic adverse events included fatigue, stomatitis and diarrhea, which were generally mild to moderate in severity.
PATINA is sponsored by Alliance Foundation Trials, LLC (AFT) in collaboration with six international cancer research groups in the U.S., France, Germany, Italy, Spain, Australia, and New Zealand. Funding support was provided by Pfizer.
