Ibrance Adds 15 Months of Progression-Free Survival in HR+, HER2+ Breast Cancer

Researchers from the Dana-Farber Cancer Institute and international research groups have published data in The New England Journal of Medicine showing that adding the medication Ibrance (palbociclib) to maintenance therapy significantly extends the time patients with double-positive metastatic breast cancer live without their disease progressing.

The phase 3 PATINA trial found that adding Ibrance to the current standard-of-care first-line maintenance therapy resulted in a 15.2-month improvement in progression-free survival, or the time patients lived without their disease spreading or worsening, in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer. The findings, originally presented during a late-breaking oral session at the 47th San Antonio Breast Cancer Symposium in December 2024, address a specific subtype that accounts for approximately 10% of all breast cancers.

Main data that support the findings

The final results of the PATINA study demonstrate that the addition of Ibrance to maintenance anti-HER2 and endocrine therapies led to a significant improvement in progression-free survival compared to standard therapy. Patients treated with the Ibrance combination experienced a median progression-free survival of 44.3 months. In contrast, patients treated with anti-HER2 therapy and endocrine therapy alone experienced a median progression-free survival of 29.1 months.

This extension in median progression-free survival represents an improvement of over 15 months.

At the time of this analysis, which took place at a median follow-up of 53.5 months, the data for overall survival were not yet mature. Principal investigator Dr. Otto Metzger noted in a news release issued by Dana-Farber Cancer Institute that the ability to meaningfully extend the time before disease progression with a well-tolerated regimen offers new hope for individuals living with this challenging subtype of metastatic breast cancer, where the development of resistance to anti-HER2 and endocrine therapy remains a challenge.

Trial details

PATINA was a phase 3, open-label, randomized trial that enrolled patients with HR-positive, HER2-positive metastatic breast cancer. To participate, patients must not have had disease progression after receiving four to eight cycles of initial chemotherapy plus HER2-targeted therapy.

A total of 518 patients underwent randomization, with 261 patients assigned to the Ibrance group to receive maintenance HER2-targeted and endocrine therapies plus Ibrance and 257 patients assigned to the standard-therapy group to receive maintenance HER2-targeted and endocrine therapies alone.

The maintenance anti-HER2 therapy used in the trial included Herceptin or a combination of Herceptin and Perjeta. Ibrance is a selective inhibitor of cyclin-dependent kinases 4 and 6 (CDK 4/6). Preclinical and clinical data suggested that adding this inhibitor might overcome resistance to both endocrine and HER2-directed treatments.

Safety

The safety and tolerability of Ibrance in the PATINA study was consistent with its known profile in HR-positive, HER2-negative metastatic breast cancer, and researchers identified no new safety signals. However, the study did find that the Ibrance group had increased toxic effects compared to the standard-therapy group.

Grade 3 (severe) and 4 (life-threatening) side effects occurred in 79.7% and 10% of patients in the Ibrance group, respectively. In comparison, 30.6% and 3.6% of patients in the standard-therapy group experienced grade 3 and 4 events. The most common adverse events were hematologic toxicities, primarily neutropenia and leukopenia, or low white blood cell counts.

Non-hematologic adverse events included fatigue, stomatitis and diarrhea. These side effects were generally reported as mild to moderate in severity. While the addition of Ibrance led to a higher rate of toxic effects, specifically neutropenia, the regimen was characterized by researchers as well-tolerated for patients with this specific subtype of metastatic breast cancer.

References

1. “Palbociclib for Hormone-Receptor–Positive, HER2-Positive Advanced Breast Cancer” by Dr. Otto Metzger et al., The New England Journal of Medicine.
2. “Addition of CDK 4/6 inhibitor benefits patients with HR+, HER2+ metastatic breast cancer, new study shows,” news release; https://www.dana-farber.org/newsroom/news-releases/2026/addition-of-cdk-46-inhibitor-benefits-patients-with-hr-her2-metastatic-breast-cancer-new-study-shows

Editor's note: This article is for informational purposes only and is not a substitute for professional medical advice, as your own experience will be unique. Use this article to guide discussions with your oncologist. Content was generated with AI and reviewed by a human editor.

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