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Palbociclib (IBRANCE) Revs Up Metastatic Breast Cancer in PATINA Results

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Update on the PATINA Phase 3 Study: Palbociclib in ER+/HER2+ Metastatic Breast Cancer

Approximately 20% of breast cancers overexpress HER2, with 50% of these patients also expressing the estrogen receptor. While anti-HER2 therapies have improved survival outcomes, resistance remains a significant challenge. The rationale for using CDK4/6 inhibitors like palbociclib in HER2-positive disease stems from known benefits in ER-positive settings.

The PATINA study, a phase 3 trial, focused on patients with metastatic ER-positive and HER2-positive breast cancer. After initial treatment with standard chemotherapy and trastuzumab (THP), patients were randomized to either continue with anti-HER2 therapy and endocrine therapy alone or add palbociclib to this regimen.

Study Design and Participant Demographics:

  • Patients received 6-8 cycles of THP before randomization.
  • 518 patients were randomized, with stratification based on previous anti-HER2 therapy, response to induction chemotherapy, and type of hormonal therapy used (fulvestrant or aromatase inhibitors).
  • The study, conducted across eight countries from June 2017 to July 2021, had a primary endpoint of progression-free survival (PFS) with a design power of 90% to detect a hazard ratio of 0.66.

Results:

  • The palbociclib arm showed a median PFS of 44.3 months compared to 29.1 months in the control arm, resulting in a hazard ratio of 0.74 (p=0.0074).
  • The benefit was consistent across various subgroups, including those with prior anti-HER2 therapy or different responses to induction chemotherapy.
  • Secondary endpoints like overall response rate and clinical benefit rate also favored the palbociclib group.
  • Overall survival data remains immature, with median survival not reached in the palbociclib arm and 77 months in the control arm at the time of analysis.

Safety and Tolerability:

  • Common adverse events in the palbociclib group included neutropenia, fatigue, and stomatitis, with neutropenia being the most frequent.
  • The incidence of severe adverse events was similar between arms, and treatment discontinuations due to side effects were rare.

Chapters:
0:00 – Background: HER2+ and ER+ Breast Cancer
0:09 – Why CDK4/6 Inhibitors? Scientific Rationale
0:30 – Overview of the Phase 3 Patina Trial Design
1:06 – Patient Population and Baseline Characteristics
1:30 – Key Results: Progression-Free Survival (PFS)
2:20 – Subgroup Analysis and Secondary Objectives
3:00 – Confirmed Overall Response and Clinical Benefit Rate
3:50 – Overall Survival Data (Immature)
4:15 – Toxicity Profile and Safety Signals
5:10 – Clinical Implications and New Standard of Care
5:45 – Future Steps: FDA and Regulatory Plans
6:40 – Conclusion: Delaying Chemotherapy While Maintaining Quality of Life

Clinical Implications:

  • The study supports the use of palbociclib in combination with anti-HER2 and endocrine therapy, offering a significant PFS benefit with a manageable toxicity profile.
  • This regimen could potentially redefine the standard of care for ER+/HER2+ metastatic breast cancer, emphasizing the strategy of delaying chemotherapy to maintain patient quality of life.

Next Steps:

  • Plans are underway to seek FDA approval based on these findings, aiming to make this treatment combination widely available for the appropriate patient population.

Q&A Highlights:

  • The study’s results suggest palbociclib’s specific benefit in this patient group, not necessarily extrapolating to other CDK4/6 inhibitors without further data.
  • The study reinforces the chronic nature of managing ER+/HER2+ breast cancer, advocating for treatments that extend progression-free periods while maintaining patient quality of life.

This update is intended to inform oncologists of the latest clinical trial outcomes and their potential impact on treatment strategies for ER+/HER2+ metastatic breast cancer.

ASCO 2024: Palbociclib, Pembrolizumab, & Endocrine therapy in HR+/HER2- locally advanced or metastatic breast cancer (MBC) – Alexis LeVee, MD – City of Hope

https://aacrjournals.org/cdnews/news/1943/Palbociclib-Dramatically-Increases-PFS-in

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