Ibrance (palbociclib) in maintenance therapy for HR-positive HER2-positive metastatic breast cancer: PATINA trial results

The New England Journal of Medicine published results of the phase III PATINA trial in patients with HR-positive HER2-positive metastatic breast cancer. The trial compared standard maintenance anti-HER2 and endocrine therapy with or without the addition of Ibrance (palbociclib).

Trial results

The trial randomized 518 patients: 261 to the Ibrance (palbociclib) group and 257 to the standard maintenance therapy group. All patients had previously received 4-8 cycles of chemotherapy and HER2-directed therapy without disease progression before randomization.

• Median progression-free survival was 44.3 months in the palbociclib group vs 29.1 months in the standard therapy group
• 25% reduction in risk of progression or death (HR 0.75; p=0.02)
• Grade 3 adverse events occurred in 79.7% of patients on palbociclib vs 30.6% in the standard therapy group
• Grade 4 adverse events occurred in 10.0% vs 3.6% respectively
• The main contributor to increased toxicity was neutropenia

Clinical significance

For HR-positive HER2-positive metastatic breast cancer, the standard first line has long been chemotherapy with dual HER2 blockade, followed by transition to maintenance therapy if there is no progression. PATINA demonstrates that this maintenance phase can be enhanced by adding a CDK4/6 inhibitor.

Now the discussion of first-line treatment does not end with choosing the induction regimen. It is necessary to plan ahead for what the maintenance strategy will be. The maintenance phase is often underestimated, but this is precisely where the duration of disease control can be influenced.

Limitations

This trial does not apply to all patients with metastatic breast cancer. It pertains specifically to the HR-positive HER2-positive subtype and only to cases where there was no disease progression after initial chemotherapy with HER2-directed therapy.

The trial showed a benefit in progression-free survival but does not provide a basis for automatically applying this regimen to other biological subtypes. If the tumor is HR-negative, if the disease progressed on initial treatment, if there are contraindications or serious toxicity concerns, directly applying PATINA data would be an error.

When a second opinion is helpful

• If after initial chemotherapy and HER2-directed treatment it is unclear how to structure the maintenance phase
• If physicians disagree about adding Ibrance (palbociclib)
• If you want to understand the benefit-risk balance, especially given the potential for neutropenia
• If it is important to evaluate not just the immediate next step but the entire first-line treatment strategy

What to prepare for consultation

• Histopathology report
• IHC and HER2 confirmation results
• Hormone receptor status data
• Discharge summaries for chemotherapy and HER2-directed therapy already received
• Most recent CT, MRI, or PET-CT scans
• Complete blood count and biochemistry panel
• List of comorbidities and current medications

Frequently asked questions

Source

NEJM: Palbociclib for Hormone-Receptor-Positive, HER2-Positive Advanced Breast Cancer