Efficacy of Palbociclib plus Letrozole vs Letrozole Alone for HR+/HER2- metastatic Breast Cancer

Efficacy of Palbociclib plus Letrozole vs Letrozole Alone for HR+/HER2- metastatic Breast Cancer

Introduction

Palbociclib is the first-in-class CDK4/6 inhibitor approved for the treatment of hormone receptor–positive (HR+)/human epidermal growth factor receptor–negative (HER2-) metastatic breast cancer (MBC) in combination with an aromatase inhibitor or fulvestrant.

Aim

To examine the effectiveness of first line palbociclib plus letrozole versus letrozole alone on survival outcomes in patients with HR+/HER2- MBC

Patient Profile

Women aged >18 years at MBC diagnosis with HR+/HER2- MBC before or up to 60 days after the metastatic diagnosis date

Methods

• Retrospective observational analysis of electronic health records
• 1430 patients with > 3 months of follow-up received palbociclib plus letrozole or letrozole alone in the first line setting.

Study Outcomes

• Real-world progression-free survival (rwPFS) and overall survival (OS)
• rwPFS was defined as the time in months from the start of palbociclib plus letrozole or letrozole alone therapy to death or disease progression.

Results

• Palbociclib combination treatment was associated with significantly longer median rwPFS compared to letrozole alone

  Figure 1: Real-world progression-free survival with palbociclib combination vs letrozole alone

   

• Median OS was not reached in the palbociclib group and was 43.1 months with letrozole alone (HR, 0.66; P = 0.0002)
• Significant OS benefit was observed with palbociclib plus letrozole versus letrozole alone (hazard ratio, 0.66)
  • The 2-year OS rate was 78.3% in the palbociclib group and 68.0% with letrozole alone
  • The OS benefit was generally consistent across most subgroups

Figure 2: Overall survival analysis

• 42.2% in the palbociclib group and 62.9% in the letrozole group received a second-line regimen with a CDK4/6 inhibitor, and 25.6% and 9.4%, respectively, received second line chemotherapy.

Table 1: Subsequent second-line anticancer treatments in cohorts after sIPTW analysis

CDK4/6 cyclin-dependent kinase 4/6, sIPTW stabilized inverse probability of treatment weighting.

^*Includes patients who continued treatment, died, or were censored in the first-line setting

^† Patients could have received > 1 category of second-line treatment

Conclusion

First-line palbociclib plus letrozole was associated with longer rwPFS and OS than letrozole alone in a heterogeneous population and among various patient subgroups.

Reference

Breast Cancer Research.2021; 23:37