Yara Abdou, MD, discusses findings from the phase 2 MAINTAIN trial in patients with HER2-negative metastatic breast cancer, as well as the clinical implications of these trial results.
Yara Abdou, MD, assistant professor, medicine, Department of Medicine, Division of Oncology, University of North Carolina School of Medicine, discusses findings from the phase 2 MAINTAIN trial (NCT02632045) in patients with HER2-negative metastatic breast cancer, as well as the clinical implications of these trial results.
The MAINTAIN trial evaluated the efficacy of switching endocrine therapy and continuing a CDK4/6 inhibitor in patients with hormone receptor (HR)–positive, HER2-negative metastatic breast cancer whose disease had progressed on prior endocrine therapy and a CDK4/6 inhibitor. Patients enrolled in the trial switched to treatment with either exemestane [Aromasin] or fulvestrant [Faslodex] depending on which previous endocrine therapy they had received. They were then randomly assigned 1:1 to receive either the CDK4/6 inhibitor ribociclib (Kisqali) or placebo. In total, 86.5% and 11.7% of patients had previously received palbociclib and ribociclib, respectively. Patients who were randomly assigned to the ribociclib arm achieved a median progression-free survival (PFS) of 5.29 months (95% CI, 3.02-8.12) vs 2.76 months (95% CI, 2.66-3.25) in the placebo arm (HR, 0.57; 95% CI, 0.39-0.85; P = .006).
The findings from MAINTAIN contrasted those from the phase 2 PACE trial (NCT03147287). In this trial, patients with estrogen receptor–positive, HER2-negative metastatic breast cancer who received palbociclib plus fulvestrant after a prior CDK4/6 inhibitor and endocrine therapy did not experience a significant PFS benefit vs those who received fulvestrant alone. Of those enrolled on the trial, 90% of patients had received prior palbociclib and 4.5%, 4.1%, and 1.4% of patients had received prior ribociclib, abemaciclib (Verzenio), and palbociclib/ribociclib, respectively.
Contrasting findings between MAINTAIN and PACE indicate that switching CDK4/6 inhibitors post-progression may be the most effective treatment approach for patients with HR-positive, HER2-negative metastatic breast cancer who progressed on an initial CDK4/6 inhibitor, Abdou says. Differences between CDK4/6 inhibitors may also contribute to the data discrepancies that favor ribociclib over palbociclib in this setting, Abdou concludes.