Ribociclib and Palbociclib Are Safe and Effective for Treating Metastatic Breast Cancer: A Retrospective Study

Area of Science:

• Oncology
• Pharmacology
• Clinical Trials

Background:

• Cyclin-dependent kinase (CDK) 4/6 inhibitors are standard first-line treatments for hormone receptor-positive metastatic breast cancer when combined with endocrine therapy.
• Limited comparative data exists for first-line CDK 4/6 inhibitor treatments in real-world settings.

Purpose of the Study:

• To compare the efficacy and safety of ribociclib and palbociclib as first-line treatments for metastatic hormone receptor-positive breast cancer in real-world clinical practice.
• To evaluate the impact of dose reductions on treatment outcomes in Asian populations.

Main Methods:

• Retrospective observational study at two tertiary medical centers.
• Inclusion of patients receiving either palbociclib or ribociclib with endocrine therapy.
• Assessment of treatment response using RECIST 1.1 criteria, with 24-month progression-free survival (PFS) as the primary endpoint. Safety outcomes were also compared.

Main Results:

• Comparable 24-month PFS rates between ribociclib and palbociclib cohorts (55.4% vs. 55.2%, HR=1.110, p=0.736).
• Significantly higher objective response rate in the palbociclib group (43.2%) compared to the ribociclib group (30.2%, p=0.035).
• High rates of dose reduction due to toxicity in both groups (41.2% for palbociclib, 47.2% for ribociclib); comparable adverse event profiles, with slightly more grade 1 fatigue in the ribociclib group.

Conclusions:

• Ribociclib and palbociclib demonstrate similar 24-month efficacy in Taiwanese real-world practice for metastatic hormone receptor-positive breast cancer.
• Dose reductions do not compromise the efficacy of these targeted therapies.
• Proactive, toxicity-guided dose adjustments can optimize patient tolerability without sacrificing oncological outcomes in Asian populations.