Real-world postprogression outcomes after first-line treatment with ribociclib plus aromatase inhibitor versus aromatase inhibitor alone in patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative metastatic breast cancer in the United States of America.

BACKGROUND

Ribociclib remains the only cyclin-dependent kinase 4/6 inhibitor to consistently demonstrate overall survival (OS) benefits in the metastatic breast cancer (MBC) setting, with statistically significant and clinically meaningful OS results from all three MONALEESA studies in hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER)-negative MBC. However, real-world (RW) data concerning ribociclib are limited, with brief follow-up durations among RW patients restricting comprehensive OS assessments. Hence, real-world progression-free survival 2 (rwPFS2) and real-world chemotherapy-free survival (rwCFS) can serve as reliable postprogression endpoints.

MATERIALS AND

METHODS

This retrospective analysis utilized deidentified electronic health record data from the Flatiron Health Research Database, evaluating female patients with HR-positive/HER2-negative MBC who initiated first-line treatment with ribociclib plus an aromatase inhibitor (AI) (n = 2571) or AI monotherapy (n = 3078) between 1 January 2020 and 31 January 2025. Analyses were adjusted using inverse probability of treatment weighting.

RESULTS

In the overall cohort, risk of rwPFS2 event was 42% lower with ribociclib plus AI versus AI monotherapy [hazard ratio (HR) 0.58, 95% confidence interval (CI) 0.52-0.65]. A consistent 42% reduction in risk of rwPFS2 event was also observed among patients aged ≥65 years (HR 0.58, 95% CI 0.49-0.68). Risk of rwCFS event was 36% lower with ribociclib plus AI versus AI alone in the overall cohort (HR 0.64, 95% CI 0.57-0.72) and 40% lower among patients aged ≥65 years (HR 0.60, 95% CI 0.51-0.71).

CONCLUSIONS

These RW findings align with clinical trial results, reinforcing that ribociclib provides consistent and substantial postprogression survival benefit for patients with HR-positive/HER2-negative MBC, including those aged ≥65 years.