Abstract PS02-01: Efficacy, safety, and quality of life with ribociclib + endocrine therapy in elderly patients with HR+/HER2– advanced breast cancer across the MONALEESA-2, -3, and -7 trials

Abstract Background: Ribociclib (RIB) + endocrine therapy (ET) showed statistically significant progression-free survival (PFS) and overall survival (OS) benefits in MONALEESA-2, -3, and -7 in patients (pts) with HR+/HER2− advanced breast cancer (ABC). Here, we report efficacy, safety, and quality of life (QOL) with RIB + ET in elderly pts in the MONALEESA trials. Methods: Data were pooled from the MONALEESA-2, -3, and -7 trials of pre- and postmenopausal pts with HR+/HER2− ABC treated with first-line RIB + ET or placebo (PBO) + ET. The tamoxifen cohort in MONALEESA-7 and pts with early relapse were excluded from this analysis. PFS, OS, and time to first chemotherapy (TTC) were analyzed in pts <65 y, 65- <75 y, and ≥75 y using Kaplan-Meier methods. Time to definitive deterioration (TTD) by ≥10 points in global health status (GHS) was analyzed across age subgroups using Kaplan-Meier methods. Results: Of the 1229 pts included in this analysis, 773 (62.9%) were <65 y, 335 (27.3%) were 65- <75 y, and 121 (9.8%) were ≥75 y. There were minor differences in baseline characteristics between the age groups: slightly higher % of pts in the ≥75 y group with a ECOG status of 1 and slightly higher % of de novo disease in the <65 y group (Table). Regardless of age, a PFS and OS benefit was seen with RIB + ET vs PBO + ET (Table). RIB + ET also delayed the median TTC in all age groups. In the RIB + ET group, the most common first subsequent antineoplastic treatment was hormonal therapy alone ( <65 y, 26.3%; 65- <75 y, 41.6%; ≥75 y, 38.1%). In the ≥75 y subgroup, pts in the RIB + ET arm (6.3%) less frequently used chemotherapy alone as the first subsequent antineoplastic treatment vs the PBO + ET (24.5%) arm. In pts <65 y, safety results were consistent with those in the overall trial population. In pts 65- <75 y and ≥75 y, the most common any grade adverse events (AEs) with RIB + ET vs PBO + ET were neutropenia (67.6% vs 5.4% and 52.9% vs 3.8%), nausea (52.7% vs 32.0% and 52.9% vs 40.4%), fatigue (42.0% vs 38.1% and 36.8% vs 21.2%), and diarrhea (39.9% vs 30.6% and 48.5% vs 32.7%). For RIB + ET vs PBO + ET, rates of grade 3/4 febrile neutropenia ( <65 y, 1.2% vs 0.3%; 65- <75 y, 1.1% vs 0; ≥75 y, 2.9% vs 0), all grade interstitial lung disease ( <65 y, 1.0% vs 0.6%; 65- <75 y, 2.7% vs 0.7%; ≥75 y, 7.4% vs 0), and all grade QT prolongation ( <65 y, 9.1% vs 2.9%; 65- <75 y, 11.2% vs 4.1%; ≥75 y, 16.2% vs 1.9%) were numerically higher in pts 65- <75 y and ≥75 y than in pts <65 y. Rates of discontinuation due to AEs with RIB + ET vs PBO + ET were 14.6% vs 3.1% in pts <65 y, 19.7% vs 6.8% in pts 65- <75 y, and 41.2% vs 7.7% in pts ≥75 y. In pts who discontinued treatment due to AEs, the percentage of pts without prior dose reduction was 34.4% in pts <65 y, 40.5% in pts 65- <75 y, and 50.0% in pts ≥75 y. TTD in GHS was prolonged with RIB + ET vs PBO + ET in pts <65 y. In pts 65- <75 y and ≥75 y, TTD was generally similar with RIB + ET vs PBO + ET (Table). Conclusions: This pooled analysis of the MONALEESA-2, -3, and -7 trials demonstrated PFS and OS benefits with RIB + ET in elderly pts consistent with those observed in younger pts. Across age subgroups, treatment with RIB + ET also delayed TTC. Overall, RIB was well tolerated in elderly pts, with a safety profile consistent with what is anticipated for an older patient population. Additionally, there was no difference in TTD in GHS with RIB + ET vs PBO + ET in pts 65- <75 y and pts ≥75 y. Citation Format: Lowell Hart, Seock-Ah Im, Sara Tolaney, Mario Campone, Timothy Pluard, Berta Sousa, Gilles Freyer, Thomas Decker, Kevin Kalinsky, Astrid Thuerigen, Melissa Gao, Huilin Hu, Sherko Küemmel. Efficacy, safety, and quality of life with ribociclib + endocrine therapy in elderly patients with HR+/HER2– advanced breast cancer across the MONALEESA-2, -3, and -7 trials [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS02-01.