Ribociclib plus fulvestrant has produced the longest median overall survival (OS) observed to date in patients with treatment-naïve advanced breast cancer enrolled in a phase 3 trial, according to researchers.
The median OS with the combination was 67.6 months, according to updated data from the MONALEESA-3 trial. The data also showed that ribociclib plus fulvestrant prolonged OS by 15.8 months, when compared with fulvestrant plus placebo.
These results were presented at ESMO Breast Cancer 2022 by Patrick Neven, MD, PhD, of UZ Leuven in Belgium.
The phase 3 MONALEESA-3 trial (ClinicalTrials.gov Identifier: NCT02422615) was designed to compare ribociclib-fulvestrant with fulvestrant-placebo in treatment-naïve or endocrine-resistant postmenopausal patients with HR-positive, HER2-negative advanced breast cancer.
The current analysis includes only the 365 patients who were treatment-naïve for advanced breast cancer at baseline. In this group, 237 patients received ribociclib plus fulvestrant and 128 received placebo plus fulvestrant.
The median follow-up was 70.8 months. The median OS was 67.6 months with ribociclib and 51.8 months with placebo (hazard ratio [HR], 0.67; 95% CI, 0.50-0.90). The 5-year OS rate was 56.5% and 42.1%, respectively.
There was a significant improvement in second progression-free survival (PFS2) with ribociclib. The median PFS2 was 50.7 months with ribociclib and 34.6 months with placebo (HR, 0.64; 95% CI, 0.49-0.84).
The median chemotherapy-free survival was longer with ribociclib as well. It was 49.2 months with ribociclib and 29.0 months with placebo (HR, 0.62; 95% CI, 0.48-0.81).
Most patients discontinued study treatment — 198 in the ribociclib arm and 117 in the placebo arm. In this group, 81.8% of patients in the ribociclib arm and 89.7% of those in the placebo arm received subsequent antineoplastic therapy. Use of CDK4/6 inhibitors was higher in the placebo arm (35.0%) than in the ribociclib arm (16.7%).
Dr Neven noted that no new safety signals were observed with first-line ribociclib, and the frequency of adverse events (AEs) was generally consistent with prior analyses.
Any-grade AEs of special interest (in the ribociclib and placebo arms, respectively) included neutropenia (73.8% vs 4.7%), leukopenia (32.5% vs 1.6%), hepatobiliary toxicity (26.6% vs 17.2%), prolonged QT interval (10.5% vs 0.8%), and interstitial lung disease/pneumonitis (3.4% vs 0.8%).
Disclosures: This research was supported by Novartis Pharmaceuticals Corporation. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.
Neven P, Fasching PA, Chia S, et al. Updated overall survival (OS) results from the firstline (1L) population in the Phase III MONALEESA-3 trial of postmenopausal patients (pts) with HR+/HER2- Advanced breast cancer (ABC) treated with ribociclib (RIB) + fulvestrant (FUL). ESMO Breast Cancer 2022; May 3-5, 2022. Abstract LBA4.