Final Results of RIGHT Choice: Ribociclib Plus Endocrine Therapy Versus Combination Chemotherapy in Premenopausal Women With Clinically Aggressive Hormone Receptor-Positive/Human Epidermal Growth Factor Receptor 2-Negative Advanced Breast Cancer

Abstract

Purpose: A head-to-head comparison of efficacy between a cyclin-dependent kinase 4/6 inhibitor plus endocrine therapy (ET) versus combination chemotherapy (CT) has never been reported in patients with clinically aggressive hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (ABC).

Methods: In this open-label, multicenter, randomized phase II trial, pre/perimenopausal women with clinically aggressive HR+/HER2- ABC were randomly assigned 1:1 to first-line ribociclib (600 mg once daily; 3 weeks on, 1 week off) plus letrozole/anastrozole and goserelin or investigator's choice of combination CT (docetaxel plus capecitabine, paclitaxel plus gemcitabine, or capecitabine plus vinorelbine). The primary end point was progression-free survival (PFS).

Results: Among 222 patients randomly assigned to ribociclib plus ET (n = 112) or combination CT (n = 110), 150 (67.6%) had symptomatic visceral metastases, 41 (18.5%) had rapid disease progression per investigator's judgment, and 31 (14.0%) had symptomatic nonvisceral disease. Overall, 106 (47.7%) patients had investigator-assessed visceral crisis. The median follow-up time was 37.0 months. At data cutoff, 31.3% (ribociclib arm) and 15.5% (CT arm) of patients had completed study treatment and transitioned to post-trial access. The median PFS was 21.8 months (ribociclib plus ET; [95% CI, 17.4 to 26.7]) and 12.8 months (combination CT; [95% CI, 10.1 to 18.4); hazard ratio, 0.61 [95% CI, 0.43 to 0.87]; P = .003. The overall response rates and the median time to response in the ribociclib versus CT arms, respectively, were 66.1% and 61.8% and 4.9 months and 3.2 months (hazard ratio, 0.76 [95% CI, 0.55 to 1.06]). Lower rates of symptomatic adverse events were observed in the ribociclib versus CT arm.

Conclusion: First-line ribociclib plus ET showed a significant PFS benefit, similar response rates, and better tolerability over combination CT in patients with clinically aggressive HR+/HER2- ABC.

Trial registration: ClinicalTrials.gov NCT03839823.

FIG 1.

CONSORT diagram. AE, adverse event; CT, chemotherapy; ET, endocrine therapy; PD, progressive disease.

FIG 2.

Kaplan-Meier analysis of (A) PFS, (B) TTF, (C) TTR, and (D) OS. CT, chemotherapy; ET, endocrine therapy; OS, overall survival; PFS, progression-free survival; TTF, time to treatment failure; TTR, time to response.

FIG 3.

Subgroup analysis of PFS. The results from subgroups with small patient numbers (disease-free interval <2 years and low [<50] estrogen receptor–positive status) need to be interpreted with caution. CT, chemotherapy; ET, endocrine therapy; PFS, progression-free survival.