Updated results from MONALEESA-2, a phase 3 trial of first-line ribociclib + letrozole in hormone receptor-positive (HR+), HER2-negative (HER2–), advanced breast cancer (ABC).

• DOI: 10.1200/jco.2017.35.15_suppl.1038
• Publication Date: 2018-09-06T15:38:57Z
• Authors: Gabriel N. Hortob...; Salomon M. Stemmer; Howard A. Burris; Yoon Sim Yap; Gabe S. Sonke; Shani Paluch-Shimon; Mario Campone; Katarina Petrakova; Kimberly L. Black...; Eric P. Winer; Wolfgang Janni; Sunil Verma; Pier Franco Conte; Carlos L. Arteaga; David A. Cameron; Fengjuan Xuan; Michelle Kristine...; Caroline Germa; Samit Hirawat; Joyce O'Shaughnessy
• Keywords: Letrozole; Clinical endpoint; Progression-free survival; Interim analysis

1038 Background: Endocrine therapy (ET) is the basis of first-line (1L) treatment for HR+ ABC. However, ET resistance are almost universal. At first interim analysis (IA) MONALEESA-2 (NCT01958021), ribociclib (RIB; cyclin-dependent kinase 4/6 inhibitor) + letrozole (LET) significantly prolonged progression-free survival (PFS) vs placebo (PBO) LET in patients (pts) with HR+, HER2– 1 Here we report updated efficacy and safety data from a further ~11 months follow-up. Methods: Postmenopausal women no prior ABC were randomized 1:1 toRIB (600 mg/day, 3-weeks-on/1-week-off) LET(2.5 continuous) PBO LET. The primary endpoint was locally assessed PFS. Secondary endpoints include overall (OS; key) safety. OS significance defined by p-value threshold 3.15 x 10 -5 . Tumor assessments performed every 8 weeks 18 months, 12 weeks, thereafter. Results: 668 pts enrolled (334 each arm). second IA (data cut-off Jan 2, 2017), median duration follow-up 26.4 months; 116 deaths 345 PFS events had occurred. remain immature, 15.0% 19.8% pt RIB arm (HR = 0.746; 95% CI: 0.517–1.078; p= 0.059). Updated analyses confirmed continued benefit arm. 24-month rates (RIB LET) 54.7% 35.9%. Treatment consistent across subgroups. most common Grade 3/4 laboratory abnormalities (≥10% pts; decreased neutrophils (62.6% 1.5%), leukocytes (36.8% lymphocytes (16.2% 3.9%), elevated alanine aminotransferase (11.4% 1.2%). Conclusion: After 26+ follow-up, 1LRIB persists postmenopausal study remains immature analysis. profile manageable. 1. Hortobagyi G, et al. N Engl J Med 2016;375:1738–48. Clinical trial information: NCT01958021.