336PInterim results from CompLEEment-1 (A phase IIIb study of ribociclib and letrozole as first-line therapy for advanced breast cancer in an expanded population): Spanish cohort results

Abstract Background In Spain luminal metastatic Breast Cancer accounts for more than 3000 deaths yearly. Ribociclib+letrozole has shown efficacy on prolonging progression free survival (PFS) vs placebo+letrozol in two phase 3 trials. However, data on efficacy and tolerability is lacking for a broader population. We present interim data from CompLEEment-1, an ongoing, open-label, phase 3b trial evaluating ribociclib+letrozole as first-line endocrine therapy in an expanded population of patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–) advanced breast cancer (ABC). Methods Patients treated with ≤1 line of prior chemotherapy and no prior endocrine therapy for advanced disease received ribociclib 600 mg/day (3-weeks-on/1week-off) + letrozole (2.5 mg/day; plus monthly goserelin or leuprolide in men and premenopausal women). The primary objective was safety and tolerability. Here we report a sub-analysis of CompLEEment-1 for the Spanish population. Results 526 patients were evaluated over a median follow-up of 10.3 months. Baseline characteristics indicated a diverse population with median age of 55.6 years (range 24-85); 0.8% of patients were male, 34.6% female pre-menopausal and 64.6% female post-menopausal. 71% had visceral metastasis, in 8 cases at the CNS. 55.9% had measurable disease at baseline. The rate of all-grade and grade ≥ 3 treatment-related adverse events (AEs) was 98.5% and 70.0%, respectively. Treatment-related serious AEs occurred in 12.2% of patients. All-grade and grade ≥ 3 AEs leading to ribociclib discontinuation occurred in 13.7% and 8.2% of patients, respectively. Rates of ≥ 3 AEs of special interest (AESI) were 59.5% for neutropenia, 6.8% for increased alanine aminotransferase, 4.8% for increased aspartate aminotransferase, and 0.6% for QTcF prolongation. Patient health-related quality of life was maintained versus baseline. Conclusions Initial results from the Spanish cohort in CompLEEment-1 are consistent with previous data showing efficacy and a manageable safety profile of ribociclib plus letrozole as a first-line treatment option in a diverse group of patients with HR+, HER2– ABC. Acknowledgement: Dr. J. Gavila-Gregori, Dr. M.J. Martinez-Serrano and Dr. M. Perello contributed equally to this study. Clinical trial identification NCT02941926. Legal entity responsible for the study Novartis Pharmaceuticals Corporation. Funding Novartis Pharmaceuticals Corporation. Disclosure E.M. Ciruelos: Advisory / Consultancy, Speaker Bureau / Expert testimony, Speaker and ad.board honoraria: Novartis; Advisory / Consultancy, Speaker Bureau / Expert testimony, Speaker and ad.board honoraria: Lilly; Advisory / Consultancy, Speaker Bureau / Expert testimony, Speaker and ad.board honoraria: Roche; Advisory / Consultancy, Speaker Bureau / Expert testimony, Speaker and ad.board honoraria: Pfizer. R. Villanueva Vazquez: Advisory / Consultancy: Novartis; Advisory / Consultancy: Pfizer; Advisory / Consultancy: Roche. F. Moreno: Advisory / Consultancy, Travel / Accommodation / Expenses: Novartis; Advisory / Consultancy, Travel / Accommodation / Expenses: Pfizer; Advisory / Consultancy, Travel / Accommodation / Expenses: Roche; Advisory / Consultancy: AstraZeneca; Advisory / Consultancy: Eisai; Advisory / Consultancy: MSD. I. Alvarez: Research grant / Funding (institution): Novartis; Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: Roche. S. Gonzalez-Santiago: Research grant / Funding (institution): Novartis; Research grant / Funding (institution): Roche; Research grant / Funding (institution): Eisai; Research grant / Funding (institution): AstraZeneca. A. Barnadas: Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: Roche; Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: Novartis; Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: Pfizer; Research grant / Funding (institution): Bristol-Myers Squibb; Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: AstraZeneca; Research grant / Funding (institution): Lilly; Advisory / Consultancy, Travel / Accommodation / Expenses: Eisai; Advisory / Consultancy, Travel / Accommodation / Expenses: Genomic Health; Advisory / Consultancy, Travel / Accommodation / Expenses: Pierre Fabre. B. Cantos: Research grant / Funding (institution), Study enrollment: Fundacion para la Investigacion del Hospital Puerta de Hierro de Majadahonda; Advisory / Consultancy: Novartis; Advisory / Consultancy: Roche; Advisory / Consultancy: Celgene; Advisory / Consultancy: AstraZeneca. M. Bellet Ezquerra: Advisory / Consultancy: Novartis; Advisory / Consultancy: Pfizer; Advisory / Consultancy: Lilly. M. Martin: Advisory / Consultancy, Research grant / Funding (institution): Novartis; Advisory / Consultancy, Research grant / Funding (institution): Roche; Advisory / Consultancy: Lilly; Advisory / Consultancy: Pfizer; Advisory / Consultancy: Pharmamar; Advisory / Consultancy: Taiho Oncology; Advisory / Consultancy: Amgen; Advisory / Consultancy: AstraZeneca; Advisory / Consultancy, Research grant / Funding (institution): Puma. N. Martinez: Research grant / Funding (institution): Roche; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Eisai; Research grant / Funding (institution): AstraZeneca. All other authors have declared no conflicts of interest.