Abstract P6-18-17: Ribociclib + letrozole in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–) advanced breast cancer (aBC) with no prior endocrine therapy (ET) for ABC: CompLEEment-1 trial, preliminary results from Spanish population
Authors: Salvador J , Ciruelos EM , Prat A , Jiménez-Rodríguez B , de la Cruz L , Martínez N , Villanueva Vázquez R , de Toro R , Antón A , Moreno F , Alvarez I , Gavila J , Quiroga V , Vicente E , de la Haba J , González-Santiago S , Díaz N , Barnadas A , Cantos Sánchez de Ibargüen B , Delgado JI , Bellet M , Gimeno A , Sanz S , Martin M 
Published: May 2019

Background: The phase III Monaleesa-2, Monaleesa-3 and Monaleesa-7 trials have shown significantly improved PFS for the combination ribociclib + ET vs ET + placebo in pre-, peri-, and postmenopausal women with HR+/HER2–, first and second line aBC. The Compleement-1 trial is a phase IIIb, single-arm, open-label, international study to assess the safety and efficacy of ribociclib + letrozole in men and women who have not received prior ET for HR+, HER2– ABC [J Clin Oncol 36, 2018 (suppl; abstr 1056)].

Methods: 526 patients with HR+, HER2– ABC, ≤1 line of prior CT, and no prior ET for aBC were enrolled in the Compleement-1trial in Spain from April 2017 to January 2018. Patients received ribociclib (600 mg/day, 3 weeks on/1 week off) + letrozole (2.5 mg/day); men and premenopausal women received concomitant goserelin (3.6 mg subcutaneous implant every 28 days). The primary objective was safety and tolerability. Here we report on a sub-analysis from the Spanish population of Compleement-1 trial including baseline characteristics and early safety results for the first patients enrolled who completed at least 56 days of follow-up or discontinued before the cut-off date (3rd Oct 2017).

Results: One hundred fifty four patients constituted the analytical cohort for this sub-analysis. Demographics and baseline characteristics: median age was 52 years (range 24-82); 1% of patients were male, 31.8% female pre-menopausal and 67.5% female post-menopausal; 44.2% vs 38.3% of patients had visceral disease vs bone only disease; 49.9% patients had ≥2 metastatic sites; and 34.4% of patients presented as de novo stage IV. The median exposure for study treatment was 1.8 months (range 0.8-1.8). The grade 3/4 events reported &gt;1% included neutropenia (50%), increased GGT levels (3.2%), leukopenia (1.3%), and increased ALT (1.3%). QTcF prolongation &gt;480ms based on ECG data was reported in 1.2% patients. Median dose intensity for ribociclib was 600mg/day (range 476.5-600); 11% of patients required one dose reduction (8.4% due to AEs), 59.7% had at least one dose interruption (57.1% due to AEs) and 9.7% were permanently discontinued (4.5% due to AEs).

Conclusions: Preliminary safety results from this Compleement-1 sub-analysis including Spanish population are consistent with previous data presented from Monaleesa-2, Monaleesa-3, Monaleesa-7 and Compleement-1. These data support the predictable and manageable safety profile of ribociclib in combination with letrozole. Clinical trial information: NCT02941926

Citation Format: Salvador J, Ciruelos EM, Prat A, Jiménez-Rodríguez B, de la Cruz L, Martínez N, Villanueva Vázquez R, de Toro R, Antón A, Moreno F, Alvarez I, Gavila J, Quiroga V, Vicente E, de la Haba J, González-Santiago S, Díaz N, Barnadas A, Cantos Sánchez de Ibargüen B, Delgado JI, Bellet M, Gimeno A, Sanz S, Martin M. Ribociclib + letrozole in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–) advanced breast cancer (aBC) with no prior endocrine therapy (ET) for ABC: CompLEEment-1 trial, preliminary results from Spanish population [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-18-17.