Reachaut: First-Line (1l) Ribociclib (Rib) Plus Endocrine Therapy (Et) In Hr+, Her2-Metastatic Breast Cancer (Mbc) In The Real-World Setting.

e12527 Background: RIB + aromatase inhibitor (AI) is approved as 1L treatment (tx) for HR+, HER2− MBC. Real-world data on efficacy and safety of RIB+AI are limited. REACHAUT, a prospective, noninterventional trial assessed the safety of RIB+AI in 1L setting in postmenopausal patients (pts) with HR+, HER2− MBC in a real-world setting. First interim analysis results about safety are presented. Methods: 75 postmenopausal pts with HR+, HER2− MBC, QTc < 450 msec, and no prior ET for advanced disease were enrolled at 13 sites. 1L chemotherapy (CT) was allowed. Results: At data cutoff (25-Jan-2019), 61 pts were evaluable for safety (ongoing, n = 44; discontinued, n = 17). Median duration of follow-up was 29 d. Median age at baseline was 65 y ( < 65 y, n = 28; ≥65 y, n = 33); ECOG performance status was 0 (n = 39) and 1 (n = 12). 42.6% had visceral (lung, liver) metastases (mets), while 34.4% had bone only mets. Most common prior tx included CT (29.5% in neoadjuvant/adjuvant/metastatic setting) and ET (41%). Pts received RIB in 1L (93.4%) and second-line (6.6%) setting. In 80.3% pts receiving RIB, the ET partner included letrozole (57.4%), exemestane (11.5%), anastrozole (9.8%). Median duration of RIB exposure was 100 d. Median time to first AE was 14 d. 83.6% pts experienced AEs with mild (63.9%) to moderate (50.8%) severity. Serious AEs were noted in 6.6% pts. Most common AEs were neutropenia (42.6%) and QTc prolongation (24.6%). 4.9% pts had hepatobiliary AEs. Due to AEs, dose adjustments (4.9%) and dose interruptions (19.8%) were needed. No deaths were reported; median PFS was not reached. Subgroup analysis by age ( < 65 y vs ≥65 y) showed that the incidence of AEs was 55.9% vs 44.1%. Neutropenia was reported in 46.4% pts aged < 65 y vs 39.3% pts aged ≥65 y; QT prolongation events were noted in 21.4% pts aged < 65 y vs 27.2% pts aged ≥65 y. Dose adjustments and dose interruptions were needed in 14.3% and 46.4% pts aged < 65 y vs 15.2% and 45.5% pts aged ≥65 y. Conclusions: Overall safety of RIB+AI in routine clinical practice in REACHAUT was consistent with that reported in the MONALEESA-2 study. In real-world setting, pt age ( < 65 y vs ≥65 y) had minimal impact on AEs. Clinical trial information: NIS006622.