451P Breast Cancer Lighthouse Study: 1 Year Follow-Up Results of Ribociclib Treatment Patterns and Clinical Outcomes in a Real-World Portuguese Cohort

CDK4/6 inhibitor treatment in advanced breast cancer (ABC) has shown benefit in progression-free survival (PFS) and another clinical endpoints in landmark clinical trials. This study aims to comprehend real-world use of ribociclib, effectiveness and safety in the Portuguese population. Retrospective-prospective study of Portuguese cohort adult women with HR+/HER2- ABC treated with ribociclib through 3 years. Ribociclib treatment patterns, PFS at 1 year follow-up after ribociclib initiation and others secondary endpoints are reported. Data collection began in January 2019 with analysis cut-off in March 2023. Confidence intervals and survival analyses were performed using R® software. Of the 270 patients included, 64 (23.7%) were pre/peri-menopausal and 206 (76.3%) were post-menopausal patients. Median follow-up duration was 11.9 months. Baseline characteristics were described previously. Regarding treatment patterns, 207 (76.7%) received ribociclib as first-line [61 (22.6%) de novo patients and 146 (54.1%) after prior therapy], 40 (14.8%) as a second line and 23 (8.5%) after second line. During first year’s follow-up, mean ribociclib dose was of 488.4 [468.6; 508.2] and 114 (42.4%) patients reported dose adjustments. Of these 85 (74.6%) had a single dose adjustment. Patients had an average number of 12.1±5.3 clinical appointments, a mean of 3.4±2.5 imaging exams and 178 patients (65.9%) performed ECGs. Disease progression/death was experienced by 88 in 261 patients at a median of 407 days after ribociclib initiation, with a survival rate at 12 months of 0.782±0.027. At 12 months, complete response was achieved in 15 patients (5.6%), 80 patients (29.6%) had partial response and 52 (19.3%) remained stable. At cut-off, 175 (64.8%) patients were still being treated with ribociclib. Most common reasons for ribociclib discontinuation: disease progression (64, 67.4%) and AEs (21, 22.1%). Most common AEs were neutropenia (320, 42.3%), anemia (50, 6.6%), fatigue/asthenia (44, 5.8%), and leukopenia (42, 5.5%). This is the first cohort of Portuguese patients to provide efficacy and safety data in a real-world setting, demonstrating similar clinical trial outcomes.