Real-world patterns of post-progression treatment and outcomes in patients with HR+/HER2− advanced breast cancer treated with CDK4/6 inhibitors

PATIENTS AND METHODS: we retrospectively collected data of patients with HR+/HER2- advanced breast cancer (ABC) treated with endocrine therapy (ET) and a CDK4/6 inhibitor (CDK4/6i) aiming to describe the patterns of post-progression outcomes. RESULTS: Among 452 evaluable patients 325 were treated in the first-line setting. Median progression-free survival (mPFS) was 22.8 months overall and 29.7 months in patients treated in first-line setting. Factors associated with outcomes in multivariate analysis were the line of CDK4/6i therapy, de novo vs recurrent disease, visceral vs bone-only metastases, and primary endocrine resistance.A total of 300 patients progressed and 250 overall and 156 in the first-line cohort received a subsequent treatment. Visceral progression and CDK4/6i duration