First-Line Ribociclib Plus Endocrine Therapy Versus Chemotherapy With or Without Subsequent Endocrine Therapy in Patients With Rapidly Progressive HR-Positive/HER2-Negative Advanced Breast Cancer

This phase II study focuses on women with rapidly progressive hormone receptor-positive and HER2-negative advanced breast cancer, including patients with symptomatic visceral metastases, rapidly increasing tumor burden, impending organ dysfunction, or highly symptomatic non-visceral disease. These patients often require prompt and effective systemic treatment. The purpose of the study is to determine whether first-line ribociclib combined with endocrine therapy can provide effective and rapid tumor control compared with chemotherapy-based treatment. Women in the prospective study group receive ribociclib plus endocrine therapy, with ovarian function suppression when clinically indicated. Their outcomes are compared with data from patients previously treated at the same participating hospitals with combination chemotherapy, with or without subsequent endocrine maintenance therapy. The main outcome is the objective response rate, defined as the proportion of patients whose tumors shrink or disappear. Other outcomes include progression-free survival, overall survival, clinical benefit, time to response, treatment safety, and quality of life.