Efficacy and Safety of Ribociclib Combined With AI Versus Physician&Amp;#39;s Choice of Chemotherapy Sequential Endocrine Therapy in ER Middle-low-expression/HER2-negative Advanced Breast Cancer (Rachel)

The main goal of this clinical trial is to compare in the efficacy of Ribociclib in combination with AI versus physician's choice of chemotherapy sequential endocrine therapy in ER medium to low expression/HER2-negative advanced breast cancer and evaluate the PCR DFS,OS and safety of the subjects. The main question it aims is comparing the efficacy and safety of first-line application of CDK4/6 inhibitors combined with initial endocrine therapy versus sequential endocrine therapy after chemotherapy induction therapy in ER medium to low expression/HER2- negative advanced breast cancer. This study is planned to include 190 patients with ER medium to low expression/HER2- negative advanced breast cancer between August 2024 and December 2025 who meet the entry criteria In this study, it is proposed to randomise the enrolled patients using stratified grouping + block randomisation method. The enrolled patients were firstly stratified based on (1) presence of visceral metastases and (2) disease-free interval ≤or ≥ 2 years assessment.