RecruitingPhase 2Drug trialEfficacy 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)To compare the efficacy and safety of ribociclib in combination with aromatase inhibitor and physician's choice of chemotherapy sequential endocrine therapy in the first-line treatment of ER medium to low expression/HER2-negative advanced breast cancer.