⁃ Postmenopausal/premenopausal women aged ≥18 years and ≤70 years;

⁃ HR + / HER2 breast cancer confirmed by histology (note: her2-negative is defined as: (1) IHC1 + / IHC0; ②IHC2+ : FISH-);

⁃ Confirmed by the histology of locally advanced breast cancer (local treatment) to radical or recurrent metastatic breast cancer;

⁃ In the late stage of untreated or experienced a CDK4/6 with endocrine therapy of patients;

⁃ Researchers think that for selecting patients with chemotherapy (step 2022 guidelines recommend for internal transfer, always endocrine therapy resistance or preferred to rescue patients with endocrine therapy best choice of chemotherapy);

⁃ One line finish cycle disease after chemotherapy (4 to 8 cycles) to alleviate or stable, quasi follow-up maintenance treatment: a. late stage A gleam of unused CDK4/6 inhibitors + endocrine group subjects into the queue for A; b. Used in the late phase line CDK4/6 inhibitors queue B + endocrine subjects into groups;

⁃ Into the former group at least one measurable lesions (RECIST v1.1 standard); 8.ECOG score 0 to 2 points;

• Always all the acute toxic reaction caused by antineoplastic therapy in screening before easing to 0 and 1 level (according to the NCI CTCAE 5.0 judgment; Hair loss, other than toxicity that the investigator believes does not pose a safety risk to the subject); 10. Functions: bone marrow neutrophils absolute acuity 1.5 x 109 / L, platelet acuity 100 x 109 / L, 90 g/L or higher hemoglobin; 11. Liver and kidney function: TBIL acuities were 1.5 x ULN; ALT and AST≤2.5 x ULN; In case of liver metastasis, ALT and AST≤ 5×ULN; BUN and Cr≤1.5×ULN and creatinine clearance ≥50 ml/min; 12.Voluntary participation in the clinical trials, signed written informed consent.