Advanced Breast Cancer Study of CDK4/6 Inhibitor Combined With Endocrine Therapy Endocrine Therapy in HR+/HER2- Advanced Breast Cancer

Study Overview
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Brief Summary
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By retrospectively collecting and arranging real-world data of multi-center HR+/HER2- advanced breast cancer in China combined with CDK4/6 inhibitor and endocrine therapy, we analyzed different HER2 expression levels (HER2 0, 1+, 2+ and FISH-), especially Clinical outcomes of endocrine therapy for metastatic breast cancer with low HER2 expression (HER2 1+, 2+ and FISH-), exploring potential biomarkers of CDK4/6 inhibitors, and understanding the outcome characteristics of HER2 heterogeneity in MBC through multivariate analysis , and guide clinical application.

Official Title
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A Multicenter Clinical Study Evaluating Real-world CDK4/6 Inhibitor Combined With Endocrine Therapy in HR+/HER2- Advanced Breast Cancer

Conditions
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Advanced HR+ HER2 Negative Breast Carcinoma

Intervention / Treatment
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* Drug: (CDK)4/6 inhibitor


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 1) Female patients with advanced breast cancer aged ≥18 years. 2) For breast cancer patients diagnosed as HR-positive and HER2-negative by pathological examination, the expression levels of ER, PR, and HER2 were reported by immunohistochemistry in the primary or metastatic lesions. ER positivity and/or PR positivity is defined as: the proportion of tumor cells with positive staining accounts for ≥ 10% of all tumor cells (confirmed by the investigator of the trial center); HER2 negative is defined as: standard immunohistochemistry (IHC) test is 0/1+; HER2 (2+) needs to be tested by FISH, HER2/CEP17 ratio is less than 2.0 or HER2 gene copy number is less than 4 (by the test center of the test center) Investigator review and confirmation). 3) CDK4/6 inhibitors combined with endocrine therapy can conduct complete efficacy evaluation and follow-up information collection. 4) Postmenopausal or premenopausal/perimenopausal female patients can be enrolled. Postmenopausal status, defined as meeting at least one of the following criteria: prior bilateral ovarian surgery; age ≥60 years; age <60 years, menopause for at least 12 months (not due to chemotherapy, tamoxifen, toremide) fen or ovarian suppression) and follicle-stimulating hormone (FSH) and estrogen levels are in the postmenopausal range. Premenopausal or perimenopausal women may also be enrolled, but must be willing to receive LHRHa during the study period. 5) According to RECIST 1.1 criteria, patients must have: a) measurable lesions; b) unmeasurable osteolytic or mixed (osteolytic + osteoblastic) bone lesions in the absence of measurable lesions. Exclusion Criteria: 1) Early breast cancer patients receive CDK4/6 inhibitor drug therapy. 2) HER2 overexpression or gene amplification, such as immunohistochemical score 3+ or positive fluorescence in situ hybridization. 3) Pregnant or lactating female patients. 4) Patients deemed unsuitable for inclusion by the investigator.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: HR+/HER2- advanced breast cancer patients receiving CDK4/6 inhibitor combined with endocrine therapy<br>According to clinical guidelines or drug instructions, the treating physician will adjust the drug dose in accordance with the clinical reality and the patient's personal situation. | Drug: (CDK)4/6 inhibitor<br>* CDK4/6 inhibitor + AI/fulvestrant therapy，According to clinical guidelines or drug instructions, the treating physician will adjust the drug dose in accordance with the clinical reality and the patient's personal situation.<br>* Other names: ET;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Progression-free survival (PFS) From enrollment to progression or death (for any reason) Progression-free survival (PFS) | From enrollment to progression or death (for any reason) | Estimated 24 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Objective response rate (ORR) | Ratio of CR and PR in all subjects | Estimated 24 months | 
| Disease Control Rate (DCR) | Ratio of CR ,PR and SD in all subjects | Estimated 24 months | 
| Overall survival (OS) | From enrollment to death (for any reason) | Estimated 36 months |