Real-World Study on CDK4/6 Inhibitors Combined With Endocrine Therapy and Subsequent Treatment in HR+/HER2- MBC.

Inclusion Criteria

• •* Age ≥ 18 years, postmenopausal or pre/perimenopausal females, or male patients. Female patients must meet one of the following criteria:
• •1. Prior bilateral oophorectomy or age ≥ 60 years.
• •2. Age \< 60 with natural postmenopausal status (defined as spontaneous cessation of regular menstruation for at least 12 consecutive months without any other pathological or physiological reasons), and estradiol (E2) and follicle-stimulating hormone (FSH) levels consistent with postmenopausal range.
• •3. Pre/perimenopausal females may also be eligible but must be willing to receive LHRH agonist during the study.
• •* Pathologically confirmed HR-positive male/female breast cancer patients with evidence of localized recurrence or metastasis, who are not suitable for curative surgery or radiation therapy:
• •ER-positive and/or PR-positive defined as the proportion of positively stained tumor cells ≥ 1% of all tumor cells (as confirmed by the investigators at the participating center).
• •Eastern Cooperative Oncology Group (ECOG) performance status of 0-2.
• •No prior systemic treatment or currently receiving CDK4/6 inhibitors as first-line treatment for advanced disease.
• •Reproductive-age females must have a negative serum pregnancy test within 28 days before enrollment and male/female patients must be willing to use a medically approved highly effective contraceptive measure during the study period and up to 1 year after the last dose of investigational drug.
• •Non-pregnant or non-lactating females.
• •Not concurrently participating in any other ongoing study.
• •Patient or legally authorized representative has provided informed consent and is willing and able to comply with the planned visits, study treatment plan, laboratory tests, and other trial procedures.