Mecapegfilgrastim for the Prevention of Dalpiciclib -Induced Neutropenia in Advanced Breast Cancer

Inclusion criteria

• Age ≥18.
• Pathologically confirmed advanced HR+/HER2- breast cancer: there is evidence of focal recurrence or metastasis, which is not suitable for surgical resection or radiotherapy for the purpose of cure.
• No more than one line of chemotherapy is allowed for patients with recurrent and metastatic diseases.
• Eastern Cooperative Oncology Group (ECOG) performance status 0-2.
• For patients with brain metastases, there is need for local treatment, and the brain lesions are stable for ≥ 3 months, and no need for dexamethasone or mannitol.
• Adequate organ function: (I) adequate hematologic function: hemoglobin ≥90 g/L, absolute neutrophil count (ANC) ≥1.5×109/L, platelet count (PLT) ≥100×109/L; (II) adequate renal and hepatic function.
• Negative pregnancy test.

Exclusion criteria

• Previous pathological diagnosis of HER2 positive breast cancer.
• Previous treatment with cdk4/6 inhibitors.
• Major surgery, chemotherapy, radiotherapy, any research drug or other anti-cancer treatment within 2 weeks before entering the trial.
• Any other malignant tumor diagnosed within 3 years before entering the study, except non-melanoma skin cancer, basal cell or squamous cell skin cancer or cervical carcinoma in situ after radical treatment.
• Human immunodeficiency virus (HIV) infection or known acquired immunodeficiency syndrome (AIDS), active hepatitis B (HBV DNA ≥ 1000 IU/ml), hepatitis C (HCV antibody positive and HCV-RNA higher than the detection limit of the analytical method) or combined hepatitis B and hepatitis C co-infection.
• Within 6 months before entering the study, the following conditions occurred: myocardial infarction, severe / unstable angina pectoris, NYHA grade 2 or above cardiac insufficiency, persistent arrhythmia ≥ grade 2 (according to nci-ctcae version 5.0), atrial fibrillation at any level, coronary / peripheral artery bypass grafting, symptomatic congestive heart failure, cerebrovascular accident (including transient ischemic attack or symptomatic pulmonary embolism).
• Inability to swallow, intestinal obstruction or other factors affecting drug administration and absorption.