This study is a multicenter, single-arm, open-label Phase II exploratory clinical trial designed to evaluate whether prophylactic use of leucogen can reduce the incidence of Grade 3 or higher neutropenia in early-stage HR+/HER2- breast cancer patients receiving ribociclib combined with endocrine therapy. The study plans to enroll 97 patients using a Simon two-stage design, with the primary endpoint being the incidence of severe neutropenia within 4 treatment cycles (4 months) after initiation. Secondary endpoints include the incidence of all-grade neutropenia, febrile neutropenia, ribociclib treatment intensity, and safety. The study will systematically assess the preventive efficacy and safety of leucogen to provide a basis for subsequent Phase III randomized controlled trials.
The patient has signed and dated the informed consent form.
Age > 18 years at the time of signing informed consent.
The patient is a female with known menopausal status at the time of signing informed consent or initiation of adjuvant endocrine therapy (whichever is earlier). Postmenopausal status is defined as: bilateral oophorectomy, age > 60 years, or age < 60 years with amenorrhea ≥ 12 months (in the absence of chemotherapy, tamoxifen, toremifene, or ovarian suppression), and follicle-stimulating hormone and plasma estradiol levels within the local postmenopausal normal range.
Histologically confirmed unilateral primary invasive breast cancer, with the date of initial cytological or histological diagnosis within 18 months before enrollment. Patients with multicentric and/or multifocal tumors are eligible if all pathologically examined lesions meet criteria 5 and 6 below.
Previous treatment with any CDK4/6 inhibitor.
Use of tamoxifen, raloxifene, or aromatase inhibitors for breast cancer risk reduction ("chemoprevention") and/or osteoporosis treatment within 2 years before signing informed consent.
Prior anthracycline cumulative dose reaching or exceeding: doxorubicin 450 mg/m², or epirubicin 900 mg/m².
Known hypersensitivity to any excipient of ribociclib and/or the endocrine therapy and/or leucogen (e.g., rare hereditary galactose intolerance, Lapp lactase deficiency, glucose-galactose malabsorption, or soy allergy).