This is a single-arm study planned to enroll 56 breast cancer patients who experienced grade 2 or higher thrombocytopenia following prior chemotherapy and achieved normalization (platelet count ≥100 × 109/L and ≥200 × 109/L) through intervention.

Inclusion：

• Age 18-75 years, any gender;
• Pathologically diagnosed with breast cancer based on histological or cytological examination, and previously treated with neoadjuvant anti-HER-2 therapy followed by T-DM1 adjuvant therapy;
• Experienced grade 2 or higher tumor treatment-related thrombocytopenia during the previous T-DM1 treatment cycle, with platelet count restored to ≥100 × 109/L and ≤200 × 109/L prior to the next treatment;
• ECOG performance status score: 0-2;
• Planned to undergo at least two additional treatment cycles including T-DM1 administration, with the dose of T-DM1 in the current cycle consistent with the previous cycle;
• Expected survival of ≥12 weeks and able to tolerate the current treatment regimen for at least two cycles or more;
• Expected to have good compliance, able to follow up on treatment efficacy and adverse reactions as required by the protocol.

Exclusion:

• A history of other malignant tumors diagnosed within the past 3 years;
• Patients with mental or neurological disorders who are unable to cooperate;
• Patients who are scheduled to undergo or have previously undergone organ or bone marrow transplantation;
• Patients with hematopoietic system disorders other than chemotherapy-induced thrombocytopenia (CTIT), including but not limited to leukemia, primary immune thrombocytopenia, myeloproliferative disorders, multiple myeloma, and myelodysplastic syndrome;
• Patients with a history of any arterial or venous thrombotic events within the past 6 months prior to screening;
• Severe bleeding manifestations within 2 weeks prior to screening, such as gastrointestinal or central nervous system bleeding;
• Participation in a clinical trial of the same type of drug within 4 weeks prior to enrollment;
• Pregnant or lactating women;
• Patients with a history of hypersensitivity to the study drug;
• Patients deemed ineligible by the investigator.

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