RecruitingPhase 2Drug trialHerombopag Treated T-DM1 Induced Platelet ReductionThis 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.