The recommended dosage of pegylated recombinant human granulocyte-colony stimulating factor (PEG-rhG-CSF) for Western chemotherapy patients is 6 mg per cycle. However, for Eastern Asians, the optimal dose remains unknown. This open-label, randomized, non-inferiority trial (NCT05283616) enrolled Chinese female breast cancer patients receiving adjuvant chemotherapy. Participants were randomized to receive either 3 or 6 mg of PEG-rhG-CSF per cycle, stratified by body weight (BW; ≤60 kg vs. >60 kg).