Exploration of the Efficacy and Safety of Different - Cycle Neoadjuvant Treatment with Rekan Trastuzumab in Early - stage HER2 - positive Breast Cancer: A Two - Cohort, Exploratory Study

INTERVENTION: Column 1:Trastuzumab Rezetecan 6 cycles;Column 2:Trastuzumab Rezetecan 8 cycles; CONDITION: Stage II‐III HER2‐positive breast cancer PRIMARY OUTCOME: Total Pathological Complete Response; SECONDARY OUTCOME: event free survival;Breast Pathological Complete Response;residual cancer burden; INCLUSION CRITERIA: 1.Female patients with newly diagnosed breast cancer who are aged 18 years or older and 70 years or younger; 2.According to the latest ASCO/CAP guidelines, early or locally advanced HER2‐positive invasive breast cancer that has been confirmed by histopathological examination, and which meets the following conditions: HER2 positive: IHC 3+ or IHC 2+ but ISH is positive; tumor stage: II‐III stage; 3.The known status of hormone receptors; 4.ECOG score 0‐1; 5.According to the RECIST 1.1 standard, there is at least one measurable lesion present; 6.The functional levels of the organs must meet the following requirements: 1) Blood routine: Neutrophil count (ANC) = 1.5×10^9/L (no use of hematopoietic stimulating factor drugs within 14 days before the first administration of the study); Platelet count (PLT) = 100×10^9/L (no blood transfusion within 14 days before the first administration of the study); Hemoglobin (Hb) = 90 g/L; 2) Blood biochemistry: Total bil