Abstract: Objective To retrospectively analyze the incidence and influencing factors of Trastuzumab⁃induced cardiovascular toxicity among breast cancer patients and to explore the risk stratification efficacy of the Heart Failure Association (HFA) of the European Society of Cardiology⁃International Cardio⁃Oncology Society (ICOS) score. Methods This analysis included 298 patients with human epidermal growth factor receptor 2 (HER2)⁃positive breast cancer who received Trastuzumab treatment at the First Affiliated Hospital of Dalian Medical University between June 2012 and June 2024. Baseline risk assessment for cancer therapy⁃related cardiovascular toxicity (CTR⁃CVT) was performed using the HFA⁃ICOS score recommended by the 2022 European Society of Cardiology guidelines, categorizing patients into low⁃, intermediate⁃, high⁃, and very⁃high⁃risk groups. Univariable analysis and multivariable Logistic regression  model were used to identify risk factors for cardiovascular toxicity. Results Among the 298 patients, the incidence of Trastuzumab⁃related cardiovascular toxicity was 7.4% (22/298), including arrhythmias (68.2%, 15/22), cancer therapeutics⁃related cardiac dysfunction (27.3%, 6/22), and vascular toxicity (4.5%, 1/22). Independent risk factors for cardiovascular toxicity in HER2⁃positive breast cancer patients treated with Trastuzumab were identified as Ki⁃67 ≥30%, anthracycline⁃containing regimens, and smoking history (all P<0.05). The HFA⁃ICOS score indicated that the incidence of CTR⁃CVT in high⁃risk patients (25.0%) was higher than in low⁃risk (5.6%) and medium⁃risk (9.6%) patients. Conclusions Trastuzumab⁃related cardiovascular toxicity primarily manifests as arrhythmias, with associated risk factors including anthracycline use, smoking history, comorbid coronary heart disease, and Ki⁃67≥30%. Clinically, the HFA⁃ICOS score can be utilized for risk stratification to implement differentiated monitoring.

Key words: HER2?positive breast cancer, Trastuzumab, Cardiovascular toxicity, HFA?ICOS score