Objective:To study the incidence and risk factors of the corrected QT (QTc) prolongation in breast cancer patients treated with anthracyclines.Methods:From July 2017 to January 2019, 279 female breast cancer patients who underwent 4 cycles of anthracycline treatment in Department of Breast Surgery of the People′s Hospital of Shanxi Medical University were enrolled in the study. The ECG of all patients before treatment showed sinus rhythm and QTc<440 ms. The most common electrocardiographic abnormalities after treatment were the changes of QTc. There were 78 cases with prolonged QTc (≥440 ms, QTc prolongation group) and 201 cases with normal QTc (<440 ms, non-prolongation group). The risk factors of QTc prolongation were analyzed by univariate and multivariate logistic regression. Cardiac toxicity was evaluated according to clinical symptoms and ECG results during treatment.Results:The common ECG abnormalities after treatment were 78 cases of QTc prolongation (28.0%), 22 cases of ST-T changes (7.9%), and 18 cases of sinus bradycardia (6.5%). Univariate analysis showed that there were significant differences in administration of anthracyclines(contained epirubicin in 48 and 73 cases, pirubicin in 10 and 33 cases, doxorubicin in 4 and 12 cases, liposomal doxorubincin in 16 and 83 cases,χ 2=15.54, P<0.01), dexrazoxane use (χ 2=5.43, P=0.02), coronary heart disease (χ 2=4.56, P=0.03), obesity or overweight (χ 2=4.51, P=0.03) between two groups. Multivariate logistic regression analysis showed that the use of different types of anthracyclines ( OR=1.42, 95 %CI: 1.37-1.48, P=0.02) and overweight/obesity ( OR=1.23, 95 %CI: 1.16-1.30, P=0.04) were independent risk facors of QTc prolongation. The liposomal doxorubicin in anthracyclines resulted in a minimum incidence of the QTc prolongation (16.2%, 16/99), while that of epirubicin was up to 39.7% (48/121). Preventive use of dexrazoxane reduced the incidence of the QTc prolongation to 11.4% (4/35). The incidence of the QTc prolongation in breast cancer with coronary heart disease or overweight/obesity was relatively high, which was 4/6 and 34.4%(42/122), respectively. No cardiotoxic symptoms such as chest pain, palpitation and shortness of breath occurred during the treatment, and no fatal arrhythmia such as ventricular tachycardia and ventricular fibrillation was observed in electrocardiogram. Conclusion:Although the incidence of the QTc prolongation in breast cancer patients treated with anthracyclines is high, there is no serious cardiotoxicity such as fatal arrhythmia. Breast cancer patients with coronary heart disease or overweight/obesity are more likely to have the QTc prolongation. Preventive use of dextrazoxan or the selection of liposomal doxorubicin can reduce the incidence of the QTc prolongation.