Real-world impact of dual anti-HER2 antibodies on cardiac function in patients with human epidermal growth factor receptor 2-positive metastatic breast cancer.

• 101 patients with HER2+ MBC on pertuzumab and trastuzumab were included. • Most observed cardiotoxicity were mild, all occurred early within 24 months. • Presence of cardiovascular co-morbidities predicts treatment cardiotoxicity.