A 62-year-old woman who received chemotherapy for breast cancer eight years ago develops progressive exertional dyspnea. Echocardiography shows biventricular dilation with global hypokinesia, LVEF 28%. Coronary angiography is normal. Which agent is the most likely cause?
- A Cyclophosphamide
- B Trastuzumab
- C Doxorubicin ✓
- D Cisplatin
Correct answer: C. Doxorubicin
Explanation
Anthracyclines such as doxorubicin cause dose-dependent, cumulative, type I cardiotoxicity through free radical generation and myocyte apoptosis, producing an irreversible dilated cardiomyopathy that may appear years after exposure. Trastuzumab causes type II toxicity, which is a reversible functional depression without structural myocyte loss, making it the key distractor. Cyclophosphamide causes acute hemorrhagic myocarditis at very high doses, not delayed dilation.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
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