A 46-year-old woman with HER2-positive early breast cancer is started on adjuvant chemotherapy with trastuzumab. Which specific toxicity requires baseline assessment and serial monitoring throughout therapy?

• A Peripheral neuropathy assessed by nerve conduction studies
• B Pulmonary fibrosis assessed by diffusion capacity
• C Ototoxicity assessed by pure tone audiometry
• D Decline in left ventricular ejection fraction assessed by echocardiography ✓

Explanation

Trastuzumab inhibits HER2 signalling important for cardiac myocyte survival and causes a reversible decline in left ventricular ejection fraction. Baseline and serial echocardiographic assessment every few months during therapy is mandatory, and significant falls require holding or stopping the drug. Unlike anthracycline cardiotoxicity, the damage is generally not dose-cumulative and is often reversible. Neuropathy and ototoxicity belong to taxanes and platinum agents, and pulmonary fibrosis is associated with bleomycin.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

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