• Assess for infusion-related symptoms (chills, fever, nausea, vomiting, pain [in some cases at tumor sites], headache, dizziness, dyspnea, hypotension, rash, and asthenia) following initial infusion. Severe reactions (bronchospasm, anaphylaxis, angioedema, hypoxia, severe hypotension) may occur during or immediately following the initial infusion. May be treated with epinephrine, corticosteroids, diphenhydramine, bronchodilators, and oxygen. Discontinue if dyspnea or severe hypotension occurs and discontinue permanently if severe reaction occurs.

• Assess for signs and symptoms of HF (dyspnea, increased cough, paroxysmal nocturnal dyspnea, peripheral edema, S₃ gallop, reduced ejection fraction) prior to and frequently during therapy. Baseline cardiac assessment of history, physical exam, and left ventricular ejection fraction (LVEF) with ECG or multiple gated acquisition (MUGA) scan. Monitor LVEF every 3 mo and at completion of therapy, every 6 mo for 2 yr. Withhold trastuzumab for ≥16% absolute decrease in LVEF from pre-treatment values or an LVEF value below institutional limits of normal and ≥10% absolute decrease in LVEF from pretreatment values. Repeat LVEF measures every 4 wk if dose is withheld. HF associated with trastuzumab may be severe, resulting in cardiac failure, death, and stroke. Trastuzumab should be discontinued upon the development of significant HF.

• Monitor patient for signs of pulmonary hypersensitivity reactions (dyspnea, pulmonary infiltrates, pleural effusion, noncardiogenic pulmonary edema, pulmonary insufficiency, hypoxia, acute respiratory distress syndrome). Patients with symptomatic pulmonary disease or extensive lung tumor involvement are at increased risk. Infusion should be discontinued if severe symptoms occur.

• HER2 protein overexpression is used to determine whether treatment with trastuzumab is indicated. HER2 protein overexpression is detected by HercepTest™ (IHC assay) and PathVysion™ (FISH assay).

» May cause anemia and leukopenia.