Herceptin (Trastuzumab)

Herceptin is used in adult patients whose tumors show overexpression of the human epidermal growth factor receptor 2 (HER2). It is approved for both early‑stage and advanced disease settings.

• HER2‑positive early breast cancer, typically in combination with chemotherapy or as adjuvant therapy.
• HER2‑positive metastatic breast cancer, often combined with taxane‑based chemotherapy.
• HER2‑positive gastric or gastro‑esophageal adenocarcinoma, used with chemotherapy regimens.
• HER2‑positive inflammatory breast cancer as part of a multimodal approach.
• HER2‑positive disease in patients who have completed neoadjuvant therapy and require continued HER2 blockade.

• Trastuzumab binds with high affinity to the extracellular domain IV of the HER2 receptor on tumor cells. This binding blocks ligand‑independent HER2 dimerization, inhibits downstream signaling pathways such as PI3K/AKT and MAPK, and reduces cellular proliferation. In addition, the antibody flags the cancer cell for immune recognition, promoting antibody‑dependent cellular cytotoxicity (ADCC) by natural killer cells. It also may enhance the effect of concurrent chemotherapeutic agents.

Like other monoclonal antibodies, Herceptin can cause a range of adverse reactions, from mild infusion‑related symptoms to rare but serious events.

Common

• Fever, chills, or flu‑like symptoms during or shortly after injection.
• Nausea, vomiting, or mild gastrointestinal upset.
• Injection‑site pain, erythema, or swelling.
• Fatigue or headache.

Serious

• Cardiac dysfunction, including reduced left ventricular ejection fraction.
• Severe allergic reactions such as anaphylaxis or angioedema.
• Thromboembolic events, including deep vein thrombosis or pulmonary embolism.

Herceptin requires careful monitoring because certain conditions can increase the risk of adverse outcomes or affect treatment efficacy.

• Assess baseline cardiac function (e.g., echocardiogram) before initiating therapy and periodically during treatment.
• Avoid use in patients with known hypersensitivity to trastuzumab or any component of the formulation.
• Use with caution in individuals with pre‑existing cardiac disease or uncontrolled hypertension.
• Monitor for signs of infection, especially during concurrent chemotherapy.
• Adjust or discontinue therapy if significant decline in left ventricular ejection fraction occurs.
• Counsel women of childbearing potential about the risks of fetal harm and advise effective contraception.

Herceptin may interact with other medications, influencing its safety profile or therapeutic effect.

Avoid

• Concurrent use with anthracycline chemotherapy (e.g., doxorubicin) due to increased risk of cardiotoxicity.
• Live vaccines during treatment, because immune modulation can reduce vaccine efficacy and increase infection risk.

Use with caution

• Other HER2‑targeted agents (e.g., pertuzumab, lapatinib) as combined therapy may heighten cardiac monitoring needs.
• Medications that prolong QT interval, which could compound cardiac effects.
• Hormonal therapies that affect cardiac function, requiring closer cardiac assessment.