Herceptin (Trastuzumab)

Herceptin is used in clinical practice for several HER2‑positive malignancies, where it targets the HER2 receptor to improve outcomes.

• Treatment of HER2‑positive metastatic breast cancer, often with chemotherapy.
• Adjuvant therapy for HER2‑positive early‑stage breast cancer after surgery.
• Management of HER2‑positive gastric or gastroesophageal adenocarcinoma.
• Combined with taxane‑based chemotherapy in advanced disease settings.
• Neoadjuvant use before surgery to increase pathological response rates.
• Maintenance therapy following initial response in metastatic HER2‑positive disease.
• Combined with pertuzumab to provide dual HER2 blockade in selected regimens.

• Trastuzumab is a humanized IgG1 monoclonal antibody that binds with high affinity to the extracellular domain IV of the human epidermal growth factor receptor 2 (HER2). By occupying this site, it blocks ligand‑independent dimerization and downstream signaling through the PI3K/AKT and MAPK pathways. The bound antibody also recruits immune effector cells, leading to antibody‑dependent cellular cytotoxicity (ADCC) against HER2‑overexpressing tumor cells.

Herceptin may cause a range of adverse reactions, which are generally categorized as common or serious.

Common

• Infusion‑related reactions such as fever, chills, flushing, or nausea during or shortly after administration.
• Fatigue or generalized weakness that may affect daily activities.
• Diarrhea or abdominal discomfort, sometimes with mild cramping.
• Rash or mild skin irritation at the injection site, often presenting as redness or itching.

Serious

• Cardiac dysfunction, including reduced left ventricular ejection fraction, which may cause shortness of breath or edema.
• Severe allergic reactions (anaphylaxis) with respiratory distress, hypotension, or urticaria requiring immediate medical attention.
• Thrombocytopenia or neutropenia leading to increased risk of bleeding or infection, possibly necessitating treatment interruption.

When prescribing Herceptin, clinicians should consider several precautions to minimize risks and ensure safe use.

• Assess baseline cardiac function (e.g., left ventricular ejection fraction) before initiating therapy.
• Monitor cardiac function periodically during treatment, especially in patients with prior heart disease.
• Evaluate for pregnancy and advise appropriate contraception, as safety in pregnancy is not established.
• Screen for active infections, including hepatitis B, before starting therapy.
• Use caution in patients with known hypersensitivity to trastuzumab or any component of the formulation.
• Adjust or discontinue treatment if severe adverse reactions or significant laboratory abnormalities occur.

Herceptin may interact with other medicines, and certain combinations should be avoided or used with caution.

Avoid

• Concurrent use with other HER2‑targeted monoclonal antibodies not studied, due to potential additive toxicity.
• Live vaccines during treatment, because immunosuppression may reduce vaccine efficacy and increase infection risk.

Use with caution

• Anthracycline chemotherapy (e.g., doxorubicin) given sequentially, as combined cardiotoxicity may be increased.
• Cardiotoxic agents such as trastuzumab‑emtansine or pertuzumab, requiring close cardiac monitoring.
• Medications that prolong QT interval, which may exacerbate cardiac effects.
• Hormonal therapies (e.g., tamoxifen) may have overlapping metabolic pathways; monitor for potential interactions.