Herceptin (Trastuzumab)

Herceptin is employed in oncology to treat cancers that express high levels of the human epidermal growth factor receptor 2 (HER2).

• First‑line or adjuvant therapy for HER2‑positive early‑stage breast cancer.
• Combined with chemotherapy for HER2‑positive metastatic breast cancer.
• Treatment of HER2‑positive gastric or gastro‑esophageal adenocarcinoma in combination with chemotherapy.
• Used in neoadjuvant settings to shrink tumors before surgery in HER2‑positive breast cancer.
• May be continued as maintenance therapy after initial response in metastatic disease.

• Trastuzumab binds with high affinity to the extracellular domain IV of the HER2 receptor on tumor cells. This binding blocks ligand‑independent HER2 dimerization and downstream signaling pathways such as PI3K/AKT and MAPK, reducing cell proliferation. Additionally, the antibody flags the cancer cell for immune recognition, triggering antibody‑dependent cellular cytotoxicity (ADCC) that contributes to tumor cell elimination. It also interferes with HER2‑mediated angiogenic signals.

Patients receiving Herceptin may experience a range of adverse reactions, which are generally categorized by frequency and severity. These events can vary in intensity and may require medical evaluation.

Common

• Fever, chills, or flu‑like symptoms during infusion.
• Nausea, vomiting, or mild gastrointestinal upset.
• Fatigue or general weakness.
• Headache or dizziness.
• Rash or mild skin irritation.
• Elevated liver enzymes.

Serious

• Cardiac dysfunction, including decreased left ventricular ejection fraction.
• Severe infusion‑related reactions such as anaphylaxis or bronchospasm.
• Thrombocytopenia or neutropenia.
• Pulmonary toxicity, including interstitial pneumonitis.
• Renal impairment.
• Severe diarrhea.

Before initiating Herceptin therapy, clinicians assess several safety considerations to minimize risk and ensure appropriate monitoring.

• Baseline cardiac assessment (e.g., echocardiogram) is recommended because of potential cardiotoxicity.
• Monitor cardiac function periodically during treatment, especially in patients with pre‑existing heart disease.
• Evaluate for pregnancy; trastuzumab is contraindicated during pregnancy due to unknown fetal risk.
• Assess for active infections, as immunosuppression may increase susceptibility.
• Review concomitant medications that can affect cardiac output or cause hypersensitivity.
• Adjust dosing or discontinue if significant decline in left ventricular ejection fraction occurs.
• Provide pre‑medication (antihistamine and antipyretic) to reduce infusion‑related reactions when indicated.

Herceptin may interact with other agents, influencing safety or therapeutic effectiveness; awareness of these interactions guides clinical decisions.

Avoid

• Concurrent use with other HER2‑targeted monoclonal antibodies (e.g., pertuzumab) without established combination protocols.
• Live vaccines during treatment, due to potential immune suppression.

Use with caution

• Anthracycline chemotherapy (e.g., doxorubicin) because of additive cardiac toxicity.
• Concomitant cardiotoxic drugs such as trastuzumab emtansine or certain tyrosine kinase inhibitors.
• Medications that prolong QT interval, which may exacerbate cardiac monitoring challenges.
• Hormonal therapies that affect cardiac risk profile, requiring closer observation.