Herceptin (Trastuzumab)

Herceptin (trastuzumab) is indicated for the treatment of cancers that overexpress the HER2 protein. It is used in adult patients with confirmed HER2‑positive disease as part of a multimodal therapeutic regimen.

• HER2‑positive breast cancer, in combination with chemotherapy, as adjuvant, neoadjuvant, or metastatic therapy.
• HER2‑positive metastatic breast cancer after prior trastuzumab‑containing regimens.
• HER2‑positive gastric or gastro‑oesophageal junction adenocarcinoma, in combination with chemotherapy.
• HER2‑positive breast cancer in the adjuvant setting for patients with high‑risk disease.
• HER2‑positive breast cancer in the neoadjuvant setting to increase pathological complete response rates.

• Trastuzumab is a humanized IgG1 monoclonal antibody that binds with high affinity to the extracellular domain IV of the HER2 receptor. By blocking ligand‑independent dimerisation, it inhibits downstream signaling pathways such as PI3K/AKT and MAPK, reducing cell proliferation and survival. The antibody also recruits immune effector cells, mediating antibody‑dependent cellular cytotoxicity (ADCC) that contributes to tumor cell elimination in the tumor microenvironment.

Adverse reactions to Herceptin may vary in frequency and severity. The most frequently reported events are listed under common, while less frequent but potentially serious events are listed under serious.

Common

• Infusion‑related reactions (fever, chills, nausea, flushing).
• Fatigue or asthenia.
• Diarrhea or abdominal discomfort.

Serious

• Cardiac dysfunction, including reduced left ventricular ejection fraction or heart failure.
• Severe infusion reactions such as anaphylaxis or bronchospasm.
• Pulmonary toxicity, including interstitial pneumonitis.

Healthcare professionals should consider several precautions before initiating Herceptin therapy to minimize risks and monitor patient safety.

• Assess baseline cardiac function with echocardiography or MUGA scan and repeat periodically during treatment.
• Avoid use in patients with known hypersensitivity to trastuzumab or any component of the formulation.
• Use caution in patients with pre‑existing cardiac disease, hypertension, or arrhythmias.
• Monitor for signs of infusion‑related reactions and be prepared to manage anaphylaxis.
• Evaluate pregnancy status; trastuzumab is contraindicated during pregnancy due to potential fetal harm.
• Consider dose adjustments or discontinuation if significant cardiac decline is observed.

Herceptin may interact with other medicines, affecting its safety or efficacy. Known interactions are grouped below.

Avoid

• Concurrent use with anthracyclines (e.g., doxorubicin, epirubicin) due to increased risk of cardiotoxicity.
• Combination with other HER2‑targeted agents that have overlapping cardiac toxicity profiles.

Use with caution

• Concurrent administration of cardiotoxic chemotherapy (e.g., cyclophosphamide, paclitaxel) requires cardiac monitoring.
• Use with live vaccines is generally discouraged because of potential immune modulation.
• Concomitant use of drugs that prolong the QT interval may increase the risk of arrhythmias.
• Herbal supplements that affect immune function (e.g., echinacea) should be discussed with the prescriber.