Herceptin (Trastuzumab)

Herceptin is indicated for several HER2‑positive malignancies, typically as part of a combination regimen prescribed by oncologists.

• HER2‑positive metastatic breast cancer
• HER2‑positive early breast cancer (adjuvant therapy)
• HER2‑positive gastric or gastro‑esophageal junction adenocarcinoma
• HER2‑positive metastatic gastric cancer

• Trastuzumab binds with high affinity to the extracellular domain IV of the human epidermal growth factor receptor‑2 (HER2) protein on the surface of tumor cells. This binding blocks ligand‑independent HER2 signaling, inhibits downstream pathways such as PI3K/AKT and MAPK, and flags the cell for immune‑mediated destruction through antibody‑dependent cellular cytotoxicity (ADCC), thereby reducing tumor proliferation and may also promote receptor internalization.

Adverse reactions to Herceptin vary in frequency and severity; they are reported in clinical studies and post‑marketing surveillance.

Common

• Infusion‑related reactions such as fever, chills, or nausea
• Fatigue or weakness
• Diarrhea or abdominal pain
• Rash or mild skin irritation

Serious

• Cardiac dysfunction or decreased left ventricular ejection fraction
• Severe infusion‑related anaphylaxis
• Pulmonary toxicity including interstitial pneumonitis

Herceptin requires careful monitoring and patient selection to minimize risks.

• Baseline and periodic cardiac assessment (e.g., echocardiogram) is recommended due to potential cardiotoxicity.
• Infusion should be administered by healthcare professionals experienced with monoclonal antibody therapies.
• Patients with known hypersensitivity to trastuzumab or any component of the formulation should avoid use.
• Caution is advised in patients with pre‑existing lung disease or recent respiratory infections.
• Pregnant or breastfeeding women should discuss potential risks with their physician.
• Concomitant use with other cardiotoxic agents may increase cardiac risk.

Herceptin may interact with other medications; clinicians should evaluate potential risks.

Avoid

• Concurrent use with anthracyclines (e.g., doxorubicin) due to heightened cardiotoxicity.
• Live vaccines during treatment, as immune modulation can affect vaccine efficacy.

Use with caution

• Other HER2‑targeted agents (e.g., pertuzumab) may increase cardiac monitoring requirements.
• Medications that prolong QT interval may compound cardiac effects.
• Drugs that affect hepatic metabolism are unlikely to alter trastuzumab levels but should still be reviewed.