trastuzumab at a glance
Medicine class
HER2-targeted humanised monoclonal antibody
Main uses
HER2-positive early or metastatic breast cancer; the intravenous formulation also has a licensed role in selected metastatic gastric or gastro-oesophageal junction cancer.
How it is given
Into a vein as an infusion or, for breast cancer, under the skin of the thigh.
Before treatment
A validated tumour test must confirm HER2 overexpression or gene amplification.
What is trastuzumab used for?
Selected UK products are licensed for adults whose cancer meets specified HER2-testing criteria.
Early HER2-positive breast cancer, including specified treatment before or after surgery.
HER2-positive metastatic breast cancer, alone or with specified anti-cancer treatments depending on previous therapy and tumour characteristics.
The intravenous formulation, with specified chemotherapy, for previously untreated HER2-positive metastatic adenocarcinoma of the stomach or gastro-oesophageal junction.
The selected subcutaneous formulation is licensed for breast cancer, not gastric cancer.
How does trastuzumab work?
Trastuzumab binds to HER2 on cancer cells. This reduces HER2-driven growth signalling and helps immune cells recognise and attack HER2-overexpressing cells.
trastuzumab preparations and strengths
Solution for infusion
Route: Intravenous
Strengths: 150 mg, 420 mg
Injection
Route: Parenteral
Strengths: 600 mg
How to take trastuzumab
Treatment is organised by a specialist cancer team. The intravenous product is prepared and given as an infusion. The subcutaneous product is injected into the thigh and must never be given into a vein.
Check the product and route carefully: formulations and trastuzumab-containing antibody–drug conjugates are not interchangeable.
For subcutaneous administration, alternate thighs and avoid red, bruised, tender, hard or damaged skin.
Other subcutaneous medicines should preferably be injected at a different site.
Food does not affect administration because trastuzumab is not taken by mouth.
trastuzumab side effects
Common or expected effects
- Administration-related symptoms, including fever, chills, headache, nausea, rash or breathlessness
- Tiredness, weakness or flu-like symptoms
- Diarrhoea, vomiting or abdominal discomfort
- Headache or dizziness
- Muscle or joint pain
- Rash or other skin symptoms; the subcutaneous product can also cause injection-site redness, itching, swelling or pain
- Infections and blood-count changes, particularly when combined with chemotherapy
Get urgent medical advice
- Severe allergic or administration-related reaction, including wheezing, swelling, low blood pressure or collapse
- Heart dysfunction or heart failure, which may cause new breathlessness, worsening cough, ankle swelling, palpitations or unusual fatigue
- Severe lung inflammation or other pulmonary reaction causing new or worsening cough, breathlessness, low oxygen levels or fever
- Serious infection, especially with fever, shivering or rapidly worsening illness
trastuzumab in pregnancy
Trastuzumab is usually avoided during pregnancy unless specialists judge that maternal benefit outweighs fetal risk. Later-pregnancy exposure has been associated with reduced amniotic fluid and impaired fetal kidney function, sometimes causing serious lung complications. Effective contraception is advised during treatment and for seven months afterwards. Contact the oncology team promptly if pregnancy occurs.
trastuzumab while breastfeeding
Selected UK product information advises against breastfeeding during treatment and for seven months afterwards because transfer into human milk and risk to the infant are uncertain. Discuss feeding plans with the oncology and maternity teams.
trastuzumab interactions
Formal interaction studies are limited. The cancer team should review all current and planned treatments, including recently stopped medicines.
Doxorubicin, epirubicin and other anthracyclines
Combining or closely sequencing these medicines can increase cardiac risk; specialist planning and cardiac monitoring are required.
Taxanes
Cardiac and pulmonary adverse effects may be more likely in some treatment settings, requiring close monitoring of symptoms and cardiac function.
Gemcitabine, vinorelbine and radiation therapy
These may add to the risk of interstitial lung disease or other pulmonary toxicity.
Common questions about trastuzumab
Answers are fully visible for fast scanning and source review.
Is trastuzumab chemotherapy?
No. It is a targeted biological treatment—a monoclonal antibody against HER2—although it is often given alongside chemotherapy or other cancer treatments.
Why is HER2 testing needed before trastuzumab?
Trastuzumab targets HER2, so treatment is intended only when a validated tumour test confirms HER2 overexpression or gene amplification.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.