The short answer
Herceptin (Trastuzumab) is a targeted therapy called a monoclonal antibody. It attaches to a protein called HER2 that some cancers have in large amounts, blocking a growth signal and flagging those cells for the immune system. It is used to help treat HER2-positive breast cancer and some HER2-positive stomach cancers, and is usually given as an IV infusion (or an under-the-skin injection). Like all cancer medicines it can cause side effects; this page explains the common ones and the warning signs to report. It is educational only and not a substitute for your care team's advice.
Herceptin is the brand name; its generic name is trastuzumab.
It is a targeted therapy called a monoclonal antibody — it attaches to a protein called HER2 that some cancers have in large amounts, blocking a growth signal and flagging those cells for the immune system.
It is used to help treat HER2-positive breast cancer and some HER2-positive stomach cancers.
It is usually given as an IV infusion (or an under-the-skin injection).
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The full explanation.
What it is
Herceptin (Trastuzumab) is a cancer medicine. It is a type of targeted therapy called a monoclonal antibody. In plain terms, it attaches to a protein called HER2 that some cancers have in large amounts, blocking a growth signal and flagging those cells for the immune system. You may see it called by its brand name, Herceptin, or by its generic name, trastuzumab. This page is a general explainer based on the National Cancer Institute's drug information; it does not replace the specific instructions your own care team gives you.
What cancers it treats
According to the National Cancer Institute, trastuzumab is approved to help treat HER2-positive breast cancer and some HER2-positive stomach cancers. Whether it is the right choice for a particular person depends on the cancer type, its stage, test results such as biomarkers, and other treatments already tried. Your oncology team can explain why it was chosen for your situation.
How it's given
As an IV infusion (or an under-the-skin injection). It is given as an intravenous (IV) infusion — a slow drip into a vein — at a clinic or hospital, usually repeated on a schedule of cycles with rest periods in between. How much, how often, and for how long vary from person to person, so follow the exact schedule your care team gives you. If you miss an appointment or a dose, ask your team what to do rather than changing anything yourself.
Common side effects
Not everyone gets the same side effects, and some people have only mild ones. With trastuzumab, commonly reported effects include fever or chills with the first infusions, tiredness, headache, nausea, and diarrhea. Many of these can be eased with supportive care. Tell your care team if you notice anything new, if a side effect is getting worse, or if it is making everyday life hard — they can often help, and knowing early usually makes problems easier to manage. Side effects do not tell you whether the medicine is working.
Serious warning signs
Some problems need prompt attention. Contact your care team right away (or use the emergency number they give you) if you notice a fever or other signs of infection, severe or watery diarrhea, new shortness of breath or swelling, and unusual bruising or bleeding. This is not a complete list, and it cannot tell you whether your own situation is an emergency — that is exactly why your team gives you personal instructions and a number to call. When in doubt, it is always reasonable to check in with them.
The bottom line
Herceptin (Trastuzumab) is one of many tools used in cancer care. Understanding what it is, how it is given, and what to watch for can make treatment feel less overwhelming and help you speak up early about side effects. Keep a simple list of anything you notice, bring your questions to appointments, and remember that your care team — not a website — is the right source for decisions about your treatment.
Words to know
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Common questions
▸What is Herceptin?
Herceptin (Trastuzumab) is a targeted therapy called a monoclonal antibody. It attaches to a protein called HER2 that some cancers have in large amounts, blocking a growth signal and flagging those cells for the immune system. It is used to help treat HER2-positive breast cancer and some HER2-positive stomach cancers.
▸How is Herceptin given?
It is usually given as an IV infusion (or an under-the-skin injection). It is given as an intravenous (IV) infusion — a slow drip into a vein — at a clinic or hospital, usually repeated on a schedule of cycles with rest periods in between. The exact schedule is set by your care team.
▸What are the common side effects of Herceptin?
Commonly reported side effects include fever or chills with the first infusions, tiredness, headache, nausea, and diarrhea. Not everyone gets them, and many can be managed. Tell your care team about anything new or worsening.
▸Does Herceptin cure cancer?
That depends on the person, the cancer type, and its stage. For some people a medicine like this can control cancer for a long time or be part of a curative plan; for others the goal is to slow the cancer or ease symptoms. Your care team can explain the goal in your situation.
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