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Trastuzumab emtansine (Kadcyla)

Find out what trastuzumab emtansine (Kadcyla) is, how you have it and other important information about having trastuzumab emtansine.

Trastuzumab emtansine is pronounced trast-oo-zoo-mab em-tan-seen. It is a combination of the drug trastuzumab and a drug called emtansine. It is also known by its brand name, Kadcyla (pronounced cad-sigh-lah].

It is a treatment for HER2 positive breast cancer that has come back or spread to other parts of the body. You usually only have it if you have had treatment with trastuzumab (Herceptin) and a drug known as a taxane.

You may also have it as part of clinical trials for other types of cancer.

How it works

Trastuzumab is a type of targeted cancer drug (biological therapy) called monoclonal antibody. Emtansine is a cancer drug that becomes active once Kadcyla enters the cancer cell.

Some breast cancers have too much of a protein called human epidermal growth factor receptor 2 (HER2) on the surface of their cells. These are called HER2 positive cancers. HER2 makes the cells grow and divide. Trastuzumab attaches to the HER2 receptor. When this happens it allows the emtansine to go into the cancer cell. Inside the cell emtansine becomes active and kills the cancer cell.

How you have it

Trastuzumab emtansine is a clear fluid. You have it into your bloodstream (intravenously).

Drugs into your bloodstream

You have the treatment through a drip into your arm or hand. A nurse puts a small tube (a cannula) into one of your veins and connects the drip to it.

You might need a central line. This is a long plastic tube that gives the drugs into a large vein, either in your chest or through a vein in your arm. It stays in while you’re having treatment, which may be for a few months.

When you have it

You have trastuzumab emtansine every 3 weeks. You have the first treatment over 90 minutes. You might have the next treatments over 30 minutes if the first one went well. 

You continue to have treatment as long as it helps and the side effects aren't too bad.


You have blood tests before and during your treatment. They check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.

Side effects

Important information

Other medicines, foods and drink

Cancer drugs can interact with some other medicines and herbal products. Tell your doctor or pharmacist about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies.

Pregnancy and contraception

This drug may harm a baby developing in the womb. It is important not to become pregnant or father a child while you are having treatment with this drug and for at least 7 months afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.


Don’t breastfeed during this treatment and for 7 months afterwards. The drug may come through in the breast milk.


It is not known whether this treatment affects fertility in people. Talk to your doctor before starting treatment if you think you may want to have a baby in the future.

Treatment for other conditions

Always tell other doctors, nurses, pharmacists or dentists that you’re having this treatment if you need treatment for anything else, including teeth problems.


Don’t have immunisations with live vaccines while you’re having treatment and for up to 12 months afterwards. The length of time depends on the treatment you are having. Ask your doctor or pharmacist how long you should avoid live vaccinations.

In the UK, live vaccines include rubella, mumps, measles, BCG, yellow fever and the shingles vaccine (Zostavax).

You can:

  • have other vaccines, but they might not give you as much protection as usual
  • have the flu vaccine (as an injection)
  • be in contact with other people who have had live vaccines as injections

Avoid close contact with people who have recently had live vaccines taken by mouth (oral vaccines) such as oral polio or the typhoid vaccine.

This also includes the rotavirus vaccine given to babies. The virus is in the baby’s poo for up to 2 weeks and could make you ill. So avoid changing their nappies for 2 weeks after their vaccination if possible. Or wear disposable gloves and wash your hands well afterwards.

You should also avoid close contact with children who have had the flu vaccine nasal spray if your immune system is severely weakened. 

More information about this treatment

For further information about this treatment go to the electronic Medicines Compendium (eMC) website.

You can report any side effect you have to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

Information and help

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