Herceptin® (trastuzumab) belongs to a new group of anti-cancer drugs called monoclonal antibodies.

It only works in women whose cancer has high levels of the HER2 protein (HER2 positive). Between 1 in 4 to 1 in 5 women with breast cancer have high HER2 levels.

Herceptin® may be used to treat women whose breast cancer has come back or spread to other parts of the body (secondary breast cancer). It may also be given to women with early breast cancer, as part of their initial treatment. It may be given on its own, or together with certain chemotherapy drugs.

Herceptin® works by interfering with one of the ways in which breast cancer cells divide and grow.

Some breast cancer cells are stimulated to multiply when a protein produced naturally in the body (human epidermal growth factor) attaches itself to a protein (HER2) on the surface of the breast cancer cells.

Herceptin® attaches itself to the HER2 protein, blocking the message to cancer cells to divide and grow. Herceptin® also stimulates the body's immune system to help destroy the cancer cells.  

Herceptin® is given through a drip into a vein. It can be given as an outpatient. The first dose is given slowly, over about an hour and a half. Subsequent doses usually take 30 minutes to give. 

Side effects are usually mild. The commonest problem is temporary flu-like symptoms (fever and chills) shortly after the drug is given. Less often (in about 2 to 4 women in every 100 given the drug in studies) Herceptin®can cause heart problems. The risk of this seems to be greater in women with previous heart problems and when the drug is given with certain chemotherapy drugs such as doxorubicin.

The National Institute for Clinical Excellence (NICE) have issued guidance on the use of Herceptin®.