Health SHARE 10 Oct 2025

Trastuzumab and HER2-Positive Breast Cancer

We look at trastuzumab and HER2-positive breast cancer in detail.

Trastuzumab is a breast cancer treatment that is often in the news. It has been referred to as a ‘breakthrough’ treatment due to its effectiveness in treating certain types of breast cancer, when combined with certain chemotherapy drugs.

Trastuzumab is effective in treating a type of breast cancer called HER2-positive breast cancer, allowing for more targeted chemotherapy delivery and improved patient outcomes.

What is trastuzumab?

Trastuzumab is a targeted therapy, also referred to as a biological therapy, for treating breast cancer. It is also sometimes used to treat other cancers, including stomach cancer and esophageal cancer.

Targeted therapies work by blocking the growth of cancer cells and stop them from spreading. They do this by interfering with the processes within the cancer cells that allow them to grow.

There is a protein on the surface of all breast cancer cells called HER2 which helps them to grow, repair and divide. If the HER2 gene is overactive, it makes too many HER2 proteins. This causes breast cancer cells to grow uncontrollably. This is a subtype of breast cancer, referred to as HER2-positive breast cancer.

Trastuzumab attaches to HER2 proteins and blocks the signals that tell cancer cells to grow. It also helps your immune system find and destroy these cells.

Trastuzumab is also available under its original brand name Herceptin and in several biosimilar forms. It may be given with another cancer drug, called pertuzumab, or on its own.

Who is given trastuzumab?

Trastuzumab is only beneficial to those with HER2-positive breast cancer. If you have high blood pressure or heart problems, it may not be suitable.

Trastuzumab may be given:

As a treatment for primary breast cancer: This is breast cancer that has not spread beyond the breast or lymph nodes under the arm.
Before surgery: It may be given before surgery, with chemotherapy, to slow down the growth of breast cancer, to stop it spreading or to shrink the breast cancer. This is called neoadjuvant therapy.
After surgery: It may be given after surgery to reduce the chance of the cancer spreading or returning. This is called adjuvant treatment.
To treat breast cancer that has returned or spread: It may be given to people whose breast cancer has returned to the breast area (local recurrence), whose breast cancer has spread to lymph nodes and tissues around the chest area (locally advanced) or whose breast cancer has spread to other parts of the body (secondary or metastatic breast cancer).

How is trastuzumab given?

Trastuzumab may be given as an injection under your skin or intravenously via a drip into your bloodstream.

For early breast cancer, locally advanced breast cancer and advanced breast cancer, trastuzumab is usually given once every three weeks. The duration of treatment will depend on many factors.

Like many HER2 targeted medications, trastuzumab is associated with potential side effects, including cardiac function abnormalities, headache, nausea, infusion reaction and diarrhea . Your doctor will discuss these with you in detail ahead of treatment.

How effective is trastuzumab?

Trastuzumab can be effective at reducing recurrence of HER2-positive breast cancer when combined with chemotherapy and improves patient outcomes.

The effectiveness of any cancer treatment will be affected by many things, including the type of cancer you have and individual factors.

Your doctor will discuss effectiveness, treatment plans, risks and benefits with you in detail before any treatment is given.