Trastuzumab: Therapy Against HER2 Positive Breast Cancer

Trastuzumab is a highly important advance in the therapeutic options available for metastatic breast cancer. Its use is beneficial especially in HER2 positive patients.
Trastuzumab: Therapy Against HER2 Positive Breast Cancer

Last update: 12 May, 2021

Trastuzumab is the first targeted therapy against an oncogene for patients with HER2 positive breast cancer. An oncogene is a gene that has a high capacity for mutation or transformation that induces cancer formation in tissue.

At the same time, HER2 positive breast cancer refers to a type of neoplasm that has overexpressed receptors for this protein. HER2 proteins are receptors on breast cells produced by the HER2 gene, which are necessary in normal situations. These proteins allow breast cells to divide and repair themselves.

HER2 positive breast cancers account for 20-30% of breast tumors in humans. Experts associated this type of cancer with a poor prognosis, including reduced recurrence-free survival and overall survival.

Mechanism of action: How does trastuzumab exert its effect on the body?

An image of a breast with metastatic breast cancer.

This drug is a humanized monoclonal antibody. In other words, it’s a drug consisting of an antibody produced by a single type of immune system cell: B lymphocytes.

We say it’s humanized because it’s a combination of a human antibody with a small proportion of a monoclonal antibody from a mouse or rat. The animal portion of the antibody binds to the target antigen. At the same time, the human portion makes it less likely for the body’s immune system to destroy it.

In this sense, trastuzumab acts on the HER2 receptor of mammary cells by preventing cell proliferation of cells overexpressing this receptor. Finally, it causes the death of these cells. At the same time, it also triggers an antibody-controlled immune response against cells overexpressing the HER2 receptor.

Therapeutic indications for trastuzumab

Trastuzumab, as we already know, is indicated for the treatment of metastatic breast cancer whose tumors overexpress HER2 receptors. There are two ways to administer it.

Firstly, it can be administered alone – monotherapy. Doctors choose this regimen for patients who’ve already received at least two chemotherapy regimens for metastatic disease.

Previous chemotherapy must have included at least one anthracycline and one taxane, which are other anticancer drugs. To administer trastuzumab as monotherapy, patients who are also hormone-receptor-positive must have failed hormone therapy. That is, unless hormone therapy isn’t recommendable due to the patient’s medical condition.

Secondly, the administration of trastuzumab can go along with that of a taxane such as paclitaxel. Doctors opt for this option when patients haven’t received previous chemotherapy.

You may also be interested in reading: BRCA-1 and BRCA-2 Genes and Breast Cancer

Adverse reactions to trastuzumab

A woman caring for a woman with breast cancer.

Like all drugs on the market, trastuzumab isn’t exempt from producing a series of adverse effects. Adverse effects are all those undesirable and unintended events that you may expect to experience with treatment with a drug.

So, the most reported adverse reactions during clinical trials were perfusion-related symptoms. For example, fever and chills after the first dose. At the same time, approximately 10% of patients presented:

  • Abdominal and chest pain
  • Diarrhea, nausea, and vomiting
  • Pain in the joints and muscles
  • Skin rashes

There’s another series of adverse reactions that between 1 and 10% of patients have described. Some of them are:

  • Flu syndrome
  • Back pain
  • Vasodilatation
  • Tachycardia
  • Lack of appetite
  • Dry mouth
  • Anxiety
  • Taste alteration
  • Leukopenia


Trastuzumab has made a highly important contribution to the therapeutic options available for metastatic breast cancer. This drug provides a significant advantage in metastatic disease, especially in HER2 positive patients receiving concomitant treatment with paclitaxel.

Despite these advances, it’s essential to continue active research. Studies aim to evaluate drug combinations for chemotherapy, as well as improving the detection of HER2 proteins. A more specific detection would bring the benefit of proposing a more efficient treatment for patients who really need it.

It might interest you...
Palbociclib to Treat Breast Cancer
Step To HealthRead it in Step To Health
Palbociclib to Treat Breast Cancer

The commercialization of palbociclib has meant a great advance in health as it's used to treat breast cancer. Learn more in this article!

  • Romond, E. H., Perez, E. A., Bryant, J., Suman, V. J., Geyer, C. E., Davidson, N. E., … Wolmark, N. (2005). Trastuzumab plus adjuvant chemotherapy for operable HER2-positive breast cancer. New England Journal of Medicine.
  • Slamon, D. J., Leyland-Jones, B., Shak, S., Fuchs, H., Paton, V., Bajamonde, A., … Norton, L. (2001). Use of chemotherapy plus a monoclonal antibody against her2 for metastatic breast cancer that overexpresses HER2. New England Journal of Medicine.
  • Findlay, V. J., & Scholar, E. (2007). Trastuzumab. In xPharm: The Comprehensive Pharmacology Reference.