Trastuzumab (Herceptin®) - Therapeutic Drug Monitoring (TDM)

Trastuzumab is a humanised IgG1 monoclonal antibody produced by Chinese hamster ovary cells that binds to the human epidermal growth factor receptor 2 (HER2). 20-30% of primary breast cancers show overexpression of HER2. Trastuzumab inhibits proliferation of tumor cells that overexpress HER2. Additionally, trastuzumab is a potent mediator of antibody-dependent cell-mediated cytotoxicity (ADCC).

Clinical Use

Herceptin can only be used when the cancer has been shown to overexpress HER2.

In Europe, trastuzumab is indicated for treatment of:

  • early breast cancer (without metastases) after surgery, chemotherapy, and radiotherapy if applicable. It can also be used earlier in treatment, in combination with chemotherapy.
  • metastatic breast cancer, used on its own in patients in whom previous treatments have failed.
  • When used as an infusion into a vein, Herceptin can also be used for metastatic gastric (stomach) cancer, in combination with cisplatin and either capecitabine or 5-fluorouracil.

Testing trastuzumab concentration:

The assay is performed using Enzyme Linked Immunosorbent Assay (ELISA). The limit of quantification (LOQ) for trastuzumab in serum is 0.0002 µg/mL.

Testing trastuzumab anti-drug antibodies (ADA):

Not available.

Clinical Relevance

No response or loss of response of treatment with trastuzumab.

With level testing of biologics, efficacy of therapy can be improved, as treatment decisions may need to be adapted depending on the test results in conjunction with clinical responses to treatment.

Data and interpretation of trastuzumab serum levels are still very limited.

Personalized Medicine

Monitoring biologic levels in individual patients allows optimization of treatment efficacy by adjusting therapy depending on the specific response of the patient. When drug levels are decreased in a non-responder, this may reflect formation of inactivating antibodies directed to the biologic treatment. Immunogenicity testing identifies presence or absence of inactivating antibodies, which guides the next treatment decision – switch to other biological treatment, lowering of dose or intensify dosing. Reducing drug dosage in well-responding patients with relatively high drug levels cuts down cost. A personalized approach can improve therapy efficacy and quality of life.

Read more on the following pages:

Order of test: Print and complete the request form and send it together with the sample.

For further questions please contact us.

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