The tamoxifen test from Dr. Seibt Genomics

Is a tamoxifen treatment planned after your surgical breast cancer therapy? Learn more.

Tamoxifen is used after surgical breast cancer therapy to treat any existing, invisible metastases and to prevent relapse.

Tamoxifen is a substance that must first be transformed by enzymes before it can act in the body. If a patient has altered enzymes, tamoxifen can no longer be transformed as expected. This will mean that the tamoxifen will not work as it should do.

[Translate to English:] Brustkrebspatientinnen

Learn more about our Dr. Seibt Genomics tamoxifen test and how it is being applied. We will explain which types of metabolization exist, i.e. what effect a drug delivered to the body can have and how tamoxifen is processed for it to work. As a result, you will find out whether and how your therapy can become even safer.

The tamoxifen test from Dr. Seibt Genomics can provide certainty

The easy-to-use test by Dr. Seibt Genomics analyzes the metabolism of tamoxifen to endoxifen and thus the activity of the enzyme CYP2D6. This will tell you whether you are able to convert tamoxifen into the desirably effective endoxifen.

What do I need to do I want you to carry out an analysis?

The effort you have to invest in the test is manageable:

  • After completing the interview with your gynecologist, you will then fill out the order form together. The signatures of you and your doctor on the form are particularly important.
  • You can then test yourself at home or in the doctor’s practice since it only involves using a cheek swab. Please note that you should NOT eat, drink, smoke or chew gum for 60 minutes prior to cheek swabbing. Even brushing your teeth or using mouth washes are taboo.
  • Then send the sample tube to us together with the completed order in the prepared envelope.
  • You shall then receive an invoice for €390.00. Once the amount has been paid, we will start with the analysis.

We will send the result by post to your doctor so that you can discuss the resulting treatment options with him/her at your next appointment.

You can purchase our Dr. Seibt Genomics tamoxifen test in our online store (available soon) or contact us to order the test kit.

The different ways tamoxifen is metabolized

  • Slow metabolizers
    Approximately 5% of patients have two non-functional alleles of the CYP2D6 gene. In these individuals no protein is formed and the metabolism is extremely slow. At the standard dose, the efficacy of tamoxifen is not sufficient.
  • Intermediate metabolizers
    Approximately 39% of patients possess a restrictively functional allele. In these individuals the tamoxifen is metabolized with reduced activity. The effectiveness is restricted.
  • Extensive (“normal”) metabolizers
    Approximately 52% of patients have one or two fully functional alleles. Tamoxifen is converted into endoxifen in the required quantity.
  • Excessively rapid metabolizers
    Approximately 4% of patients have three or more copies of functional genes due to gene multiplication. They transform tamoxifen so rapidly that the standard dose may not be sufficient for the dosage interval. Due to activity spikes more side effects result.

As a result, half of all patients can not convert tamoxifen as would be desired.

The metabolism of tamoxifen

[Translate to English:] Der Stoffwechselweg von Tamoxifen

As the graph illustrates, tamoxifen is metabolized in the body via two different routes to endoxifen. The enzyme CYP2D6 is key to this transformation. CYP2D6 is, however, subject to significant genetic variations that impact on its activity. This can be seen in the different types of metabolization. If a patient has altered enzymes, tamoxifen can no longer be converted as expected. This will mean that the tamoxifen will not work as it should do.

Source: Dezentjé VO et al.; CYP2D6 genotype- and endoxifen-guided tamoxifen dose escalation increases endoxifen serum concentrations without increasing side effects. Breast Cancer Res Treat., 2015 Oct, 153 (3), 583-90

Your test results

The result of the analysis will be provided to your doctor within two weeks of the invoice being paid. You can then decide together whether ...

  • You should continue taking tamoxifen as before
  • You should change the dosage of tamoxifen
  • A change to an alternative substance is recommended

For you and your doctor we have compiled additional information for the possible continuation of your therapy in a PDF. We would be delighted if this test will result in your therapy becoming even safer.

The tamoxifen analysis can be ordered directly in our online store (available soon) or contact us to order the test kit.. If you have any questions, we would be happy to advise you personally - our contact details and a contact form can be found here.

Jump to top