Understand the background: That's why everyone is talking about HER2-low

The treatment with Enhertu in particular has made it relevant to distinguish between HER2-negative disease and HER2-low disease. Some of the very effective treatments, which have previously only been used for HER2-positive breast cancer patients, have been shown to be beneficial for HER2-low patients as well.

Around half of all women with breast cancer have a disease with a low HER2 expression, which is therefore called HER2-low. Previously, these women were categorized as HER2 negative.

We all have HER2 receptors on our cells. They tell the cells when to grow and when to stop growing. The normal cell has few receptors, whereas the cell that is HER2 positive has many receptors. If you are HER2-positive, the cells are overstimulated and can grow uncontrollably, which can lead to cancer.

When testing women with breast cancer for HER2, women whose tumors fall within the +3 category will be defined as HER2-positive. All tumors with a lower HER2 expression have so far been defined as HER2-negative.

The understanding of HER2 status changed

If you are among the 10-15 percent who are HER2-positive - and if you have a relapse of your disease after receiving treatment -, you can today be offered treatment with the cancer medicine Enhertu (trastuzumab deruxtecan, T-DXd), which is a so-called antibody drug conjugate.

Enhertu is a targeted drug that binds to the HER2 receptor. Enhertu was approved in Denmark in January this year.

However, a large international study called DESTINY-Breast04, which was presented in June 2022, has advanced the understanding of HER2 status. And from here it went strong. The study showed that women with metastatic breast cancer had an effect from the treatment with Enhertu, even though the pathological analyzes of their tumor showed that they had a low HER2 expression. Enhertu had a significant life-prolonging effect and fewer side effects compared to chemotherapy. This is the group that makes up the new category, and which is now defined as HER2-low.

Recommended in several countries
On the basis of the study, Enhertu was approved by the European Medicines Agency EMA for the treatment of HER2-low. Since then, the drug has been recommended in a number of European countries, including Norway, which has just approved it. But in Denmark, Enhertu is only approved for the group of breast cancer patients who are HER2-positive, while the new group (HER2-low), which makes up around half of all Danish women with breast cancer, cannot have the treatment financed by the state.

The price of Enhertu depends on body weight and the dose that is needed. Typically three to four doses are given per treatment every three weeks. This means that the cost of medicine alone amounts to a price of DKK 815,040 - DKK 1,086,720 annually.

Source: Onkologisk Tidsskrift