New drug doubles survival in metastatic breast cancer

Scientists from the Hospital Clínic-IDIBAPS, from the Catalan Institute of Oncology (ICO) and the Vall d'Hebron Institute of Oncology (VHIO) have participated in an international trial that has demonstrated the effectiveness of a new drug that doubles survival in patients with cancer metastatic breast cancer with low HER2 expression.

The new treatment, trastuzumab deruxtecan, manages to double survival without disease progression in patients with this type of tumor compared to standard treatments.

Oncologists from the Hospital Clínic-Idibaps participated in the research, published in the 'New England Journal of Medicine (NEJM)'. Aleix Prat and María Vidal, the oncologist at the Vall d'Hebron Hospital Cristina Saura, and the ICO oncologist Miguel Gil.

The results will be presented this Sunday during the plenary session of the American Society of Clinical Oncology (ASCO) congress.

Breast cancer It is the most common tumor in women worldwide, It affects 2,3 million people and kills 571.000 each year.

Levels of HER2, a protein found on the outside of the tumor cells, are routinely determined to decide the appropriate treatment strategy for breast cancer.

In the case of HER2-negative metastatic tumors, it has been seen that 55% do not have amplification of the HER2 gene (therefore, until now they are considered HER2-negative) but 70% of these express low levels of the HER2 protein ( HER2-low).

These HER2-low tumors are a very heterogeneous group that includes two other subtypes depending on whether or not the tumor cells express hormone receptors (HR): RH positive or RH negative.

Until now, patients with HER2-negative tumors did not benefit from anti-HER2 treatments such as trastuzumab, an antibody that has changed the evolution of HER2-positive breast cancer," he explained. Aleix Prat.

Now, thanks to this new immunoconjugate drug, which combines 7-8 molecules of a very powerful chemotherapy with the antibody trastuzumab, the survival of patients is prolonged," he added.

The new drug trastuzumab deruxtecan It combines a monoclonal antibody (trastuzumab) with a chemotherapy drug (deruxtecan) and has recently been approved to treat HER2+ metastatic breast cancer by the United States Medicines Agency (FDA) and Europe (EMA).

Now, this drug can also target tumor cells that express low levels of HER2 and transport the cytotoxic load to these tumor cells but also to neighboring cells without HER2 expression, an effect known as 'bystander'.

"One of the current challenges will be to ensure that HER2 levels are adequately looked at because until now it was not important, but now it is very important, and previous studies show great discordance between pathologists to identify low levels of HER2," María warned. Vidal.

The trial has evaluated the use of this drug in patients with HER2-low breast cancer who had received one or two previous chemotherapy treatments in addition to hormonal treatment.

557 patients participated in the trial, of which about 90% had an HR-positive tumor and 10% had an HR-negative tumor.

Progression-free survival was about 10 months when trastuzumab deruxtecan was used and 5,1 months with standard chemotherapy.

The average survival was 23,4 months compared to nearly 17 months in the same comparison.

"The results obtained are statistically significants, clinically very relevant and with very manageable adverse effects. This treatment will soon become a standard, and we hope that it will not take long to be incorporated into the public system once it is approved by the European Medicines Agency and the Spanish Agency for Medicines and Health Products," concluded Miguel Gil.