At the beginning of August, the Food and Drug Administration approved Trastuzumab Deruxtecan (Enhertu) for HER2-low breast cancer patients with unresectable tumors who developed recurrence within a short time of completing adjuvant chemotherapy, as well as for HER2-low breast cancer patients with metastatic disease who have received prior chemotherapy.
The HER2 protein regulates and controls the growth of cells. Over expression (excessiveness) of HER2 protein on breast cancer cells surface makes them grow and divide in an uncontrolled way, thereby promoting the cancer process.
The level of HER2 protein is elevated in about 20% of breast cancer patients. A large number of studies has shown that these patients might benefit from the addition of biological therapy, which specifically targets the HER2 protein, to the chemotherapy regimen already administrated.
Until now, breast cancer patients with HER2-low expression could not receive such treatment, due to the lake of scientific data suggesting its effectiveness among these patients.
The approval was based on results from a clinical trial in which 557 patients with unresectable or metastatic disease with HER2-low expression were enrolled. Patients were randomized to receive either Enhertu (study group) or chemotherapy (control group).
The study results point towards a significant lower risk of disease progression among those receiving Enhertu, compared to those receiving chemotherapy. In addition, a significantly lower death rate was observed among those receiving Enhertu, compared to those receiving chemotherapy.
Among the most common adverse events in patients receiving Enhertu in this trial were nausea, vomiting, constipation, diarrhea, alopecia and anemia. Enhertu requires careful monitoring as for all other anti-cancer drugs.
Based on the promising study results, the researchers believe that the efficacy seen in Enhertu reinforces the potential to establish a new standard of care for advanced breast cancer patients with HER2-low expression.
Since about half of all patients with breast cancer have tumors with HER2-low expression, farther investigation for the efficacy of biological therapies that target HER2 protein among these patients is warranted.