For the first time, a drug that targets a protein that promotes breast cancer growth has been shown to be effective against tumors with very low levels of the protein, Carla K. Johnson reported for the Associated Press (AP).
Photo Insert: Enhertu manufacturing line
It’s not a cure. However, this latest advancement in targeted cancer therapy may open up new treatment possibilities for thousands of patients with advanced breast cancer. Breast cancers were previously classified as either HER2-positive (the cancer cells have more of the protein than normal) or HER2-negative.
According to doctors who reported the breakthrough on Sunday, "HER2-low" will become a new category for guiding breast cancer treatment.
Approximately half of patients with late-stage breast cancer who were previously classified as HER2-negative may actually be HER2-low and thus eligible for the drug. Enhertu is an antibody-chemotherapy combination administered intravenously.
It identifies and inhibits the HER2 protein on cancer cells while also delivering a potent cancer-killing chemical inside those cells. It is part of a relatively new class of drugs known as antibody-drug conjugates.
The drug was already approved for HER2-positive breast cancer, and the FDA granted it breakthrough status for this new group of patients in April.
The drug extended the time patients lived without their cancer progressing and improved survival compared to patients who received standard chemotherapy in the new study.
Enhertu was compared to standard chemo in a study of 500 patients with HER2-low breast cancer that had spread or could not be treated surgically. The drug slowed the progression of cancer for about 10 months, compared to about 5 1/2 months in the control group.
The drug increased survival time by about six months (from 17.5 months to 23.9 months).