Research presented at the San Antonio Breast Cancer Symposium may result in a new standard of care for some people with HER2 positive, early stage breast cancer. Typically, patients treated with a combination of chemotherapy and Herceptin (trastuzumab) who still have some breast cancer remaining at the time of surgery are given more Herceptin afterward. They tend to have a higher rate of the cancer returning than people whose cancer was completed destroyed and have no remaining cancer after surgery. But the study showed they did better if they’re given Kadcyla (T-DM1), which is a newer drug, instead of Herceptin after surgery. The study was published December 5, 2018 in the New England Journal of Medicine.
Kadcyla is a combination of Herceptin and a chemo drug that work together to keep cancer cells from growing. It’s already approved by the US Food and Drug Administration to treat women with HER2 positive breast cancer that has metastacized (spread). HER2 is a protein on breast cells that help cancer grow when their levels are higher than normal. About 1 in 5 women with breast cancer have HER2 positive cancer. Drugs including Herceptin and Kadcyla target the HER2 protein.
The study involved 1,486 people with HER2 positive, early stage breast cancer treated with chemo and Herceptin, who had remaining breast cancer at surgery. They were randomly assigned to receive Kadcyla or Herceptin after surgery and were on the medication for about a year. The study was designed to measure disease-free survival, which is how long the patient stayed alive and cancer-free. After 3 years, the rate of disease-free survival was 88% in the Kadcyla group compared with 77% in the Herceptin group. More people in the Kadcyla group (18%) than the Herceptin group (2.1%) stopped the drug because of side effects, but the increase in side effects was expected from what is already known about Kadcyla.
In addition, when cancer did return, it was less likely to be at an advanced stage in patients taking Kadcyla. Metastatic cancer (cancer that has spread) came back in 10.5% of patients in the Kadcyla group vs. 15.9% in the Herceptin-only group.
Kadcyla showed significant benefits, enough so that the researchers say their findings will change standard treatment for patients like those in the study. However, it is also more likely to cause side effects including low blood platelet counts, nerve pain and numbness, and elevated liver enzymes.
The American Cancer Society medical and editorial content team
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Trastuzumab Emtansine for Residual Invasive HER2-Positive Breast Cancer. Published December 5, 2018 in the New England Journal of Medicine. First author Gunter von Minckwitz, MD, the German Breast Group, GBG Forschungs, Neu-Isenburg, Germany.
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