(RxWiki News) In late February, the US Food and Drug Administration approved a new medication to treat HER2-positive breast cancer. The medication works by zeroing in on the HER2 proteins and then blasting them with a powerful chemotherapy agent.
A new study looked at which women might benefit most from this medication.
Kadcyla (trastuzumab emtansine, or T-DM1) was approved to treat metastatic (has spread) HER2-positive breast cancer in patients whose disease no longer responded to other therapies. The medication is marketed by Roche Holding AG.
After analyzing data from the EMILIA trial that led to T-DM1 approval, researchers found that the more HER2 molecules present, the more effective the medication was.
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HER2-positive breast cancer is one that tests positive for a protein called human epidermal growth factor receptor 2 (HER2). In about 20 percent of breast cancers, the cancer cells make too much of HER2 due to a gene mutation. HER2 promotes the growth of cancer cells. So, HER2-positive breast cancer is aggressive.
The new medicine T-DMI is part of a class of drugs called “antibody-drug conjugates.” These drugs combine an antibody (an immune soldier that attacks invaders) with a chemotherapy agent. The antibody identifies the HER2 proteins, and the chemotherapy kills them.
For this analysis, José Baselga, MD, PhD, physician-in-chief at Memorial Sloan-Kettering Cancer Center in New York, NY, and colleagues examined tissue samples from patients enrolled in the EMILIA trial. The participants were women with metastatic breast cancer which did not respond to standard therapies Herceptin (trastuzumab) or a type of chemotherapy called a taxane.
Researchers measured the levels of HER2 proteins in the tumors.
“Even though everyone enrolled in the clinical trial had breast cancer expressing elevated levels of HER2, we know that each person’s tumor has different molecular features,” said Dr. Baselga in a press release. “Even the degree to which HER2 expression is elevated differs from patient to patient.”
Patients with higher levels of HER2 benefited more from T-DM1 than women with lower levels of the protein. Women with higher levels of the protein lived about 34 months, while women with lower HER2 levels lived 26.5 months.
The researchers also looked at how the medication affected women with mutations in the PIK3CA gene. Women with this mutation typically have not lived as long as women without the altered gene.
In this study, PIK3CA mutations did not affect progression-free survival (period until the disease gets worse) in those treated with T-DM1.
“Our findings are an important step toward identifying the best therapy for individual patients with HER2-positive breast cancer,” said Dr. Baselga. “HER2-positive breast cancer is not a uniform disease; each patient is different. These data help us as we look to identify a panel of molecular features that we can use to make informed treatment decisions.”
Findings from this study were presented at the American Association for Cancer Research (AACR) Annual Meeting 2013. Before publication in a peer-reviewed journal, all research is considered preliminary.
Dr. Baselga has financial relationships with AstraZeneca, Bayer, Chugai, Constellation
Pharmaceuticals, Exelixis, Merck, Novartis, Onyx, Roche, Sanofi and Verastem.