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Experimental Pyrotinib and Xeloda Regimen Better Than Tykerb and Xeloda for Metastatic HER2-Positive Breast Cancer

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The experimental anti-HER2 medicine pyrotinib plus the chemotherapy medicine Xeloda (chemical name: capecitabine) offered better progression-free survival than the anti-HER2 medicine Tykerb (chemical name: lapatinib) plus Xeloda for people diagnosed with metastatic HER2-positive breast cancer who had previously been treated with Herceptin (chemical name: trastuzumab) and chemotherapy, according to a study.

The research is part of the virtual program for the 2020 American Society of Clinical Oncology Annual Meeting. Read the abstract of “Pyrotinib or lapatinib plus capecitabine for HER2+ metastatic breast cancer (PHOEBE): A randomized phase III trial.”

Metastatic breast cancer is breast cancer that has spread to parts of the body away from the breast, such as the bones or liver.

Progression-free survival is how long a person lives without the breast cancer growing.

About pyrotinib

Pyrotinib is a tyrosine kinase inhibitor. Tyrosine kinases are enzymes that help control how cells grow and divide, among other functions. If the enzyme is too active or if a cell has too much of the enzyme, it can make cells grow uncontrollably. Pyrotinib blocks specific areas of the HER2 gene in HER2-positive cancer cells, which stops the cells from growing and spreading.

Pyrotinib is a pill taken by mouth.

Tykerb and Xeloda are also pills taken by mouth.

About the study

This analysis of the PHOEBE trial included 266 people diagnosed with metastatic HER2-positive breast cancer who had been previously treated with Herceptin and chemotherapy, either for metastatic breast cancer or for earlier-stage disease.

The people were randomly assigned to one of two treatment groups:

  • 134 people were treated with pyrotinib and Xeloda
  • 132 people were treated with Tykerb and Xeloda

Most of the people in the study either had no prior chemotherapy for metastatic disease or had received one earlier chemotherapy regimen:

  • 42.5% of the people treated with pyrotinib and Xeloda and 34.8% of people treated with Tykerb and Xeloda had no prior chemotherapy for metastatic disease
  • 41.8% of people treated with pyrotinib and Xeloda and 49.2% of people treated with Tykerb and Xeloda had been treated with one prior chemotherapy regimen for metastatic disease
  • 15.7% of people treated with pyrotinib and Xeloda and 15.9% of people treated with Tykerb and Xeloda had been treated with two prior chemotherapy regimens for metastatic disease

At the time of this interim analysis, progression-free survival was:

  • 12.5 months for people treated with pyrotinib and Xeloda
  • 6.8 months for people treated with Tykerb and Xeloda

This difference was statistically significant, which means that it was likely because of the difference in treatment and not just due to chance.

When the researchers looked at people in the study with HER2-positive metastatic disease that was resistant to Herceptin, they found that pyrotinib also improved progression-free survival among this group. For people with Herceptin-resistant disease, progression-free survival was:

  • 12.5 months for people treated with pyrotinib and Xeloda
  • 6.9 months for people treated with Tykerb and Xeloda

The researchers also noted that 70% of people treated with pyrotinib and Xeloda continue to respond to the medicine, compared to 48.5% of people treated with Tykerb and Xeloda.

Pyrotinib side effects

The most common side effects seen in people treated with pyrotinib and Xeloda were:

  • diarrhea, which was sometimes severe
  • hand-foot syndrome

In earlier studies, other side effects caused by pyrotinib and Xeloda included:

  • vomiting
  • nausea
  • mouth sores
  • loss of appetite

What this means for you

The results of this study are encouraging, but it’s important to know that pyrotinib is not approved in the United States to treat breast cancer.

If you’ve been diagnosed with metastatic HER2-positive breast cancer, were previously treated with Herceptin and chemotherapy, and are considering treatments for the metastatic disease, you may want to talk to your doctor about this study. While the PHOEBE trial is no longer accepting patients, there are other ongoing studies on pyrotinib.

Together, you and your doctor can decide if enrolling in a clinical trial studying pyrotinib is right for you.

For more information on participating in a study, including the benefits and risks, visit the Breastcancer.org Clinical Trials pages.

Written by: Jamie DePolo, senior editor

Reviewed by: Brian Wojciechowski, M.D., medical adviser


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