Adding Tykerb to Herceptin Helps if Metastatic Breast Cancer Grows

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A study found that women diagnosed with HER2-positive metastatic breast cancer that either came back or progressed while getting Herceptin (chemical name: tastuzumab) benefited from adding Tykerb (chemical name: lapatanib) to the treatment plan instead of switching from Herceptin to Tykerb.

Both Herceptin and Tykerb are targeted therapy medicines.

There were almost 300 women in the study. After the HER2-positive metastatic breast cancer came back during Herceptin treatment, about half the women continued to get Herceptin AND had Tykerb added to their treatment plans. The other half stopped getting Herceptin and switched to Tykerb.

Six months later:

  • 28% of the cancers treated with both Herceptin and Tykerb didn't grow, compared to 13% of the cancers treated with only Tykerb.
  • Nearly 25% of the women who got both Herceptin and Tykerb benefited in some way from the treatment, compared to about 12% of the women who switched to Tykerb. The women were considered to benefit if the cancer didn't grow or went into complete or partial remission.
  • 80% of the women who got both Herceptin and Tykerb were alive, compared to 70% of the women who switched to Tykerb.

A year after the change in their treatment plans, 45% of the women treated with both Herceptin and Tykerb were alive, compared to 36% of the women who switched to Tykerb.

Both Herceptin and Tykerb work by blocking the ability of the HER-2/neu protein to make HER2-positive breast cancer cells grow. Herceptin and Tykerb do this in different ways. Herceptin blocks the protein on the cancer cell's surface. Tykerb blocks the protein inside the cell.

Tykerb, in combination with the chemotherapy medicine Xeloda (chemical name: capecitabine), is approved by the U.S. Food and Drug Administration to treat HER2-positive, metastatic breast cancer that has stopped responding to Herceptin. But rather than stopping Herceptin and switching to Tykerb when metastatic breast cancer comes back or progresses, many doctors have been adding Tykerb to the treatment plan while continuing Herceptin.

Even though Tykerb isn't approved to be used in combination with Herceptin, the results of this study suggest that this approach might be better than stopping Herceptin and switching to Tykerb. The researchers think that blocking the effect of the HER2/neu protein both outside and inside the cancer cell at the same time might be better than blocking the protein in only one place. This approach is known as "total HER2 blockade."

Herceptin is given intravenously. Herceptin can cause flu-like side effects such as fever, chills, muscle aches, or nausea. These side effects generally become less severe after the first treatment. Herceptin can sometimes cause heart damage and in some cases the heart damage can be life-threatening.

Tykerb is a pill taken by mouth. Tykerb doesn't seem to cause the serious heart problems associated with Herceptin. The most common side effects from Tykerb when given in combination with Xeloda are diarrhea, redness and tingling in the hands and feet, and a rash. These side effects usually aren't severe. Other side effects can include stomach upset, vomiting, and fatigue.

In this study, the most common side effect was diarrhea. About 48% of the women treated with Tykerb alone had diarrhea; 60% of the women treated with Herceptin and Tykerb had diarrhea. One woman did die from a heart problem, but the heart problem wasn't directly related to the Herceptin or Tykerb treatment.

If you're being treated with Herceptin for HER2-positive metastatic breast cancer, you might want to talk to your doctor about the results of this research. Together you and your doctor can decide whether adding Tykerb to your treatment plan might make sense for you if the cancer stops responding to Herceptin alone.

Visit the Breastcancer.org Targeted Therapies section to learn more about Herceptin and Tykerb.

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