Experimental Combo Shows Promise for Treating Metastatic HER2-Positive Cancer

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A small, very early research study found that some women diagnosed with HER2-positive, metastatic breast cancer that had stopped responding to many other treatments, including Herceptin (chemical name: trastuzumab), responded to an experimental combination of Herceptin and Afinitor (chemical name: everolimus). The results were presented at the 2010 American Society of Clinical Oncology (ASCO) annual meeting.

Herceptin is used to treat advanced-stage, HER2-positive breast cancers and to lower the risk of recurrence of early-stage, HER2-positive breast cancer with a high risk of recurrence. HER2-positive cancers make too much of the HER2 protein. The HER2 protein sits on the surface of cancer cells and receives signals that tell the cancer to grow and spread. About 1 out of every 4 breast cancers is HER2-positive. Herceptin works by attaching to the HER2 protein and blocking it from receiving growth signals.

Afinitor is a targeted therapy medicine approved by the U.S. Food and Drug Administration to treat advanced-stage kidney cancer. It's being studied as a treatment for other cancers, including breast cancer.

Afinitor is an mTOR (mammalian target of rapamycin) inhibitor. mTOR is a type of protein called a kinase. Kinases help all cells (both normal and cancer cells) get the energy they need. When kinases don't act normally or are overactive they help certain breast cancers grow. Herceptin treats breast cancer by interfering with abnormal kinase activity linked to the HER2 protein. mTOR inhibitors work by interfering with the mTOR kinase.

This small, phase I/II study, looked at 47 women diagnosed with metastatic, HER2-positive breast cancer that had stopped responding to many other treatments, including Herceptin. Phase I/II studies help figure out the best dose of a new treatment that can be used safely without serious side effects. Phase I/II studies also help researchers figure out if a larger study involving more people makes sense.

The women were treated with a combination of Herceptin and Afinitor. Though the cancers had stopped responding to Herceptin alone, the researchers though that adding Afinitor might treat the cancer as well as make the cancer cells again start responding to Herceptin.

  • 7 women (15%) had the cancer shrink because of the Herceptin-Afinitor combination
  • 9 other women (19%) had the cancer stop growing for at least 6 months

So overall, 34% of the women treated with the Herceptin-Afinitor combination got some benefit from the treatment.

Herceptin is given intravenously. Afinitor is a pill taken by mouth once every day. Half the women took the Herceptin-Afinitor for 18 weeks or longer. The other half took the combination for shorter periods of time.

Both Herceptin and Afinitor can sometimes cause serious side effects, including heart and lung problems caused by Herceptin and lung problems caused by Afinitor. These types of serious side effects didn't happen in this small study. Four women developed a serious increase in blood triglyceride levels (triglycerides are fats in the blood) and one woman developed a blood clot.

While this research seems promising, more research is needed so doctors understand the best way to use the Herceptin-Afinitor combination to treat breast cancer. Other experimental mTOR inhibitors also are being studied as treatments for breast and other cancers.

If you're being treated for advanced-stage breast cancer, you and your doctor may be considering a number of treatment options, especially if the cancer has stopped responding to standard treatments. If you're willing to participate in a clinical trial, you may have even more options available, possibly including an experimental treatment such as an mTOR inhibitor. Talk to your doctor about clinical trials that might be a good fit for you and your unique situation. Visit the Breastcancer.org Clinical Trials pages for more information.

And stay tuned to Breastcancer.org to learn about the latest research on new, better ways to treat breast cancer.

Please help Breastcancer.org bring you the latest news on new targeted therapies by making a tax-deductible donation today.

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