Experimental Treatment for HER2-Positive Cancers Shows Promise

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Several small, early research studies suggest that an experimental targeted therapy medicine, neratinib, may be able to treat HER2-positive, advanced-stage breast cancers some day.

HER2-positive cancers make too much of the HER2 protein. The HER2 protein sits on the surface of cancer cells and receives signals that encourage breast cancer cells to grow and spread. About one out of every four breast cancers is HER2-positive.

Herceptin (chemical name: trastuzumab) and Tykerb (chemical name: lapatinib) are targeted therapies used to treat HER2-positive breast cancer. Herceptin is used to treat both early-stage and advanced-stage, HER2-positive breast cancer. Tykerb is approved to be used in combination with the chemotherapy medicine Xeloda (chemical name: capecitabine) to treat HER2-positive, metastatic breast cancer that has stopped responding to certain chemotherapy medicines and Herceptin. Tykerb also is approved to be used in combination with the hormonal therapy Femara (chemical name: letrozole) to treat postmenopausal women diagnosed with hormone-receptor-positive, HER2-positive, advanced-stage breast cancer.

The HER2 protein receives several signals to make cells grow. These signals are called ErbB1, EeB2, and ErB4. Herceptin blocks only the ErB1 signal. Tykerb blocks the ErB1 and ErB2 signals. The experimental medicine neratinib blocks ErB1, ErB2, and ErB4. Because neratinib blocks all three signals, it is called a pan-HER2 inhibitor ("pan" means "all"). So neratinib might be a good treatment for HER2-positive breast cancers that don't respond or have stopped responding to Herceptin and/or Tykerb.

In one study, 69% of the women diagnosed with metastatic, HER2-positive breast cancer got some benefit from a combination of neratinib and the chemotherapy medicine Taxol (chemical name: paclitaxel). About 5% of these women had a complete response, which means the cancer disappeared. The other 64% of the women had a partial response, which means the cancer stopped growing or shrunk.

Another study found that 25% to 43% of women diagnosed with metastatic, HER2-positive breast cancer got some benefit from a combination of neratinib and the chemotherapy medicine Navelbine (chemical name: vinorelbine). Women who were previously treated with hormonal therapy, Tykerb, or a taxane chemotherapy (Taxol, Taxotere, or Abraxane) were more likely to respond to neratinib and Navelbine compared to women who hadn't had those earlier treatments.

Some of these early studies were phase I and phase II trials that were focusing on dose amounts and safety rather than treatment benefits. Two studies showed that diarrhea -- sometimes severe but mostly manageable -- was a common side effect of neratinib. Heart problems, including severe heart failure sometimes, are possible side effects of treatments that target the HER2 protein, including Herceptin and Tykerb. These early neratinib studies suggest that the heart problems caused by neratinib weren't bad and no severe heart failure was caused by neratinib treatment.

Neratinib is a pill taken by mouth. The combination of neratinib and the chemotherapy medicine capecitabine may be a good breast cancer treatment because both medicines are taken as pills.

Based on the results of these early studies, doctors are planning a larger study (phase III trial) to see how a combination of neratinib and Taxol work on metastatic, HER2-positive breast cancer.

If you're being treated for advanced-stage, HER2-positive 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, including an experimental treatment such as neratinib. 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.

Editor’s Note: On July 17, 2017, the U.S. Food and Drug Administration approved Nerlynx (chemical name: neratinib) to treat early-stage, HER2-positive breast cancer for an extended period after surgery in people who have previously been treated with Herceptin (chemical name: trastuzumab).

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