HER2-positive breast cancer: What is it?

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  • With Mayo Clinic internist

    Sandhya Pruthi, M.D.

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Question

HER2-positive breast cancer: What is it?

A friend of mine has HER2-positive breast cancer. Can you tell me what this means?

Answer

from Sandhya Pruthi, M.D.

HER2-positive breast cancer is a breast cancer that tests positive for a protein called human epidermal growth factor receptor 2 (HER2), which promotes the growth of cancer cells. In about 1 of every 5 breast cancers, the cancer cells make an excess of HER2 due to a gene mutation. This gene mutation and the elevated levels of HER2 that it causes can occur in many types of cancer — not only breast cancer.

HER2-positive breast cancers tend to be more aggressive than other types of breast cancer. They're also less responsive to hormone treatment. However, treatments that specifically target HER2 are very effective. They include:

  • Trastuzumab (Herceptin). Trastuzumab, which specifically targets HER2, kills these cancer cells and decreases the risk of recurrence. Trastuzumab is often used with chemotherapy. But it may also be used alone or in combination with hormone-blocking medications, such as an aromatase inhibitor or tamoxifen. Trastuzumab is usually well tolerated, but it does have some potential side effects, such as congestive heart failure and allergic reaction.
  • Lapatinib (Tykerb). Like trastuzumab, lapatinib is a HER2-specific drug. Lapatinib may be effective for HER2-positive breast cancer that doesn't respond to trastuzumab. Lapatinib is used in combination with the chemotherapy drug capecitabine (Xeloda) and the aromatase inhibitor letrozole (Femara). Lapatinib is also being studied in combination with trastuzumab.

In addition, standard chemotherapy agents such as doxorubicin (Adriamycin) can be effective in treating HER2-positive breast cancers, although these drugs don't specifically target the HER2 protein.

Routine testing for HER2 is recommended for most women diagnosed with breast cancer because the results may affect treatment recommendations and decisions. Whenever breast cancer recurs or spreads, the cancer cells should be retested for HER2 as well as for hormone receptor status, as these can change from the original cancer in up to 20 to 30 percent of cases.

References
  1. Yamouchi H, et al. HER2 and predicting response to therapy in breast cancer. http://www.uptodate.com/home/index.html. Accessed Jan. 26, 2010.
  2. Hayes DF, et al. Systemic therapy for HER2-positive metastatic breast cancer. http://www.uptodate.com/home/index.html. Accessed Jan. 26, 2010.
  3. Pritchard KI, et al. HER2 and responsiveness of breast cancer to adjuvant chemotherapy. The New England Journal of Medicine. 2006;354:2103.
  4. Herceptin (prescribing information). South San Francisco, Calif.: Genentech, Inc.; 2009. http://www.gene.com/gene/products/information/pdf/herceptin-prescribing.pdf. Accessed Jan. 26, 2010.
  5. Tykerb (prescribing information). Research Triangle Park, N.C.: GlaxoSmithKline; 2008. http://us.gsk.com/products/assets/us_tykerb.pdf. Accessed Jan. 26, 2010.
  6. Tumor markers. American Cancer Society. http://www.cancer.org/docroot/PED/content/PED_2_3X_Tumor_Markers.asp. Accessed Jan. 28, 2010.
  7. Moynihan TJ (expert opinion). Mayo Clinic, Rochester, Minn. Jan. 27, 2010.
  8. Wolff AC, et al. American Society of Clinical Oncology/College of American Pathologists guideline recommendations for human epidermal growth factor 2 testing in breast cancer. Journal of Clinical Oncology. 2007;25:118.
  9. Fehm T, et al. Changes of serum HER2 status during clinical course of metastatic breast cancer patients. Anticancer Research. 2004;24:4205.
  10. Femara (prescribing information). East Hanover, N.J.: Novartis Pharmaceuticals Corporation; 2009. http://www.pharma.us.novartis.com/product/pi/pdf/Femara.pdf. Accessed Feb. 2, 2010.
  11. FDA expands use of approved breast cancer drug. Food and Drug Administration. http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm199374.htm. Accessed Feb. 2, 2010.
AN00495 Feb. 20, 2010

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