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Two U.S. government clinical trials find that the drug Herceptin (generic name,
trastuzumab) can significantly reduce the recurrence of breast cancer in women with an aggressive form of
the disease, when given in combination with chemotherapy. In the studies, breast cancer patients who received
Herceptin along with standard combination chemotherapy had a 52 percent decrease in disease recurrence
compared to patients treated with chemotherapy alone. Herceptin appears to only work in women whose breast
cancers are classified as "HER-2 positive," meaning that they make too much of a protein called HER-2, found
on the surface of cancer cells. Researchers and cancer experts call the study findings significant and
potentially life-saving for the 20% to 30% of breast cancer patients with HER-2 positive cancers.
These findings confirm that we now have a very potent weapon against the recurrence of cancer cells
that overexpress HER-2," said researcher Edith A. Perez, MD, a medical oncologist at the Mayo Clinic in
Jacksonville, Florida, in a National Cancer Institute news release.
HER2 (human epidermal growth factor receptor 2) is a protein found on the surface of cells that, when
functioning normally, has been found to be a key component in regulating cell growth. However, when the
HER2 protein is altered, extra HER2 protein receptors may be produced. This over-expression of HER2
causes increased cell growth and reproduction, often resulting in more aggressive breast cancer cells.
Women with HER2 over-expression may not be as responsive to standard breast cancer treatments,
including certain regimens of chemotherapy.
Herceptin works by targeting breast cancer cells that have too many copies of the HER2 protein. After it
has identified which cells over-express the HER2 protein, Herceptin attaches itself to the HER2
protein receptors on the surface of these cells. By binding to the cells, Herceptin slows the
growth and spread of tumors that have an overabundance of HER2. Many experts believe that Herceptin
represents the future direction of breast cancer drugs in that it targets a particular protein of the
cancer cell and prevents it from carrying out its action, similar to the new leukemia drug, Gleevec.
The two Herceptin clinical trials were sponsored by the National Cancer Institute (NCI), part of the
National Institutes of Health, and conducted by a network of researchers led by the National
Surgical Adjuvant Breast and Bowel Project (NSABP) and the North Central Cancer Treatment
Group (NCCTG), in collaboration with the Cancer and Leukemia Group B, the Eastern Cooperative
Oncology Group, and the Southwest Oncology Group. Research results were announced in the spring
of 2005 and published in the October 20, 2005 issue of The New England Journal of Medicine.
The studies involved over 3,300 women with HER2 postive breast cancers. Patients were randomly selected
to receive either standard chemotherapy (with the drugs doxorubicin and cyclophosphamide) followed by treatment
with the drug paclitaxel, or the same form of standard chemotherapy followed by treatment with the drugs
paclitaxel and Herceptin. Most patients who enrolled in the studies had breast cancers that had spread to
their nearby lymph nodes.
Women who were treated with chemotherapy and Herceptin were significantly less likely to experience a recurrence of
their disease. "This is a major advance for many thousands of women with breast cancer," said U.S. National
Cancer Institute Director Andrew C. von Eschenbach, MD, in an NCI news release. "These results are one more
example that we are at a major turning point in the use of targeted therapies to eliminate suffering and
death from cancer."
Other cancer experts agreed that the studies are a significant advance in targeted breast cancer
treatment. "These are truly life-saving results in a major disease," said JoAnne Zujewski, MD of
the National Cancer Institute, in an NCI news release. Edward Romond, MD, study chair for the National Adjuvant Breast
and Bowel Project and professor of oncology at the University of Kentucky, in Lexington, Kentucky,
noted, "For women with this type of aggressive breast cancer, the addition of [Herceptin] to
chemotherapy appears to virtually reverse prognosis from unfavorable to good."
HER2 testing is becoming more common among women diagnosed with breast cancer.
Knowing the results of the test can help physicians and patients determine which treatment options
are most likely to be effective. HER2 testing is performed on cancer cells that have been removed during
breast biopsy or breast cancer surgery. Testing may also be performed on cells from
a breast tissue sample that has been stored from a previous biopsy (many laboratories
keep tissue samples for years after the initial biopsy or surgery). Testing for HER2 protein
over-expression involves staining the tissue sample with a specific solution in a pathology
laboratory. The pathologist then examines the cells within the tissue sample, checking for highlighted
areas where high levels of HER2 over-expression are present. Depending on the level of
staining, the patient's cancer may be classified as HER2 positive or HER2 negative.
Additional Resources and References
- "Trastuzumab after Adjuvant Chemotherapy in HER2-Positive Breast Cancer," was published in the October 20, 2005
issue of The New England Journal of Medicine, Volume 353:1659-1672, http://content.nejm.org/
- The April 25, 2005 NCI news release, Herceptin® Combined With Chemotherapy Improves Disease-Free Survival for Patients With
Early-Stage Breast Cancer," was published on the NCI website, http://www.cancer.gov/
- To learn more about Herceptin, please visit
http://www.imaginis.com/breasthealth/herceptin.asp
- Genentech, the manufacturer of Herceptin, provides full prescribing information on the drug at
http://www.herceptin.com/
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