|
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.
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.
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 NSABP 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 ancer. 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
|
