U.S. Government Clinical Trials Find Herceptin an Effective 'Targeted' Treatment for Breast Cancer (dateline May 9, 2005)
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 positive 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.