Researchers Investigate Combination Herceptin/Iressa Treatment for Breast Cancer Patients (dateline February 28, 2002)
The results of a preliminary study find that combining the drugs Herceptin and Iressa may be effective in treating some breast cancer cases. Both drugs work by targeting certain growth factors on the surface of breast cancer cells, which are present in moderate or high amounts in some patients. Though the study was conducted on cells in a laboratory, the researchers believe the new combination "targeted" therapy holds promise in preventing the spread of breast cancer in patients whose cancers contain certain growth factors.
HER2 is a growth factor 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 growth factor is altered, extra HER2 receptors may be produced. This over-expression of HER2 causes increased cell growth and reproduction, often resulting in more aggressive breast cancer cells. HER2 over-expression affects approximately 25% to 30% of breast cancer patients. Women with HER2 over-expression may not be as responsive to standard breast cancer treatments, including certain regimens of chemotherapy.
The drug Herceptin (generic name, trastuzumab) works by attaching itself to HER2 receptors in breast cancer cells. By binding to HER2 receptors, Herceptin blocks the growth and spread of these cancer cells. Iressa is a very new, experimental drug which is thought to block another type of growth factor called EGFR (EGFR is found in moderate amounts in approximately 70% of breast cancer cases). Researchers are investigating whether Iressa (ZD 1839) may also be effective at treating lung, colorectal, stomach, ovarian, and prostate cancers.
To conduct their study on Herceptin and Iressa, Italian researchers used breast cancer cells that contained EFGR and excess amounts of HER2. The cells were treated every 24 hours with either a combination of Herceptin and Iressa, Herceptin alone, or Iressa alone.
According to lead researcher Dr. Nicola Normanno, the goals of the study were: to determine whether Iressa could prevent the growth of cancer cells that contained excessive amounts of the HER2 growth factor and moderate amounts of the EGFR growth factor; and, to see whether combination therapy with Iressa and Herceptin was effective against breast cancer. When the researchers analyzed the cells after five days, they found that the combination therapy was significantly more effective at controlling the growth of cancer cells than either drug alone. The combination therapy controlled cancer growth by 70%, versus 55% with Iressa alone and 30% with Herceptin alone.
Though the study was performed on cells in a laboratory, the researchers believe the results may eventually have important implications for breast cancer patients. According to Dr. Normanno, Iressa/Herceptin therapy is likely to help prevent the spread of breast cancer if it is administered early, before the disease has progressed significantly. However, because of the experimental nature of the combination drug therapy, it is likely to only be used on women with advanced breast cancer (that has spread to other body organs) until it can be proven to be effective.
Herceptin is currently approved by the U.S. Food and Drug Administration (FDA) to treat advanced breast cancer patients whose breast cancers over-express the HER2 growth factor. Studies are underway to determine whether Herceptin is also effective in early-stage breast cancer patients with high amounts of HER2. Iressa has not yet received FDA approval; its effectiveness is still being evaluated in clinical trials.