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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.
Additional Resources and References
- The study, "Cooperative Inhibitory Effect Of ZD1839 (Iressa) In Combination With
Trastuzumab (Herceptin) On Human Breast Cancer Cell Growth," is published in the
January 2002 issue of the Annals of Oncology, http://www.annonc.oupjournals.org/
- The January 24, 2002 HealthScoutNews report by Colette Bouchez is entitled
"Double Whammy for Breast Cancer."
- To learn more about Herceptin, please visit http://www.imaginis.com/breasthealth/herceptin.asp
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