Women with Early Stage Breast Cancer: Wonder Drug May Help Her-2

The news that the world's first targeted therapy, trastuzumab (Herceptin), is now available for many women with early-stage HER2-positive breast cancer may be a significant advancement in the treatment of breast cancer.

Between 25 percent and 30 percent of breast cancer is HER2-positive, meaning that growth-promoting HER2 proteins are overly abundant on the outside of the cancer cells, promoting an aggressive disease. HER2 pushes a cell to divide, and while a little on a cell is normal, a lot is not. No one knows why, in these so-called "HER2-positive" tumors, these proteins are over-expressed. But when this happens, cancer becomes aggressive.

Trastuzumab is a specific type of biologic therapy, a monoclonal antibody, designed to shut down activity of these HER2 proteins by sticking to and "smothering" them, halting the pro-growth molecular instructions that these proteins relay into the body of the cancer cells. When approved by the FDA in 1998, trastuzumab helped usher in the era of targeted therapy because it specifically attacks a molecular defect on a cancer cell.

The first use of trastuzumab, however, was in women whose cancer was the most difficult to treat, because it had spread beyond the breast. Still, when used with chemotherapy, trastuzumab reduced tumor size by more than 50 percent, and extended survival, according to investigators who conducted these clinical studies. The best response to trastuzumab was seen in patients with the highest levels of HER2 protein in their tumors, proving the therapy was truly zeroing in on the right molecular target.

The clear benefit of adding trastuzumab to chemotherapy for patients with advanced breast cancer, considering its overall tolerability, led several investigators to develop studies in the late 1990s. Researchers sought to test how the drug would treat HER2-positive cancer before it had a chance to spread. They believed that if the drug could help women with the poorest prognosis, the benefit it could offer women with the earliest stages of invasive, HER2-positive breast cancer might be dramatic.