All women with advanced breast cancer face a difficult and uncertain future. Most of them endure long courses of treatment that leave them looking to alternative or experimental therapies for a cure. A drug called trastuzumab (Herceptin) attacks a particularly aggressive form of breast cancer in a novel way.

One aggressive form of breast cancer is characterized by an overabundance of a protein known as human epithelial growth factor receptor-2 (HER2). This protein stimulates the growth of breast tumors. Trastuzumab is a monoclonal antibody, which blocks the HER2 receptor. This inhibits the growth of cancer cells.

Scientists have known since the 1980's that women whose breast cancers produce too much HER2 have cancers that are more aggressive and more likely to metastasize, or spread. Trastuzumab can enhance the effectiveness of standard chemotherapy treatments by targeting the HER2 receptor and inhibiting its activity.

Several clinical studies show that women with HER2-positive tumors using trastuzumab with chemotherapy have slower cancer growth and better response to treatment. An early study from 2001 showed that trastuzumab when added to chemotherapy was effective in slowing disease progression in HER2-positive breast cancer patients. In women with HER2-positive operable breast cancer, trastuzumab combined with chemotherapy improved survival outcome compared to those without trastuzumab.

Combined results of two studiesinvolving over 3,300 women found longer survival rates after one year of treatment with trastuzumab added to chemotherapy compared to those without trastuzumab.

In another study (the HERA trial), one year of treatment resulted in significant survival and less disease progression. In follow-up studies at two and four years, disease-free survival was maintained. Women who began treatment with trastuzumab after the first year of the study had similar results. There was little difference however, in overall survival or risk of death at the four-year follow-up.

Unfortunately, although trastuzumab may be able to slow the growth of cancer cells, it is also associated with some serious side effects.