Lung cancer is the leading cause of cancer deaths throughout the industrialized world, and colorectal cancer is not far behind. Untreated individuals with lung cancer survive an average of eight months, with a five-year survival rate of only 15 percent for treated patients. Similarly, only 9 percent of persons with advanced colorectal cancers that have spread (metastasized) survive five years beyond diagnosis. Depending upon the specific cancer type and stage of progression, surgery, radiation therapy, or drugs are the preferred treatment approaches.
Under ideal conditions, cancer chemotherapy (chemo) only kills cancer cells, while leaving normal cells untouched. Unfortunately, ideal conditions are not the reality. Existing chemo is, at best, more toxic to cancer cells, but all cells are damaged, leading to a wide range of side effects.
Biologic drugs, which include monoclonal antibodies, are designed to specifically target receptors located on the surface of cells that when over-activated can cause cancer. One of these is the epidermal growth factor receptor (EGFR), whose over-activity has been implicated in some cases of lung cancer and colorectal cancer. Approved for use in 2003 and 2004, Iressa (gefitinib) and Erbitux (cetuximab) block EGFR and are used for the treatment of lung cancer and colorectal cancer, respectively. Because of their serious side effects and questionable effectiveness, both drugs are often backups to other types of treatment.
Iressa is marketed in some sixty-six countries worldwide. In many countries in Europe and Asia, it has been approved for use alone as the first treatment for advanced cases of non-small-cell lung carcinoma (NSCLC). However, some clinical studies show that chemo-treated patients live longer than with Iressa. Thus, in the United States, Iressa has only been approved for individuals who have not benefited from chemotherapy.
Erbitux, when used with the chemo drug Camptosar (irinotecan), slows the growth of colon and rectal tumors. However, it does not improve the quality of life or increase the survival time of patients with advanced cases. Moreover, it has not been found to benefit patients whose colon cancer has not spread. The effectiveness of Erbitux remains to be shown in the clinics.
SEE ALSO Biologic Drugs (1982), Herceptin (1998).
The top of this image shows a microscopic view of excised lung cancer that has replaced normal lung tissue.