Monoclonal antibodies have been used in a variety of ways in the management of cancer including diagnosis, monitoring, and treatment of disease. The U.S. Food and Drug Administration (FDA) has approved numerous monoclonals for the treatment of cancer (Table 13.1). Among the unmodified monoclonal antibodies, Panitumumab (Vectibix), cetuximab (Erbitux) and bevacizumab (Avastin) are now marketed for metastatic colorectal cancer, trastuzumab (Herceptin) for breast cancers that overexpress HER-2 receptors, and alemtuzumab (Campath) for B cell lymphocytic leukemia (B-CLL). Several other monoclonal antibodies are in late-stage clinical trials. With the general availability of these agents, it appears that antibody-based therapeutics have an established role in clinical oncology.

Radio-immunotherapy (RIT) utilizes an antibody labeled with a radionuclide to deliver cytotoxic radiation to a target cell. In cancer therapy, a monoclonal antibody (mAb) with specificity for a tumor-associated antigen is used to deliver a lethal dose of radiation to the tumor cells. The ability of the antibody to specifically bind to a tumor-associated antigen increases the dose delivered to the tumor cells while decreasing the dose to normal tissues. While antibodies armed with drug conjugates and immunotoxins kill only the targeted cell, radionuclide conjugates can exert a bystander effect, destroying adjacent cells that lack antigen expression. With external beam therapy, only a limited area of the body is irradiated. However, RIT, like cytotoxic chemotherapy, is a systemic treatment that, in principle, can eliminate metastatic disease throughout the body.