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Chapter 081. Principles of Cancer Treatment (Part 25)

Antibodies In general, antibodies are not very effective at killing cancer cells. Because the tumor seems to influence the host toward making antibodies rather than generating cellular immunity, it is inferred that antibodies are easier for the tumor to fend off. Many patients can be shown to have serum antibodies directed at their tumors, but these do not appear to influence disease progression. However, the ability to grow very large quantities of high-affinity antibody directed at a tumor by the hybridoma technique has led to the application of antibodies to the treatment of cancer. Clinical antitumor efficacy has been obtained. | Chapter 081. Principles of Cancer Treatment Part 25 Antibodies In general antibodies are not very effective at killing cancer cells. Because the tumor seems to influence the host toward making antibodies rather than generating cellular immunity it is inferred that antibodies are easier for the tumor to fend off. Many patients can be shown to have serum antibodies directed at their tumors but these do not appear to influence disease progression. However the ability to grow very large quantities of high-affinity antibody directed at a tumor by the hybridoma technique has led to the application of antibodies to the treatment of cancer. Clinical antitumor efficacy has been obtained using antibodies where the antigen-combining regions are grafted onto human immunoglobulin gene products chimerized or humanized or derive de novo from mice bearing human immunoglobulin gene loci. Such humanized antibodies against the CD20 molecule expressed on B cell lymphomas rituximab and against the HER-2 neu receptor overexpressed on epithelial cancers especially breast cancer trastuzumab have become reliable tools in the oncologist s armamentarium. Each used alone can cause tumor regression rituximab more than trastuzumab and both appear to potentiate the effects of combination chemotherapy given just after antibody administration. Antibodies to CD52 are active in chronic lymphoid leukemia and T cell malignancies. EGF-R-directed antibodies such as cetuximab and panitumomab have activity in colorectal cancer refractory to chemotherapy particularly when utilized to augment the activity of an additional chemotherapy program and in the primary treatment of head and neck cancers treated with radiation therapy. The mechanism of action is unclear. Direct effects on the tumor may mediate an antiproliferative effect as well as stimulate the participation of host mechanisms involving immune cell or complement-mediated response to tumor cell-bound antibody. Alternatively the antibody may alter .