EGFR-targeting monoclonal antibodies in head and neck cancer

The epidermal growth factor (EGF) and its receptor were discovered nearly 40 years ago. Over the past decade interruption of this pathway has been exploited in the treatment of various solid tumors. Antibodies that interfere with ligand binding to and dimerization of the EGFR (and small molecules that inhibit the EGFR tyrosine kinase) are anti-proliferative, radiosensitizing, and synergistic with DNA-damaging cytotoxic agents. Proposed mechanisms of radio- and chemosensitization include enhanced apoptosis, interference with DNA repair and angiogenesis, receptor depletion from the cell surface and antibody-dependent cell-mediated cytotoxicity. This article provides the reader with a comprehensive review of EGFR-targeting antibodies under development for the treatment of head and neck squamous cell cancer (HNSCC) and also summarizes relevant clinical data in this disease with small molecule EGFR inhibitors. One of the monoclonal antibodies, cetuximab, recently received full FDA approval for the treatment of patients with locoregionally advanced (with radiation) or metastatic HNSCC (as a single agent). Regulatory approval followed reporting of a large international study in which the addition of cetuximab to definitive radiation therapy in HNSCC resulted in statistically significant improvements in locoregional control and overall survival. Results of the pivotal trial, other clinical data supporting the regulatory approval, and a preview of the next generation of clinical trials are presented. Considerable work remains to be done, particularly to enhance our understanding of factors that may predict for favorable response to EGFR inhibitor therapy and to evaluate the impact of integrating anti-EGFR therapies into complex chemoradiation programs delivered with curative intent.