Targeted therapies and radiation for the treatment of head and neck cancer: are we making progress?

Targeting specific biological pathways in tumor development has been heralded as a promising approach to the treatment of cancer. Familiar to most investigators are the studies done with epidermal growth factor receptor (EGFR) antagonists, but newer agents currently under development also target angiogenic or cell cycle pathways. EGFR activation stimulates many important signaling pathways associated with cancer development and progression, and importantly, resistance to radiation. Because EGFR overexpression portends for a worse outcome in patients with advanced head and neck cancer (HNC), selective targeting of this signaling pathway has gained attention. The agents selected for initial studies include monoclonal antibodies and tyrosine kinase inhibitors against EGFR. Encouraging laboratory findings in different xenografts resulted in rapid translation into the clinic. Results from initial clinical trials show rather surprisingly that only a minority of patients benefited from EGFR inhibition as monotherapy or in combination with chemotherapy. Current challenges for investigators are to determine (1). who will benefit from targeted agents and which agents are most appropriate to combine with radiation and/or chemotherapy, (2). how to sequence these agents with radiation and/or cytotoxic compounds, (3). reliable markers for patient selection and verification of effective blockade of signaling in vivo, and (4). mechanisms behind intrinsic or acquired resistance to targeted agents to facilitate rational development of multiple targeted therapy. Well-integrated laboratory-clinical research programs are needed to address these issues.