Treatment of squamous cell carcinoma of the head and neck in the metastatic and refractory settings: Advances in chemotherapy and the emergence of small molecule epidermal growth factor receptor kinase inhibitors

Approximately 475,000 cases of squamous cell carcinoma (SCCHN) of the head and neck occur worldwide. Whereas significant advances have been made in the treatment of early and locally advanced disease, the prognosis for recurrent and metastatic (R/M) disease remains poor. Compounds with demonstrated activity include cisplatin and carboplatin, antimicrotubular compounds such as taxanes and vinorelbine, and fluoropyrimidines. In refractory and metastatic disease, regimens combining platinum agents with taxanes or fluorouracil based agents produce a 30% response rate and a median overall survival of six to eight months. Newer three agent chemotherapy regimens have produced response rates in the range of 40-50%, without significant improvements in overall survival noted. Recently, a new class of medications targeting signal transduction pathways has come into focus in the treatment of various malignancies. In SCCHN, given the high prevalence of expression of the epidermal growth factor receptor (EGFR) and its role in promoting cellular growth and proliferation, molecules targeting the receptor's intracellular kinase domain are a logical strategy. The agents gefitinib and erlotinib have yielded response rates in the 5-15% range when used as single agents. In addition, newer agents with broad activity against the EGFR and other related erbB receptor family members are being developed in clinical trials. Strategies to enhance the activity of EGFR tyrosine kinase inhibitors (TKIs) in treating SCCHN are being investigated, as well as strategies to select individuals with tumors more likely to respond to these drugs. This article reviews the advances that have made in treating refractory and metastatic disease, with particular focus on the challenges that are faced in successfully translating EGFR inhibition as a paradigm of tumor treatment in SCCHN.