There are proteins found on the surface of cells called receptors that receive signals and send signals to the cell to grow or to die. Dacomitinib is an oral drug that blocks a receptor called the epidermal growth factor receptor (EGFR) which is found to be too active in SCCHN patients. By blocking the signals for the cancer cells to grow, it is believed to stop or slow the growth of tumor cells. The treatment of SCCHN usually includes chemotherapy and radiation.