The epidermal growth factor receptor (EGFR) is a large protein that plays an important role in tumor growth. When EGFR is stimulated or "overexpressed," a series of chemical reactions happen that result in a tumor being "told" to grow. Researchers know that EGFR is overexpressed in many types of endometrial cancer. Cetuximab is designed to block this receptor, which may help to stop or slow the growth of tumors in those patients whose endometrial cancer has come back.