 The purpose of this study is to find out whether the addition of a drug called Avastin avastin to the two-drug combination of carboplatin and paclitaxel shrinks tumors better than the two-drug combination alone in the treatment of endometrial cancer. Avastin is a humanized monoclonal antibody a type of protein that is normally made by the immune system to help defend the body from infection and cancer produced by Genentech, Inc. Avastin is an antibody directed against vascular endothelial growth factor, or VEGF. VEGF is a potent, specific growth factor with a well defined role in normal and abnormal blood vessel formation. It is present in a wide variety of normal tissues, but is produced in excess by most solid cancers tumors. In the setting of cancer, VEGF promotes the growth of blood vessels that feed the tumor cells. 