Additional Study Information: The purpose of this study is to test the effectiveness (how well the drug works), safety, and tolerability of an investigational drug called nivolumab (also known as BMS-936558). Nivolumab is an antibody (a type of human protein) that is being tested to see if it will allow the bodys immune system to work against tumor cells. The effectiveness of BMS-936558 (nivolumab) in glioblastoma (GBM or brain cancer) will bedetermined by comparing the survival of subjects who receive the investigational drug BMS- 936558 (nivolumab) combined with radiotherapy to those who receive temozolomide with radiotherapy, an accepted therapy for newly diagnosed glioblastoma.