Some patients with nasopharyngeal carcinoma show evidence of infection with the virus that causes infectious mononucleosis Epstein Barr virus (EBV) before or at the time of their diagnosis. EBV is found in the cancer cells of almost all patients with advanced stage NPC, suggesting that it may play a role in causing the disease. The cancer cells infected by EBV are able to hide from the body's immune system and escape destruction. We want to see if special white blood cells, called T cells, that have been trained to recognize and kill special parts of EBV infected cells can survive in blood and affect the tumor.