1. Subjects with primary central nervous system (CNS) tumor or CNS tumor involvement. However, subjects with metastatic CNS tumors may participate in this study if the subject is: >4 weeks from prior therapy completion (including radiation and/or surgery); Clinically stable with respect to the CNS tumor at the time of study entry; Not receiving steroid therapy in treating CNS tumor or CNS tumor involvement; Not receiving anti-convulsive medications (that were started for brain metastases).