The purpose of this study is to determine the safety of this new treatment offered in this study. PCNSL can be cured in less than half of patients with standard treatment, a combination of chemotherapy and brain radiation. Also, the combination of chemotherapy and brain radiation may result in serious lasting side effects. Most patients older than age 60 develop memory problems, difficulty walking or inability to control their bladder. Some patients younger than age 60 also develop these side effects.