This phase II/III trial tests how well adding mycophenolate mofetil, to the usual treatment with intensity-modulated radiation therapy and temozolomide works for the treatment of glioblastoma that may have spread from where it first started to nearby tissue, lymph nodes, or distant parts of the body (advanced). Mycophenolate mofetil blocks enzyme activity which can disrupt tumor activity and may make the tumor more sensitive to radiation and/or temozolomide. Intensity modulated radiation therapy is a type of 3-dimensional radiation therapy that uses computer-generated images to show the size and shape of the tumor. Thin beams of radiation of different intensities are aimed at the tumor from many angles. This type of radiation therapy reduces the damage to healthy tissue near the tumor. Temozolomide is a chemotherapy drug and in a class of medications called alkylating agents. It damages the cell's deoxyribonucleic acid (DNA) and may kill cancer cells. Giving mycophenolate mofetil with intensity-modulated radiation therapy and temozolomide may be more effective than intensity-modulated radiation therapy and temozolomide alone for the treatment of advanced glioblastoma.