The goal of this single arm Phase I feasibility study is to investigate the tolerability of cannabis with concurrent chemoradiation in the treatment of glioblastoma multiforme (GBM). A strain of cannabis provided by The National Institute of Drug Abuse (NIDA) that has a high concentration of cannabidiol (CBD) and a low concentration of THC (relative to average street cannabis) will be tested in order to maximize clinical efficacy while minimizing intoxicating side effects in this medically-ill population.