In this article a brief story of mathematical model for one of the most lethal tumor, GBM, is considered, and it tries to reduce the amount of dose delivery to the patient by using genetic algorithm (GA). Since this tumor kills many of its patients, lots of efforts have been done in the previous decades in order to cure this cancer or at least increase its patients' lifetime. Most of previous models have not been associated with a treatment term but in this investigation the latest model of the tumor which contains the input term of radiotherapy has been utilized. This paper shows a new optimization solution on the latest model of GBM and reduces the total dose received by the patient while he or she has the same lifetime.