The blood brain barrier (BBB) is a major obstacle to drug delivery in the treatment of malignant brain tumors including Glioblastoma multiforme (GBM). MRI-guided laser ablation (MLA) has been noted to disrupt peritumoral BBB, which could then lead to increased access of new tumor antigens to the lymphovascular system and vice versa of immune effector cells to the tumor for effective activation of the immune system. Therefore the combination of MK-3475 and MLA as proposed in this protocol is hypothesized to create a therapeutic synergy in which MLA increases material access to promote immune activation and then MK-3475 maximizes these tumor-specific immune reactions to impart effective tumor control.