Jason Collins said he's first going to Singapore to receive a targeted therapy with the goal of keeping the tumors in check while a personalized immunotherapy is made for him. We don't know which personalized immunotherapy he will get, but his glioblastoma diagnosis was determined at UCLA, so I'm certain his consultation there must have gone over his best options for beating this.
I would like to point out that his tumor is considered unresectable, but that does not mean tumor tissue cannot be harvested for a personalized immunotherapy like DCVax-L. Unresectable means that a full or near-total resection of the tumor is not recommended or possible. For DCVax-L, just a small 2 gram portion of the tumor is needed to make a full course of doses.