This Phase III trial is designed to evaluate the impact on disease progression and survival time, as well as safety, in patients following treatment with DCVax(R)-L, an immunotherapy treatment for GBM. The experimental therapy uses a patient's own tumor lysate and white blood cells from which precursors of the dendritic cells are isolated. The dendritic cell is the starter engine of the immune system. The white cells are then made into dendritic cells and they are educated to "teach" the immune system how to recognize brain cancer cells. Eligible patients will receive a series of injections of DCVax-L, to activate and then boost the immune response to the tumor cells.