A three dimensional (3D) model of a glioblastoma tumor made of a synthetic material and a plurality of cell types, including malignant cells and non-malignant cells of the tumor. Methods of forming the 3D tumor model are also provided, as well as systems in which the 3D tumor model can be perfused and fluidly connected to a medium containing immune cells and/or other cells and factors present in the tumor's microenvironment. Methods utilizing the 3D tumor model or the system in, for example, personalized therapy, are also provided.