Cancer metastasis, the spread of cancer cells to distant organs, is responsible for 90 percent of cancer-related deaths. Cancer cells need to enter and exit circulation in order to form metastases, and the vasculature and endothelial cells are key regulators of this process. While vascularized 3D in vitrosystems have been developed, few have been used to study cancer, and many lack key features of vessels that are necessary to study metastasis. This review will focus on current methods of vascularizing biomaterials for the study of cancer, and three main factors that regulate intravasation and extravasation: endothelial cell heterogeneity, hemodynamics, and the extracellular matrix of the perivascular niche.