No blood supply, no tumor.
Judah Folkman's team at the childrens hospital in Boston discovered the antiangiogenic drugs endostatin and angiostatin. They were able to show that these drugs could shrink tumors in mice.
Endostatin was tried in 140 patients and angiostatin in 65, they caused a small shrinkage in tumors but there was not great effect.
Avastin, is an antibody that blocks a key angiogenesis instigator vascular endothelial growth factor (VEGF), was tried in breast cancer, but was not good. It has been shown to be slightly beneficial in colon cancer. 403 patients with advanced colon cancer were given chemotherapy with or without avastin and the avastin improved the survival of the patients from a median of 15.6 months to 20.3 months.
The reason it does not appear to work as well in advanced breast cancer as it
does in colon cancer is that early breast cancer produces alot of VEGF but
advancd breast cancer produces alot of other angiogenic signals such as
fibroblast growth factors (), placental growth factor
(PGF) and transforming growth factor 
(TGF-).