All cancerous tumors rely on angiogenesis, the growth of new capillary blood vessels, for a supply of oxygen and nutrients. Since brain tissue is by nature rich with blood vessels, brain tumors are viewed as highly dependent upon angiogenesis.¹ Tumors stimulate blood vessel growth by releasing proteins, called growth factors, into the surrounding tissues.

The primary angiogenesis-promoting growth factor is vascular endothelial growth factor (VEGF). VEGF both stimulates the formation of new capillaries and makes tumor blood vessels abnormally permeable and leaky. This feature causes fluid to seep out of the capillaries into surrounding brain tissue, causing brain swelling.² To treat the build-up of fluid and swelling, physicians typically administer high doses of steroids to patients, which cause a variety of undesirable side effects.