What do they have in common? Vascular Endothelial Growth Factor (VEGF) happens to be the common denominator between cancer, diabetic retinopathy and “wet” macular degeneration. Surprising that the latest treatments for the the eye are the same chemotherapy treatments for a variety of cancers? Does it seem to you that Avastin is used to treat diabetic macular edema, diabetic retinopathy and wet macular degeneration?
Unrestricted Blood Vessels – In macular degeneration, the “wet” form of the disease is defined by the presence of choroidal neovascularization. These are abnormal blood vessels growing between the layers of the retina.
Cancerous tumors enjoy unrestricted growth. As the tumors continue their growth, the tissue requires blood supply. The tumor growth is dependent upon…neovascularization, the growth of new blood vessels. There are two stages of diabetic retinopathy, non-proliferative and proliferative. “Proliferative” is defined as the unrestricted growth of…blood vessels.
VEGF – Vascular endothelial growth factor was discovered by cancer researchers in the 1980’s. A similar protein was long suspected to be integral in the chain of events causing proliferative diabetic retinopathy. When I was training in the late 1980’s and early 1990’s, we always spoke of a potential protein/agent causing the abnormal proliferation of blood vessels in the eye.
As it turns out, tumors secrete VEGF to allow both the formation and maintenance of the vascular tree. So too, does the eye in cases of diabetic retinopathy and wet macular degeneration. The VEGF induces the formation of new blood vessels and keeps them “alive.” When VEGF is blocked, by anti VEGF medications such as Avastin, the growth of the blood vessels stops and the existing vessels shrivel.
Vascular Endothelial Growth Factor was originally known as vascular permeability factor (VPF). For our purposes, VPF causes blood vessels to become incompetent, or leaky. This is the case in diabetic macular edema. The normal retinal blood vessels leak, causing fluid to accumulate in the retina/macula, leading to decreased vision. Presumably, by blocking VPF (=VEGF) the vessels stop leaking. This would explain why, or how, anti-VEGF medications seem to be effective in treating macular edema.
What Does This Mean? Obviously, I am not a cancer researcher, but Avastin is FDA approved for multiple cancers (certain types of brain, lung, kidney, colon, etc.). It seems that by focusing treatment on the common denominator of all tumore, i.e. blood vessels, a variety of treatments have emerged. While such targeted chemotherapy is not new in medicine, it is new to ophthalmology.
I wrote today to underscore that it seems that anti-VEGF/Avastin seems to be indicated for every aspect of macular degeneration and diabetic retinopathy. It is not your imagination, nor your misunderstanding of your reading…it’s true.
Randall V. Wong, M.D.
Ophthalmologist, Retina Specialist