This information is provided to us by our Board Member and medical advisor, Dr. Arthur Fu of West Coast Retina.
What is Avastin?
Avastin is also known as Bevacizumab and is made by Genentech. This drug is a special medicine that blocks a receptor found on blood vessels, known as vascular endothelial growth factor (VEGF), that causes blood vessels to leak, and new blood vessels to grow (also known as neovascularization). Blocking VEGF causes blood vessels to stop leaking, and new blood vessels to stop growing until the medicine wears off. Avastin was FDA approved for patients with certain cancers/tumors because this effect could shrink the cancer without typical chemotherapy side effects. Retina doctors began using small portions of the medicine to inject directly into the eyes with patients who have retinal problems from blood vessel leakage and neovascularization, such as diabetic retinopathy and macular degeneration. Despite being approved by the FDA for cancers, Avastin is NOT approved by the FDA specifically for the eye. Patients sign a consent form allowing the retina specialist to use the drug knowing the FDA has not approved Avastin (also known as off label use).
How is Avastin used to treat Coats’ Disease?
Coats’ Disease is characterized by uncontrolled blood vessel leakage, and occasionally neovascularization. Although we don’t know the exact cause of Coats’ Disease, a common problem with the disease is blood vessel leakage. Avastin can stop the leakage and neovascularization in many patients, although the Coats’ Disease is not cured and visual loss cannot always be restored.
Why do doctors prescribe it so frequently?
Retina specialists use Avastin because if Coats’ is caught early enough, Avastin can be used. Avastin is generally thought to be very safe, and can be given quickly and without major surgery. Compared to other drugs, when given in the eye, it is also not very expensive. Other drugs that are approved by the FDA, cost thousands of dollars. Avastin, when used in individual syringes made by special pharmacies may cost less than 100 dollars
Does it work? What’s the rate of success?
Avastin works. However, it all depends upon how severe the leakage is, how early the Coats’ Disease is found/diagnosed. Remember, Coats’ Disease does not currently have a cure. If a patient has permanent retinal damage, the Avastin my make the existing leakage go away, but not restore permanently damaged retina. Therefore, patients may not have noticeable improvement in vision. Also, Coats’ Disease, because of its rarity is hard to study. We don’t know percentages of who gets better, and if VEGF is produced equally in all patients with Coats’ disease.
What are the risks?
Avastin, when given as an injection to adults is typically safe. The biggest fears were potential stroke, but there is no clear evidence that patients are at higher risk. The procedure in which Avastin is given requires a procedure known as intravitreal injection, which can rarely 0.03-0.05% of the time, can cause a severe infection within the eye, known as endophthalmitis. Finally, the long term effects of Avastin on children is unknown. Though there are no reports of direct effects, because it has not been studied formally by the FDA on children, there are potential unknowns as children grow.
What are some common misconceptions about Avastin injections?
The most common misconception about Avastin is that it is chemotherapy. Chemotherapy usually causes direct poisoning of rapidly dividing cells such as cancer cells, but also normal hair cells and gastrointestinal cells. Avastin is not that kind of drug, so patients do not get hair loss or lose weight. The other big misconception that patients may have is that Avastin “cures” Coats’ Disease. The benefits can be temporary, and the Avastin may need to be repeated or laser given.