(June 18, 2012 - Insidermedicine)
Recent research in the Canadian Journal of Ophthalmology shows that those treated with Avastin have a 12 times higher risk of developing severe inflammation in the eye when compared to patients who received Lucentis. This complication can lead to significant visual loss. Watch now to learn more about eye injections and this increased risk.
To view our animated whiteboard video that explains the heated health policy debate surrounding these two drugs, click here
The eye is very similar to a camera. Both are optical systems, which bend light rays and focus them onto a film. In the eye, the thin film located in the back of the eye is called the retina.
One of the leading causes of vision loss and blindness is macular degeneration. In this condition the small cells in the back of the eye degenerate and no longer function properly. Most people with macular degeneration have small yellow aging spots just under retina called drusen. In addition, there may be loss or growth of pigmented cells. If these are sign are seen, we classify the disease as the dry type of macular degeneration.
One out of 10 patients with macular degeneration can develop a very aggressive form of this disease, in which blindness can quickly occur. This is called the wet type of macular degeration and happens because a small blood vessels starts to grow under the retina. In this situation, a small molecule, called VEGF, is released in the back of the eye and causes new blood vessels to grow. These blood vessels are very fragile and can allow fluid to leak out and cause the retina to be boggy or they can raise the risk of bleeding in or under the retina.
The treatment of wet macular degeneration had been revolutionized by the development of molecules that are designed to stick to VEGF and bind to it. These molecules, called anti-VEGF compounds, ultimately lower the levels of VEGF in the eye. With time, blood vessels shrink and vision stabilizes or returns. Lucentis, is one such compound and consists of a fragment of an anti-VEGF antibody. It has been approved through most regulatory agencies across the world and was developed specifically as an ocular grade medication to be used in the eye. Based on research published in the New England Journal of Medicine, this medication can prevent further vision loss in 95% of patients and can improve vision in nearly 4 out of ten patients. This medication is delivered into the eye by a procedure called an intravitreal injection. In this delicate procedure, a tiny needle enters the eye through the small space created by the back of the lens and the front of the retina. Once the needle tip is in the vitreous, or jelly of the eye, one twentieth of a cc is injected into the eye. This medication is dosed monthly and numerous injections are needed ot manage this condition. This medication is expensive and its retail price is around $1700 in Canada.
Another medication, called Avastin, is also commonly used by retina specialists to treat wet macular degeneration. Avastin is a molecule that is significantly larger than Lucentis and consists of an entire antibody to VEGF. This biologic agent was developed for colorectal cancer but retina specialists started to be use it while Lucentis was still under development and was not yet available for use.
Avastin has not undergone the same level of scientific testing that Lucentis has, in part because it is not approved for use in the eye by health regulatory bodies like Health Canada and the FDA. One significant advantage of using Avastin, however, is that it costs significantly less than Lucentis – commonly retailing for between $100-$300. The low price is based on the fact that the volume of medication needed to be injected in the eye is very small as compared to the amount of medication used to treat colorectal cancer. To get the medication, some specialized pharmacies will obtain a dose of Avastin and split it into many small doses and send them to retina specialists.
While Avastin is used with equal frequency to Lucentis in many practices our research published this month in the Canadian Journal of Ophthalmology shows that there may be a higher risk of severe inflammation in the eye following injection with Avastin, when compared to Lucentis. To perform our study, we reviewed a consecutive series of patients who underwent treatment with treatment with either of the 2 medications. We reviewed nearly 1600 consecutive injections over a 3-year period and found that those who received Avastin were 12 times more likely to develop a serious inflammation within the eye. Many patients had severe pain 1-2 days following the injection and presented to us with pus located in the front of the eye or the vitreous. On average, patients who had this complication lost 6 lines of vision on an eye chart. This complication was seen following injection with Lucentis in one case, but ultimately they ended up gaining vision.
Cases of severe intraocular inflammation have been noted in many other centers and both Health Canada and The Canadian Ophthalmology Society are now actively tracking adverse events seen with these medications. The increased risk that we observed may be explained by the fact that Avastin is a complete antibody whereas, Lucentis is only a portion of it. Importantly Lucentis doesn’t contain an Fc component that binds to T cells. This raises the chance that the eye’s immune system may see Avastin as being foreign and initiate an immune reaction against it. The increase risk may also be due to elements of splitting and storing Avastin. It is possible that foreign contaminants are introduced into the syringe at the time of splitting the medication into smaller doses or storing it in the syringes prior to injection.
Overall intravitreal injection is a very safe procedure and an adverse event doesn’t occur often. However, if you are a patient who is receiving an intravitreal injection you should be aware that side effects can include inflammation, infection and stroke. If you have worsening pain and eye redness following an intravitreal injection, you should seek urgent medical attention.
For Insidermedicine, I am Dr. Sanjay Sharma.