Tuesday, February 23, 2016

Intravitreal injections for Age related macular degeneration: what's the score?

1.75 million people in the US have exudative age related macular degeneration.  For the past 10 years these patients have been going to their eye doctor every month for an injection into the eye.  It must be a worthwhile treatment to keep people coming back for an injection into their eye.  It got me thinking about what the true evidence is behind these treatments.

The first step to creating a Treatment Score was to identify the diagnosis.  I decided to focus in on exudative age related macular degeneration.  A quick search on PubMed identified the most common and reliable outcome measure, the National Eye Institute Visual Function Questionnaire - 25.  This questionnaire is aimed to identify the true functional vision and changes in function of patients with a treatment.  The hope is that it is a bit more practical method to assess treatments to see an improvement in patients' lives.  

Once the diagnosis and outcome were identified, I picked the treatments.  There are three anti-VEGF molecules used for AMD.  Lucentis is a very common VEGF inhibtior with a good deal of evidence in the literature, therefore, I picked Lucentis as the treatment.  I also identified the alternative treatment, photodynamic therapy, as an alternative treatment.  

Now that the diagnosis, treatments, and outcomes have been identified, I am able to start searching the literature and building the Star Blocks.  I created two Star Blocks for Lucentis, one for the ANCHOR trial and another for the MARINA trial.  These trials each enrolled more than 400 patients and were well structured.  With these Star Blocks entered, I was able to get a Treatment Score for Lucentis in exudative AMD.  

Lastly, we have to account for treatment burden and the possible side effects of intravitreal injections. There is a monthly or an as needed approach to intravitreal injections and a large randomized controlled trial showed that both approaches are efficacious with a small benefit from monthly injections.  Given that patients must come at least every 6-8 weeks, and likely monthly, to get the visual improvement, we included treatment burden in the secondary statistics as a negative to the treatment.  The dreaded complication of intravitreal injections is endophthalmitis and severe ocular inflammation.  In the largest retrospective trial I could find, the rate was about 0.85/1000 injections.  While a rare complication, we included it in the secondary statistics because of the gravity of the side effect.  

You'll see from the Treatment Score Calculator that the NEI VFQ-25 increased in both studies and patients experienced a very good improvement in visual function with these treatments.  When taken into account with the secondary statistics for treatment burden and post injection severe inflammation, we are able to calculate a Treatment Score of 85.  This represents good scientific evidence that vision can be improved with intravitreal injections of anti-VEGF agents for exudative macular degeneration.  Next week we'll compare this with PDT to assess which treatment has the best evidence.  (See the disclaimers below.)

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