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How Colon Cancer Treatment Redefined Preventable Blindness Worldwide

In 2013, a group of prominent historians were surveyed and asked to compile a list of the greatest breakthroughs of all time.  While some items on the list were clearly revolutionary – such as electricity (#2) and the Internet (#9), others seemed humdrum by comparison (paper at #6!), but clearly chosen for the ripple effects they would have on history and society.  

If we similarly compiled a list of the greatest breakthroughs in retinal medicine, we would need go no further than the topic of colon cancer to unveil one of the true gems. Perhaps the single most dramatic therapeutic change in retinal medicine had its origins in colorectal cancer treatment.

In 2004, the FDA approved bevacizumab (Avastin) for the treatment of metastatic colon cancer.  Bevacizumab is a humanized monoclonal antibody that inhibits vascular endothelial growth factor (VEGF) by shrinking blood vessels. Bevacizumab proved a potent chemotherapeutic adjunct, inducing tumor regression by inhibiting growth of the very blood vessels tumors critically rely on for their own growth.

New blood vessel growth is a significant source of pathology in retinal disease, most notably in wet age-related macular degeneration (AMD). With advancing age, the retinal basement membrane degenerates, and a lack of oxygen and nutrients signals development of new blood vessels. Rather than recruiting oxygen and improving the nutrient stores, these new blood vessels, or choroidal neovascular membranes, break through the retinal surface and leak blood and fluid into the retinal layers, often resulting in a severe disruption of central vision.  This quickly compounds when we realize how quickly wet AMD can lead to legal blindness, and how prevalent AMD is – affecting over 20 million Americans!

Just over a decade ago, the only reasonable treatment for these blood vessels was laser treatment that often just slowed blood vessel growth, with ineffectual lasting effect. There was no known way to reverse vision loss – all treatment focused on preventing or slowing the inevitable vision loss.  

Anti-VEGF heralded an entire new era, with impressive results. Randomized controlled trials have revealed that nearly half of patients are able to significantly reverse vision loss, improving vision by at least three lines on the eye chart. Additionally, approximately 95 percent can successfully prevent further significant loss of vision – a huge improvement!  

It soon became apparent that this treatment would work in several other cancers by inhibiting VEGF, thus gaining multiple other FDA approvals. Similarly, in retinal medicine, bevacizumab and its cohort of other anti-VEGF teammates have expanded their scope to a range of retinal pathologies, prominently diabetic retinopathy and retinal vascular occlusions – that similarly produce new blood vessels intent on stealing vision.

Whereas wet AMD was a nearly irreversible source of vision loss a decade ago, it now has superb treatments that can keep patients with wet AMD driving, reading, and continuing their day-to-day activities for years!

It’s easy to take our present outcomes for granted, and even easier to forget the critical need for continued innovation. Research and development have always been the foundation of progress in medicine, the cornerstone upon which we expand our patient outcomes. The jump from using anti-VEGF in colorectal cancer to using it in the eye was one of those breakthrough moments.

The very next innovation may be developing as we speak.  Currently, multiple clinical trials are ongoing at our research center, investigating treatments across a breadth of retinal pathology, notably the dry and wet forms of age-related macular degeneration and diabetic retinopathy – the leading causes of blindness in adults in the United States today.  These innovative treatments no longer require a trek out of town, and we look forward to your collaboration in expanding and communicating the availability of these research opportunities to your patients and colleagues.  

Author
Kapil G. Kapoor, M.D.

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