Sight for sore eyes
Plaque brachytherapy saves vision in some patients with ocular melanoma
MUSC Health ophthalmologist George N. Magrath, M.D., and radiation oncologist S. Lewis Cooper, M.D., are collaborating to make a potentially vision-saving radiotherapy available to South Carolina patients with choroidal melanoma.
A diagnosis of choroidal melanoma once left surgeons with no choice but to remove the eye, since in 40 percent of cases the cancer spreads to the liver and lungs and is uniformly lethal. However, the Collaborative Ocular Melanoma Study showed that survival was no better in patients whose eye was removed than in those who underwent a form of radiotherapy known as plaque brachytherapy, which in some patients can not only spare the eye, but also save some vision.
In plaque brachytherapy, a gold disk or “plaque” studded with radioactive seeds is custom fit to the tumor and seated in the back of the eye for a specified number of days, during which the patient is hospitalized. It is effective in killing the tumor in 98 percent of cases.
Although the procedure was pioneered more than three decades ago, it only became available in South Carolina last year. Patients with choroidal melanoma were once left with a harsh choice — lose an eye or travel outside the state to a center offering plaque brachytherapy. Many patients were referred to the Wills Eye Hospital in Philadelphia, a recognized center of excellence in this procedure.
When Magrath, an MUSC graduate, returned to take a faculty post last year after completing a fellowship at Wills Eye Hospital, he was determined to make this procedure available to patients closer to home, at MUSC’s Storm Eye Institute.
The collaboration with Cooper and the radiation oncology team enabled him to bring to the Lowcountry new advances in the field that improve the chances of preserving vision.
Using 3D reconstructions of the eye, Cooper and the other radiation oncologists customize the radiation dose to the tumor and plan the deployment to minimize risk to the structures of the eye crucial for vision.
“What Lewis (Cooper) does and what they are really good at in radiation oncology is that they will tinker with the radiation and pull it away from the optic nerve and the critical structures of the eye,” says Magrath. “They can customize it down to fractions of a millimeter.”
The struggle to save vision continues in the two years after surgery, when radiation and the dying tumor take their toll on the macula and optic nerve. The damage done by radiation is similar to that seen in patients with diabetes, and some common diabetes medications, such as vascular epithelial growth factor (VEGF) inhibitors, are proving useful in combating radiation damage.
Radiation blocks blood flow to the retina, increases inflammation and leads to loss of different retinal cells. This causes the retina to signal for new blood vessels to grow by releasing VEGF. These new blood vessels are leaky and bleed into the eye, causing swelling and eventual scarring of the macula and the optic nerve. VEGF inhibitors help prevent the formation of these blood vessels. New postoperative laser treatments target the ischemic retina to prevent it from releasing the harmful growth factors. Corticosteroids are used to reduce the inflammation caused by the dying tumor.
“We are now able to save most of the eyes,” says Magrath. “If we can catch the tumors when they are small, we can do a really good job of saving the eye and potentially some vision.”