March 2010




Taking a fractionated stereotactic approach

by Maxine Lipner Senior EyeWorld Contributing Editor


New tumor fighting technique helps to preserve vision

For patients with optic nerve sheath meningiomas, fractionated stereotactic therapy may be an attractive option, helping to preserve sight while combating the tumor, according to Robert B. Den, M.D., resident, radiation oncology, Thomas Jefferson University Hospital, Philadelphia. Recent results presented at the 2009 American Society for Therapeutic Radiology and Oncology meeting in Chicago showed that the majority of patients enjoyed stabilization of their vision following the treatments, with some even seeing improvement.

Traditionally the treatment of choice for optic nerve sheath meningiomas has been surgery. While usually effective against the tumor, there can be a significant drawback. “A very high percentage of patients go blind,” Dr. Den said. “Surgery is a good therapeutic modality because it’s very effective, but the side effect of blindness is unfortunately a reality that is unavoidable in a lot of cases.” The tug of war here is that in ensuring that the tumor is entirely removed it may be surgically necessary to destroy vision as well. “In order to clean margins, surgeons need to remove a good portion if not the entire nerve,” Dr. Den said.

Striving to preserve sight

Investigators looked to the fractionated stereotactic approach in an attempt to find a better way of dealing with this. “The main impetus was to try to find an alterative to surgery that would maintain the same level of local control but enable retention of vision,” Dr. Den said. “We wanted to find an approach that would minimize the side effects, using a fractionated approach that takes advantage of the radio biologic principle that normal tissue will have time to repair while the tumor will not.” With the stereotactic approach healthy tissue tends to rebound while the tumor does not. “You can get repair of the normal tissue around the area, but the tumor will not be able to repair itself,” Dr. Den said. “Therefore we get good tumor control and minimize side effects in the area.”

With this approach investigators targeted the radiation to the tight confines of the tumor. “We delivered stereotactic radiation with very small margins right into the area of the tumor,” Dr. Den said. “We targeted the radiation just to that area.”

Included in the study were 58 optic nerve sheath meningioma patients seen at Thomas Jefferson University Hospital between 1996 and 2006. Patients were treated to a total dose from 50- 54 gray and received 26-30 treatments. Dr. Den found the outcomes to be encouraging. “We found that our local control was greater than 95% based on MRI,” he said. “For patients who initially still had vision, 52% had stabilization of their vision and 40% actually had improvement of their vision at our last follow-up.” Only four patients had worsening of vision.

With the approach there was enough time between treatments for normal tissue to heal. “We were giving time for the vasculature to normalize and we were giving a dose that is not going to damage the nerves there,” Dr. Den said. “When you get regression of the tumor you get less pressure on the nerves and that can cause improvement or stabilization of the vision.”

Dr. Den was gratified by how well patients fared. “How well our patients were able to maintain their vision was the most interesting finding on our part,” he said. He sees the tumor type as well suited to the fractionated stereotactic approach. “These types of tumors are the locally aggressive type that doesn’t spread,” Dr. Den said. “So we have the benefit of being able to treat a very small area.”

A new standard

He views the message here as clear-cut. “I think that the clinical take-home message is that with fractionated stereotactic radio therapy we have a treatment modality that is comparable to surgery but which provides the benefit of vision preservation,” he said. “For patients who are diagnosed with this type of disease, radiotherapy should be the standard of care.”

Going forward he hopes that practitioners will move in that direction. “I would say that the exception would be those patients who have lost vision in their eye and who have very large tumors—for them, surgery would be a better approach,” Dr. Den said. “But for patients who remain with any semblance of visual acuity, this is a very attractive treatment that should be considered strongly by the ophthalmology community.”

Editors’ note: Dr. Den has no financial interests related to his comments.

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