Fluorescent Tracer 'Lights Up' Brain Tumor for Surgery
TUESDAY, Feb. 19 -- Neurosurgeons report that they harnessed the power of fluorescent light to illuminate a brain tumor so the entire growth could be removed.
A report describes a case in which a patient with glioblastoma swallowed a pill, called 5-ALA, and was taken to surgery about four hours later. The medication attached itself to tumor cells, causing them to glow brightly. Once the skull was opened, the doctors focused a blue light on the tumor, which gave the cancerous cells a pink glow, so the surgeons could differentiate malignant tissue from healthy tissue.
"This is a very, very good thing," said study author Mitchel Berger, chairman of neurosurgery at the University of California, San Francisco. "In this case, we just happened to notice we could see evidence of the tumor spreading along the way of the ventricles [a communicating network of brain cavities], which showed we could see tumor dissemination."
The authors noted that the best way to extend survival is to remove as much of the brain tumor as possible. The research is published in the Feb. 19 issue of the Journal of Neurosurgery.
It's not always easy to see precisely where a tumor has spread in the brain. Some types of tumors can be particularly difficult to identify and remove, even with the benefit of MRI and surgical microscopes.
The use of fluorescence appears to be more effective than MRI technology, at least in this case, because the glow allows surgeons to see microscopic remnants of the tumor and areas of the cancer that might be mistaken for edema, or swelling, Berger explained. "This is an inexpensive way to identify high-grade tumors," he said.
Glioblastomas are a fast-growing type of tumor that usually occurs in adults and affects the brain more often than the spinal cord, according to the U.S. National Cancer Institute.
Why do tumor cells respond differently to the fluorescent drug than the body's other cells do? Their metabolism involves porphyrin, which has a tremendous ability to absorb light, Berger explained. Porphyrin is an organic compound, like the pigment in red blood cells. The pill used in the case report is derived from porphyrin.
The report focused on the case of a 56-year-old man who had undergone resection of a glioblastoma located in the right occipital lobe of his brain in 2005. Several years later, when symptoms reappeared, an MRI scan showed three distinct, new sites of tumor in the patient's right temporal lobe.
In surgery, when the surgeons viewed the fluorescent tumor cells, they could tell rather than being a new tumor, the cancer had spread from its original location on the right side of the brain through a pathway along the wall of the right ventricle. The researchers found that the use of 5-ALA during surgery enabled them to see the actual pathway of the tumor as it had spread.
The use of 5-ALA changed the patient's prognosis. "Multi-centric disease worsens the prognosis," Berger explained.
While the technique has been used in Europe for several years, the U.S. Food and Drug Administration has not approved the use of 5-ALA in the United States. Any surgeons using 5-ALA do so with limited permission from the FDA, Berger noted. The medication, 5-ALA, is manufactured by DUSA Pharmaceuticals.
Dr. Michael Schulder, vice chairman of the department of neurosurgery at North Shore University Hospital in Manhasset, N.Y., explained that "while the FDA considers 5-ALA a drug, which would require a lengthy process for approval, neurosurgeons see it as a surgical aid, which would take far less time to get the OK."
While Schulder said he thinks 5-ALA probably will add about six months to the anticipated survival of patients with high-grade gliomas, he said that attempts to improve the ability to remove these tumors will only go so far. "In the end, however helpful the use of 5-ALA or similar compounds may be in the surgical removal of brain cancers, it won't be the answer. The treatments will have to be biological to truly have an impact on survival, and ultimately, on a cure."
Schulder said he thinks it would be possible for fluorescence to be used in other types of surgeries, if surgeons could become comfortable using a surgical microscope with the benefit of a special light (something neurosurgeons are accustomed to using). He noted that he also thinks the technique might apply to some spinal surgeries, where visualizing the spinal cord is critical.
Schulder said he thinks the use of fluorescence in cancer surgery is promising. "It's a very important concept: if you can see a tumor better, you can remove it without affecting healthy tissue."
To learn more about glioblastomas, visit the U.S. National Library of Medicine.
Posted: February 2013