Laser ablation of brain lesions
One of the greatest challenges of treating patients with brain lesions is balancing the need to maximize cytoreduction while minimizing approach-related morbidity. For patients with metastatic brain tumor or radiation necrosis, open surgery not only poses risks of functional loss but also can require cessation of chemotherapy, thereby disrupting ongoing cancer treatment.
At Mayo Clinic in Rochester, Minnesota, minimally invasive laser surgery is available to treat certain brain lesions. The technology is similar to that used at Mayo Clinic to treat patients with focal, medication-resistant epilepsy. The MRI-guided laser ablation has been used to treat metastatic brain tumors and radiation necrosis for only about nine months, but preliminary results are promising.
"We can potentially treat these tumors, or at least control them locally, and spare the patient from undergoing craniotomy," says Jamie J. Van Gompel, M.D., a consultant in the Department of Neurologic Surgery at Mayo Clinic in Rochester, Minnesota. "We can also potentially reduce or avoid steroid therapy, which can cause weight gain and other problems for patients when used chronically."
The laser surgery is performed by Dr. Van Gompel and by Ian F. Parney, M.D., Ph.D., a consultant in the Department of Neurologic Surgery at Mayo Clinic in Rochester, Minnesota. The procedure is done through a 4-millimeter burr hole in the back of the skull. A laser catheter is positioned optimally in the tumor; in some cases, more than one catheter may be used to maximize the volume of tumor that can be ablated. The patient, under general anesthesia, is then placed in an MRI scanner. Real-time MRI guidance generates a temperature map of the patient's brain while laser ablation is underway.
The procedure takes about four hours. There is a small risk of missing the target and causing a bleed in the lesion. However, that risk is minimized by the laser's hemostatic properties.
"The advantage of this system is that we can put a laser catheter deep into these problem areas," Dr. Van Gompel says. "When we do that, we avoid the approach-related morbidities that might occur with brain retraction."
The system facilitates precise navigation of the laser and monitoring of brain tissue temperature during ablation. "Under MRI guidance, we can watch as we heat the tissue," Dr. Van Gompel says. "We can input specific reference points on the MRI, so we don't heat beyond a specific zone. We can also heat tissue to a precise threshold and monitor the temperature very accurately."
In patients who have undergone the procedure at Mayo Clinic, lesions have been well-treated without complications. Dr. Van Gompel cites the example of a patient whose colorectal cancer metastasized to a single brain lesion. After treatment with Gamma Knife radiation, the patient developed a nodular recurrence that was treated with laser ablation.
"He left the hospital the day after the procedure with no pain medications," Dr. Van Gompel says. "He felt well and was able to continue with his chemotherapy without disruption."
Mayo Clinic recently added a second laser ablation system that, rather than targeting a single sphere, can fire around the laser's tip — allowing for more conformal treatment. Dr. Van Gompel expects that Mayo Clinic neurosurgeons may soon be able to treat recurrent gliomas with laser ablation.
"This treatment modality is in the very early stages," he says. "But in select patients, there is a substantial advantage to this procedure."