Real-time magnetic resonance-guided laser thermal therapy for focal metastatic brain tumors

We report the initial results of a pilot clinical trial exploring the safety and feasibility of the first real-time magnetic resonance-guided laser-induced thermal therapy of treatment-resistant focal metastatic intracranial tumors.

Patients with resistant metastatic intracranial tumors who had previously undergone chemotherapy, whole-brain radiation therapy, and radiosurgery and who were recused from surgery were eligible for this trial. Under local anesthesia, a Leksell stereotactic head frame was used to insert a water-cooled interstitial fiberoptic laser applicator inside the cranium. In the bore of a magnetic resonance imaging (MRI) scanner, laser energy was delivered to heat the tumor while continuous MRI was performed. A computer workstation extracted temperature-sensitive information to display images of laser heating and computed estimates of the thermal damage zone. Posttreatment MRI scans were used to confirm the zone of thermal necrosis, and follow-up was performed at 7, 15, 30, and 90 days after treatment.

In all cases, the procedure was well tolerated without secondary effect, and patients were discharged to home within 14 hours after the procedure. Follow-up imaging showed an acute increase in apparent lesion volume followed by a gradual and steady decrease. No tumor recurrence within thermal ablation zones was noted.

In this ongoing trial, a total of four patients have had six metastatic tumors treated with laser thermal ablations. Magnetic resonance-guided laser-induced thermal therapy appears to provide a new, efficient treatment for recurrent focal metastatic brain disease. This therapy is a prelude to the future development of closed-head interventional MRI techniques in neurosurgery.