Laser Interstitial Thermal Therapy (LITT) in Neurosurgery Supplement
Laser interstitial thermal therapy (LITT) was introduced in the 1980s as a new technique in minimally invasive surgery. Essentially, the use of laser light allows the deposition of a precise amount of energy to a defined area at the tip of a fiber. The energy transmitted by the laser fiber is absorbed by tissues surrounding the tip and converted into heat. At temperatures between 55°C and 95°C, photocoagulation occurs, leading to rapid, irreversible tissue damage. Early on, the technique gained traction in the treatment of hepatic tumors and varicose veins, but the inability to monitor tissue damage and to protect eloquent structures initially hampered its use in neurosurgery. With the introduction of magnetic resonance thermography, which harnesses the temperature dependence of the proton resonance frequency to generate an accurate real-time map of tissue temperature, the treatment of deep-seated lesions in critical areas became feasible.
In the early 2000s, small studies by Schwarzmaier, Leonardi, and others started to show encouraging results for the treatment of recurrent glioblastomas, with survival exceeding what is typically seen with the current standard of care. In 2007, the first commercially available LITT system gained US Food and Drug Administration approval, and the popularity of the technique has grown steadily.
LITT has a number of unique features that make it of particular use in neuro-oncology and led to rather rapid adaptation in the field. Because only a small stab incision is used and closure consists of a single stitch, the risk of wound complications is negligible, and adjuvant therapy can be initiated almost immediately after surgery. This is of great theoretical benefit in the treatment of rapidly growing tumors such as glioblastomas. Furthermore, it avoids the significant risk of wound complications with reoperations on irradiated scalp. Most patients can be discharged home with minimal pain the day after surgery, and some institutions have shifted away from monitoring all patients in the intensive care unit postoperatively. In addition, there is mounting evidence that LITT interrupts the blood-brain barrier, and studies investigating whether it can be used to enhance chemotherapy delivery are underway.
LITT is uniquely suited for the treatment of deep-seated metastases that have failed stereotactic radiosurgery because there is essentially no other safe and effective treatment available. This is becoming increasingly relevant as our methods of treating systemic cancer are expanding, in many cases allowing long-term survival when intracranial disease can also be controlled. LITT is also useful for focally recurrent glioblastoma, with several studies showing robust improvement in survival. Increasingly, the technique is being used for glioblastomas of the thalamus, insula, or corpus callosum, which have generally been considered inoperable by most. Current treatment options for these tumors are limited and outcomes are poor, but early studies are showing that, with LITT, survival in select cases approaches the results seen with maximal safe open resection of noneloquent glioblastomas.
Separately, LITT has found a role in the treatment of temporal lobe epilepsy because it allows the creation of a precise lesion along the amygdala and hippocampus. Although seizure control rates appear to be somewhat inferior to open temporal lobectomy and selective amygdalohippocampectomy, the procedure is generally well tolerated, and because of its minimally invasive nature, it has the potential to reach a large segment of epilepsy patients who would be good surgical candidates but have shied away from open surgery. Recently, LITT has also been investigated as an alternative to separation surgery for spinal epidural metastases, with early results showing a reduction in tumor size and encouraging improvement in pain and functional status.
As with any emerging technology, many questions remain unanswered. Continued work is needed to refine the indications for LITT in cranial and spinal oncology and epilepsy surgery. Furthermore, the technology is far from mature; efficiency and ease of use will need to be improved to aid in broad adaptation of the technique. Many hurdles remain to be overcome, but it appears that LITT is here to stay as an additional tool in the neurosurgeon’s armamentarium, and we are looking forward to following its evolution in the years to come.
Dr Komotar is a paid consultant of Medtronic. Dr Buttrick has no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.