In 2021 the TSSS Research Committee launched a Ground-breaking Research Essay Contest where TSSS members were encouraged to write on a surgical topic that fascinated them.

We are very pleased to announce the winner of the 2021 TSSS Ground-breaking Research Essay Contest:

MRI-guided Laser Interstitial Thermal Therapy (LITT) is a ground-breaking minimally invasive surgical technique with superior precision. It is being implemented in the treatment of inoperable brain tumours, epilepsy, radiation necrosis and cerebral metastases.1-2 This technique involves the selective ablation of a lesion or structure in the brain by utilising the thermal energy of a laser.2 The first reported use of a laser in neurosurgery on a human was in 1966, however, this surgery was not successful. It was only after new advances in thermal imaging, laser delivery techniques and the implementation of MRI guidance that LITT was reintroduced as a ground-breaking treatment for intracranial pathologies.2 In this essay we will be taking a closer look at the procedure itself, the indications for and efficacy of the technique, the possible complications, the cost-effectiveness and the future of LITT in neurosurgery.

FIGURE 1: THE LITT SYSTEM CONTAINING AN MRI SCANNER, LASER SYSTEM AND WORKSTATION 3

Mechanism

The LITT system consists of an MRI scanner, laser system and workstation. The laser system is responsible for generating the laser and transmitting it via optical fibres to the pathology or lesion being treated. The workstation creates a real-time thermal map that is used for monitoring during the procedure and estimating tissue necrosis, by using MRI images taken before and during the procedure.
The procedure starts with preprocedural stereotactic MRI to plan the trajectory of the laser. Inside the operating room, the patient is positioned according to pathology location and spacing inside the intraoperative MRI.2,4 An incision of 5 mm is made at the entry site and a drill is used to make a burr hole. A guide is fixed to the skull and the fibre optic laser probe is advanced according to the planned trajectory into the centre of the pathological lesion. The patient is then placed in the intraoperative MRI scanner, images are taken and the ablation process is initiated. Laser firing is coordinated according to the real-time thermal map generated by the workstation. After completion, the laser is removed and the patient is monitored for 24 hours before being discharged.2,4
Currently, there are two FDA-approved LITT systems: NeuroBlate and Visualase. The main difference between the two systems is the type of laser and cooling system being used. The laser results in the heating of the tissue of the pathological lesion causing enzyme and protein denaturation, melting of membrane lipids, vessel sclerosis and finally coagulation necrosis.1

FIGURE 2: NEUROBLATE LASER SYSTEM 3

Indications and Efficacy

LITT has been used to treat inoperable tumours, such as gliomas, and other pathologies such as epilepsy, radiation necrosis, and chronic pain.1-2 In the treatment of gliomas and other brain metastases, LITT has been proven to be a safe and effective procedure. In patients with recurrent grade 3 and 4 glioblastomas, LITT had an improved median overall survival of 20.9 months when compared with chemotherapy (11.1-16 months), craniotomy (14.8 months) and high dose brachytherapy (18.9 months).2 LITT is a promising alternative to open surgery in the treatment of epilepsy and achieved a 53% and 57% remission rate of disabling seizures, in two studies respectively.2 Radiation necrosis and chronic pain have been successfully treated, however, the procedure only achieved temporary relief in the treatment of chronic pain.2 LITT has also been used to treat Parkinson’s disease and achieved marked improvements in tremors.5 LITT has many benefits when compared to conventional craniotomies, including smaller incision size, shorter hospital stays, decreased haemorrhage and postoperative pain and can reach tumours in surgically inaccessible areas. However, it is not free of complications.1-2,6

Complications

Complications of LITT include arterial injuries, wound infection, oedema, neurological deficits and thermal injuries to other structures.1-2 However, LITT has a very low complication rate, between 5.7% and 9%, whereas conventional craniotomies have a 13.9% complication rate.1-2, 7-8 The reduced complication rate of LITT can be attributed to the small incision and the precision of the procedure which reduces the risk of wound infection and damage to nearby structures and increases cost-effectiveness.
FIGURE 2: NEUROBLATE LASER SYSTEM 3

Cost-effectiveness

LITT fares favourably against open surgery in terms of cost-effectiveness. This is due to shorter hospital stays, fewer discharges to rehabilitation facilities and a lower chance of readmission. LITT patients had an average hospital stay of 3 days, whereas craniotomy patients stayed for 7 days on average. Likewise, 14.1% of craniotomy patients were readmitted after 30 days, whereas no LITT patients were readmitted.9

The Future of LITT

LITT will continue to shape the future of neurosurgery, as its potential grows. LITT has the potential to improve drug delivery of adjuvant therapies to pathological tissue in the brain, by breaking down the blood-brain barrier in the perioperative period.6 Furthermore, LITT also has the potential to improve tumour-specific immunity by increasing tumour antigen presentation and activating antigen-presenting dendritic cells, due to its hyperthermic properties.6 By exploiting and understanding these pathways, LITT can greatly improve the treatment modalities of brain metastases.
LITT is the latest ground-breaking neurosurgical technique that is used in the treatment of recurrent gliomas and other pathologies such as metastases, epilepsy, and radiation necrosis. It is minimally invasive and fares favourably against conventional craniotomies in terms of safety, complication rates, and cost-effectiveness. The potential of LITT in neurosurgery will continue to evolve and shape the future treatment of inoperable pathological lesions and metastases.

About the Author

Estiaan Mellet is a dedicated and driven second year MBChB student. He completed his matric in 2019 and achieved 9 distinctions at Curro College Hazeldean. He was accepted to study Neuroscience at the University of California Los-Angeles, but he ultimately decided to study medicine here in Pretoria. He has a strong interest in neurological and neurosurgical related topics and hopes to specialize in paediatric neurosurgery one day.

References

1. Missios S, Bekelis K, Barnett GH. Renaissance of laser interstitial thermal ablation. Neurosurg Focus [Internet]. 2015 [cited 2021 Jul 22]; 38(3):E13. Available from: https://thejns.org/focus/view/journals/neurosurg-focus/38/3/article-pE13.xml doi:10.3171/2014.12.Focus14762

2. Salem U, Kumar VA, Madewell JE, Schomer DF, de Almeida Bastos DC, Zinn PO, et al. Neurosurgical applications of mri guided laser interstitial thermal therapy (litt). Cancer Imaging [Internet]. 2019 [cited 2021 Jul 22]; 19(1):65. Available from: https://cancerimagingjournal.biomedcentral.com/articles/10.1186/s40644-019-0250-4 doi:10.1186/s40644-019-0250-4

3. Tyc R, Torchia M, Beccaria K, Canney M, Carpentier A. Magnetic Resonance-Guided Laser Interstitial Thermal Therapy: Historical Perspectives and Overview of the Principles of LITT. 2020. p. 1-17.

4. Patel B, Kim AH. Laser interstitial thermal therapy. Mo Med [Internet]. 2020 [cited 2021 Jul 23]; 117(1):50-5. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7023945/

5. San Luciano M, Katz M, Ostrem J, Martin A, Starr P, Ziman N, et al. Effective interventional magnetic resonance image-guided laser ablations in a parkinson’s disease patient with refractory tremor. Mov Disord Clin Pract [Internet]. 2015 [cited 2021 Jul 24]; 3(3):312-4. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6353372/ doi:10.1002/mdc3.12283

6. Rodriguez A, Tatter SB. Laser ablation of recurrent malignant gliomas: Current status and future perspective. Neurosurgery [Internet]. 2016 [cited 2021 Jul 24]; 79(suppl_1):S35-S9. Available from: https://academic.oup.com/neurosurgery/article/79/suppl_1/S35/2748343 doi:10.1227/neu.0000000000001442

7. Rennert RC, Khan U, Bartek J, Jr, Tatter SB, Field M, Toyota B, et al. Laser ablation of abnormal neurological tissue using robotic neuroblate system (laantern): Procedural safety and hospitalization. Neurosurgery [Internet]. 2019 [cited 2021 Jul 25]; 86(4):538-47. Available from: https://academic.oup.com/neurosurgery/article/86/4/538/5487982 doi:10.1093/neuros/nyz141

8. Barnett GH, Voigt JD, Alhuwalia MS. A systematic review and meta-analysis of studies examining the use of brain laser interstitial thermal therapy versus craniotomy for the treatment of high-grade tumors in or near areas of eloquence: An examination of the extent of resection and major complication rates associated with each type of surgery. Stereotact Funct Neurosurg [Internet]. 2016 [cited 2021 Jul 25]; 94(3):164-73. Available from: https://www.karger.com/Article/FullText/446247 doi:10.1159/000446247

9. Dhawan S, Bartek J, Chen CC. Cost-effectiveness of stereotactic laser ablation (sla) for brain tumors. Int J Hyperthermia [Internet]. 2020 [cited 2021 Jul 30]; 37(2):61-7. Available from: https://www.tandfonline.com/doi/full/10.1080/02656736.2020.1774084 doi:10.1080/02656736.2020.1774084