Laser interstitial thermal therapy (LITT) of the brain – Experiences and new indications

The glioma is the most common type of primary brain tumor; more than 40% of gliomas are malignant. For decades, open microsurgical resection and postoperative radiochemotherapy have been the international standard methods of treatment.

During the last few years, the importance of the (sub-) total tumor resection has been recognized, especially in respect of the patient’s progression-free survival time. Different modalities of neuronavigation [1, 2], intraoperative imaging (“open MR” system) and intraoperative fluoroscopy with 5-ALA [3] have proved to be important technical achievements to support this aim.

However, the overall survival time of patients with anaplastic gliomas is poor. Successful curative treatments are statistically insignificant. As a result, it was and still is important to find new adjuvant methods to treat (recurrent) brain tumors. One of the most promising minimally invasive procedures is the laser interstitial thermal therapy (LITT), performed under stereotactic or “open” magnetic resonance imaging (MRI) guidance.

Stephen G. Bown [4] was the first person to introduce LITT into tumor therapy in the early 1980s and since the middle of the 1990s, LITT has become an accepted method in the (adjuvant) minimally-invasive treatment of brain tumors. Our research group at the University Hospital of Düsseldorf started with the therapy of benign gliomas (WHO grade II) in eloquent regions [5, 6] and optimized the method (image-guided and image-/thermo-controlled) in the 0.5 Tesla “open MRI scanner” Signa SP [7, 8]. We started treating recurrent glioblastomas in 1997. In 2002 and 2006, we presented the method and our experiences with the treatment of benign and anaplastic gliomas [9, 10]. Our recent work at the University of Cologne has been concerned with the use of PET scans in the planning and control of LITT in malignant, recurrent gliomas [11].

Further pioneering research in the use of LITT for brain tumors was done in the USA, especially by the groups of Peter Black [12] (Neurosurgery) and Ferenc Jolesz [13] (Neuroradiology, Development of the “open MRI”) at the Harvard Medical School.

Many other centers and research groups have been founded throughout the USA. Due to different, mainly non-medical reasons, there are only a few European centers who treat small groups of patients [14, 15], mainly for gliomas. LITT for brain and other metastases, as well as innovative indications, are meanwhile more frequent in the USA.

Under special conditions, it has even been used as a first line therapy, as we did ourselves in single, unpublished cases in patients with small gliomas (<3 cm in diameter), benign and malignant, who refused open surgery and radiation. They showed a promising course of disease, equal to the effect of recent standard therapy.

During the last 20 years, LITT has proved to be an adjuvant, minimally-invasive method in the treatment of brain tumors/lesions of the central nervous system as well as for other indications, for example in general surgery, lung surgery, liver metastases and breast cancer treatment. Voigt and Torchia [16] give a current review of literature in this issue.

Several important advantages of LITT, compared to other adjuvant methods, are obvious:

• No known side effects

• No limitation with respect to the patients’ age and Karnofsky performance status (local anesthesia is possible)

• Repeatable as often as indicated (without limitation of applied kJ), as soon as tumor recurrence occurs

• Ideal for lesions in eloquent regions that are otherwise unsuitable for surgery

• Indicated in benign and malignant tumors (and other lesions)

• Blood-brain barrier is modulated/opened during, and for a defined period after LITT, so that the effect of chemotherapy might be improved [9, 17]

• Easily adaptable to size and shape of the lesion (several target applications in one session possible) [9, 10, 12]

• “One time – one place” procedure, especially when performed under image-guided navigation in “open MRI”

International meetings, such as the 9th International Interventional MRI Symposium at the Harvard Medical School (Boston, September 22–23, 2012) [18], showed the current wide interest in this minimal-invasive method. Neurosurgeons and neurologists, as well as general surgeons and other surgical fields, were involved, and presented their recent experiences [18]. (Neuro-) radiologists are continuously improving MRI before, during and after LITT procedures, to improve both the efficiency and safety of the different treatments.

The purpose of this special issue is to give an overview of current developments, technical improvements and new indications for the use of LITT in the central nervous system – for example as a causal therapy in the treatment of epileptic seizures, even in children, or post-radiation lesions in gliomas as presented in this issue by various research groups [19–21].

A great deal of research still has to be carried out in the future, especially in the field of the optimized laser energy dose/radiation time in special tumor entities and localizations, as well as in the choice of different types of laser for special indications.