Laser interstitial thermal therapy (LITT) is a minimally invasive, low cost and effective approach to neurosurgery. It is especially appealing when the surgeon can control its application for precision and accuracy. Surgical resection and stereotactic radiosurgery (SRS) are the primary therapeutic interventions for the treatment of brain tumors, but they have drawbacks and limitations–and thus adjuvant therapies are considered critical for addressing brain cancer. Today’s primary adjuvant therapies, radiotherapy and chemotherapy, can be devastating to patients, however, and options such as immunotherapy and gene therapy are just emerging. So an effective yet minimally invasive and low-cost option is particularly compelling for both clinicians and patients.

All live human cells can be killed almost immediately at severely elevated temperatures (above 57°C) through various processes, including protein denaturation, coagulation, and vaporization. At lower temperatures (43°–57°C) tissular necrosis (tissue death due to protein denaturation) will occur with exposure from minutes to hours. Solid tumors in the breast, prostate, lung, liver, skin, and other organs respond to thermal therapy–the application of heat to destroy diseased tissue–in part because it can be applied minimally or noninvasively. Depending on the application and the technology, the heat source may be extracorporeal (outside the body), extrastitial (outside the tumor), or interstitial (inside the tumor).

Application of thermal therapy for treatment of brain tumors has rarely been an option. That’s partly because of limited ability to deliver sufficient energy exclusively to and selectively destroy the tumor without damaging surrounding healthy brain tissue. It’s also because of the limited ability to monitor temperature noninvasively with sufficient spatial and temperature accuracy and precision.

Laser Interstitial Thermal Therapy (LITT) AutoLITT System

A surgeon-controlled side-firing diode laser probe of AutoLITT System

Laser interstitial thermal therapy (LITT) uses a low power (3–15 W) laser with a specialized probe to heat and coagulate a tumor from within. An advantage of LITT compared to externally applied energy (e.g., high-intensity focused ultrasound) is that the energy is applied directly to the tumor rather than passing through surrounding normal tissue. Also, energy deposition is more likely to extend throughout the entire tumor.

The AutoLITT System, a LITT implementation by Monteris Medical (Winnipeg, MB, Canada), is a platform comprising MRI-compatible laser components that enable guided delivery of precision thermal therapy. Early clinical implementations of LITT for treatment of intracerebral tumors have used a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser and required irradiation times of up to 30 minutes for treatment of a single tumor.

As a critical point of differentiation, AutoLITT technology uses a thin, side-firing probe (see Fig.). The design includes the laser optical fiber designed to emit at an angle to the probe axis, a gas-cooled sapphire tip, and a rigid structure for insertion via frameless stereotactic device. This design enables the thermal damage to be confined to a specific target tissue region. Rotation and translation of the probe allow the surgeon to direct the thermal treatment selectively, sculpting each section of the tumor, and to vary the treatment parameters according to the nature of the tissue in that target zone. In addition to playing a role in directional heating, the gas-cooled probe tip allows application of higher laser powers to create larger lesions (3–4 cm), speed lesion production, and increase safety.

Source: Interconnection World, Monteris Medical Inc.