Magnetic resonance guided laser induced thermal therapy for brain metastases recurrence

Radiation necrosis and brain metastases recurrence are common sequelae after radiation therapy for brain metastasis. The differentiation of radiation necrosis and recurrent brain metastases continues to remain a difficult task despite a number of diagnostic methods. Techniques including magnetic resonance imaging, diffusion-weighted imaging, nuclear studies, and the gold standard of biopsy have all been studied for their effectiveness in accurately diagnosing the postradiation condition. Various specific treatment options of the distinct pathologies are available with the general theory that recurrences require more immediate treatment whereas radiation necrosis can be observed until symptomatic before intervention. This further emphasizes the necessity to accurately diagnose the condition to start appropriate and effective treatment. Despite both pathologies being pathophysiologically distinct, controversies exist as to whether there should be a distinction made at all or if the two can be perceived as a single condition if treatment and presentation are similar enough. Furthermore, a single treatment option such as Magnetic resonance guided laser induced thermal therapy can be used, potentially eliminating the need to differentiate the 2 entities because it successfully treats both conditions while being minimally invasive ¹⁾.

Several recent studies have successfully described the use of Magnetic resonance guided laser induced thermal therapy for managing brain metastases and support the feasibility as a surgical treatment option for radiographically regrowing lesions failing radiosurgery ^{2) 3) 4) 5) 6) 7)}.

This option is increasing in experience in the USA ⁸⁾.

Clinical data for 30 patients across 4 centers were retrospectively reviewed. Patients were included if they received Laser Thermal Ablation (LTA) therapy following radiosurgical failure due to radiation necrosis or tumor regrowth. Demographics, surgical data, and follow-up imaging and clinical information were collected. Linear regression analyses were performed to determine treatment factors that were associated with post-LTA outcome.

The large majority of patients responded favorably to LTA treatment with low complication rates (23%), short length of stay (53% ≤ 2 d) and reductions in perilesional edema (63%). A total of 73.3% of patients stopped steroids and 48% saw improvement of their preoperative symptoms. Patients with better pre-LTA Karnofsky Performance Status had better survival. Patients who had lesions with more perilesional T2 change post-LTA had a better chance of weaning off steroids and obtaining symptomatic relief.

MRI-guided laser thermal ablation therapy serves as a viable alternative to traditional treatment options for metastatic brain lesions failing radiosurgery. Although this study is limited by size and is retrospective, LTA therapy may result in symptomatic improvement and a more prominent reduction in fluid-attenuated inversion-recovery signal for larger lesions ⁹⁾.

All patients with recurrent posterior fossa metastatic lesions treated with MR-LITT by the senior neurosurgeon were included in the study. Preoperative and postoperative follow-up magnetic resonance imaging (MRI) studies were used to measure lesional and perilesional edema volume. These measurements were compared to calculate percent ablation volume. All patients' clinical examinations were followed closely.

Four patients with recurrent cerebellar metastases were treated with MR-LITT. The average percent lesion ablated was 97.1% (range, 88.2%-100%). The average preoperative lesion volume was 3.3 cm3 (range, 1.1-7.2 cm3), and the average final postoperative volume was 3.8 cm3 (range, 0.5-7.6 cm3). Lesion volume increased to maximum volume on postoperative day 1, with an average increase of 486.9%. The extrapolated average time for the lesion to shrink to below the initial size was 294.5 days. There was a trend toward a decrease in average edema volume from the preoperative MRI of 17.8 cm3 to final postoperative follow-up MRI of 3.4 cm3 (P = 0.0952). No postoperative hydrocephalus or complications occurred.

This pilot study shows that LITT appears to be a safe and promising treatment for recurrent posterior fossa metastatic lesions up to 7.2 cm3. Further randomized controlled studies are warranted to further characterize the long-term efficacy of this therapy ¹⁰⁾.

Six patients who had previously undergone gamma knife stereotactic radiosurgery for brain metastases were selected. All patients had an initial favorable response to radiosurgery but subsequently developed regrowth of at least one lesion associated with recurrent edema and progressive neurological symptoms requiring ongoing steroids for symptom control. All lesions were evaluated for craniotomy, but were deemed unresectable due to deep location or patient's comorbidities. Stereotactic biopsies were performed prior to the thermotherapy procedure in all cases. LITT was performed using the Visualase system and follow-up MRI imaging was used to determine treatment response. In all six patients biopsy results were negative for tumor and consistent with adverse radiation effects also known as radiation necrosis. Patients tolerated the procedure well and were discharged from the hospital within 48 h of the procedure. In 4/6 cases there was durable improvement of neurological symptoms until death. In all cases steroids were weaned off within 2 months. One patient died from systemic causes related to his cancer a month after the procedure. One patient had regrowth of the lesion 3 months after the procedure and required re-initiation of steroids and standard craniotomy for surgical resection. There were no complications directly related to the thermocoagulation procedure. Stereotactic laser induced thermotherapy is a feasible alternative for the treatment of symptomatic regrowing metastatic lesions after radiosurgery. The procedure carries minimal morbidity and, in this small series, shows some effectiveness in the symptomatic relief of edema and neurological symptoms paralleled by radiographic lesional control. Further studies are necessary to elucidate the safety of this technology ¹¹⁾.

Iyer et al. report a challenging case of a brain metastasis located in the motor cortex, which was not responsive to radiosurgery. Use of a novel technique, magnetic resonance-guided laser-induced thermotherapy (MRgLITT), resulted in the complete obliteration of the lesion without adverse effects or evidence of tumor recurrence at follow-up. This case illustrates that MRgLITT may provide a viable alternative for patients with brain metastases refractory to radiosurgery or in deep locations, where both stereotactic radiosurgery (SRS) and surgical resection may be ineffective ¹²⁾.