Local therapy in glioma: An evolving paradigm from history to horizons (Review)

Despite the implementation of multimodal treatments after surgery, glioblastoma (GBM) remains an incurable disease, posing a significant challenge in neuro-oncology. In this clinical setting, local therapy (LT), a developing paradigm, has received significant interest over time due to its potential to overcome the drawbacks of conventional therapy options for GBM. The present review aimed to trace the historical development, highlight contemporary advances and provide insights into the future horizons of LT in GBM management. In compliance with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols criteria, a systematic review of the literature on the role of LT in GBM management was conducted. A total of 2,467 potentially relevant articles were found and, after removal of duplicates, 2,007 studies were screened by title and abstract (Cohen's κ coefficient=0.92). Overall, it emerged that 15, 10 and 6 clinical studies explored the clinical efficiency of intraoperative local treatment modalities, local radiotherapy and local immunotherapy, respectively. GBM recurrences occur within 2 cm of the radiation field in 80% of cases, emphasizing the significant influence of local factors on recurrence. This highlights the urgent requirement for LT strategies. In total, three primary reasons have thus led to the development of numerous LT solutions in recent decades: i) Intratumoral implants allow the blood-brain barrier to be bypassed, resulting in limited systemic toxicity; ii) LT facilitates bridging therapy between surgery and standard treatments; and iii) given the complexity of GBM, targeting multiple components of the tumor microenvironment through ligands specific to various elements could have a synergistic effect in treatments. Considering the spatial and temporal heterogeneity of GBM, the disease prognosis could be significantly improved by a combination of therapeutic strategies in the era of precision medicine.

Magnetic Resonance-Guided Laser Interstitial Thermal Therapy for Management of Low-Grade Gliomas and Radiation Necrosis: A Single-Institution Case Series

BACKGROUND

Laser interstitial thermal therapy (LITT) has emerged as a minimally invasive treatment modality for ablation of low-grade glioma (LGG) and radiation necrosis (RN).

OBJECTIVE

To evaluate the efficacy, safety, and survival outcomes of patients with radiographically presumed recurrent or newly diagnosed LGG and RN treated with LITT.

METHODS

The neuro-oncological database of a quaternary center was reviewed for all patients who underwent LITT for management of LGG between 1 January 2013 and 31 December 2020. Clinical data including demographics, lesion characteristics, and clinical and radiographic outcomes were collected. Kaplan-Meier analyses comprised overall survival (OS) and progression-free survival (PFS).

RESULTS

Nine patients (7 men, 2 women; mean [SD] age 50 [16] years) were included. Patients underwent LITT at a mean (SD) of 11.6 (8.5) years after diagnosis. Two (22%) patients had new lesions on radiographic imaging without prior treatment. In the other 7 patients, all (78%) had surgical resection, 6 (67%) had intensity-modulated radiation therapy and chemotherapy, respectively, and 4 (44%) had stereotactic radiosurgery. Two (22%) patients had lesions that were wild-type IDH1 status. Volumetric assessment of preoperative T1-weighted contrast-enhancing and T2-weighted fluid-attenuated inversion recovery (FLAIR) sequences yielded mean (SD) lesion volumes of 4.1 (6.5) cm³ and 26.7 (27.9) cm³, respectively. Three (33%) patients had evidence of radiographic progression after LITT. The pooled median (IQR) PFS for the cohort was 52 (56) months, median (IQR) OS after diagnosis was 183 (72) months, and median (IQR) OS after LITT was 52 (60) months. At the time of the study, 2 (22%) patients were deceased.

CONCLUSIONS

LITT is a safe and effective treatment option for management of LGG and RN, however, there may be increased risk of permanent complications with treatment of deep-seated subcortical lesions.

Association of intraoperative end-tidal carbon dioxide level with ablation volume during magnetic resonance-guided laser interstitial thermal therapy for mesial temporal lobe epilepsy

OBJECTIVE

Maximal safe ablation of target structures during magnetic resonance-guided laser interstitial thermal therapy (MRgLiTT) is critical to achieving good seizure outcome in patients with mesial temporal lobe epilepsy (mTLE). The authors sought to determine whether intraoperative physiological variables are associated with ablation volume during MRgLiTT.

METHODS

Patients with mTLE who underwent MRgLiTT at our institution from 2014 to 2019 were retrospectively analyzed. Ablation volume was determined with volumetric analysis of intraoperative postablation MR images. Physiological parameters (systolic blood pressure [SBP], diastolic blood pressure [DBP], mean arterial pressure [MAP], end-tidal carbon dioxide [ETCO2]) measured 40 minutes prior to ablation were analyzed. Univariate and multivariate regression analyses were performed to determine independent predictors of ablation volume.

RESULTS

Forty-four patients met the inclusion criteria. The median (interquartile range) ablation volume was 4.27 (2.92-5.89) cm3, and median ablation energy was 7216 (6402-8784) J. The median MAP, SBP, DBP, and ETCO2 values measured during the 40-minute period leading up to ablation were 72.8 (66.2-81.5) mm Hg, 104.4 (96.4-114.4) mm Hg, 62.4 (54.1-69.8) mm Hg, and 34.1 (32.0-36.2) mm Hg, respectively. In univariate analysis, only total laser energy (r = 0.464, p = 0.003) and 40-minute average ETCO2 (r = -0.388, p = 0.012) were significantly associated with ablation volume. In multivariate analysis, only ETCO2 ≤ 33 mm Hg (p = 0.001) was significantly associated with ablation volume.

CONCLUSIONS

Total ablation energy and ETCO2, but not blood pressure, may significantly affect ablation volume in mTLE patients undergoing MRgLiTT. Mild hypocapnia was associated with increased extent of ablation. Intraoperative monitoring and modulation of ETCO2 may help improve extent of ablation, prediction of ablation volume, and potentially seizure outcome.

Two-trajectory laser amygdalohippocampotomy: Anatomic modeling and initial seizure outcomes

OBJECTIVE

Laser interstitial thermal therapy (LITT) for mesial temporal lobe epilepsy (mTLE) is typically performed with one trajectory to target the medial temporal lobe (MTL). MTL structures such as piriform and entorhinal cortex are epileptogenic, but due to their relative geometry, they are difficult to target with one trajectory while simultaneously maintaining adequate ablation of the amygdala and hippocampus. We hypothesized that a two-trajectory approach could improve ablation of all relevant MTL structures. First, we created large-scale computer simulations to compare idealized one- vs two-trajectory approaches. A two-trajectory approach was then validated in an initial cohort of patients.

METHODS

We used magnetic resonance imaging (MRI) from the Human Connectome Project (HCP) to create subject-specific target structures consisting of hippocampus, amygdala, and piriform/entorhinal/perirhinal cortex. An algorithm searched for safe potential trajectories along the hippocampal axis (catheter one) and along the amygdala-piriform axis (catheter two) and compared this to a single trajectory optimized over all structures. The proportion of each structure ablated at various burn radii was evaluated. A cohort of 11 consecutive patients with mTLE received two-trajectory LITT; demographic, operative, and outcome data were collected.

RESULTS

The two-trajectory approach was superior to the one-trajectory approach at nearly all burn radii for all hippocampal subfields and amygdala nuclei (p < .05). Two-laser trajectories achieved full ablation of MTL cortical structures at physiologically realistic burn radii, whereas one-laser trajectories could not. Five patients with at least 1 year of follow-up (mean = 21.8 months) experienced Engel class I outcomes; 6 patients with less than 1 year of follow-up (mean = 6.6 months) are on track for Engel class I outcomes.

SIGNIFICANCE

Our anatomic analyses and initial clinical results suggest that LITT amygdalohippocampotomy performed via two-laser trajectories may promote excellent seizure outcomes. Future studies are required to validate the long-term clinical efficacy and safety of this approach.