497 Superficial MRI-guided Laser Interstitial Thermal Therapy (LITT) for Intracranial Metastasis Is Associated With a Significantly Higher Rate of Leptomeningeal Disease

INTRODUCTION: Evolving brain metastases treatment standards has led to shifting intracranial recurrence patterns, especially with respect to pachymeningeal and leptomeningeal disease (PMD/LMD). As an emerging technique, it remains unclear if the depth of magnetic resonance imaging-guided laser interstitial thermal therapy (LITT) is associated with frequency of iatrogenic PMD/LMD. METHODS: A single-institute retrospective analysis of patients who underwent LITT surgery between 2014 and 2022 was conducted to investigate the development of PMD/LMD. P-values <0.05 were considered statistically significant. RESULTS: Eleven patients undergoing thirteen LITT procedures were analyzed. Mean age was 62.6 (±11.7), and 69.2% of patients were female. PMD/LMD developed in 4/13 cases (30.8%). There was no significant difference between superficial vs. deep LITT ablation in terms of age, sex, follow-up time, and primary cancer site. Superficial LITT ablation had a significantly higher frequency of PMD/LMD compared to deep LITT ablation (p = 0.02). Time to PMD/LMD development among patients who underwent superficial LITT ablation was significantly shorter compared to that among patients who had deep LITT ablation (p = 0.02). CONCLUSIONS: Superficial LITT ablation was associated with significantly higher frequency and shorter time to PMD/LMD development compared to deep LITT ablation. These results suggest that iatrogenic PMD/LMD spread during superficial LITT ablation may increase the proportion of PMD/LMD and accelerate disease timeline.