Imaging Changes and Clinical Outcome after MR-Guided Laser Interstitial Thermal Therapy.

Abstract

Introduction: MR-guided laser interstitial thermal therapy (MRgLITT) is a minimally invasive technique for treating deep-seated brain lesions. However, the dynamics of imaging changes that occur after the ablation are not well characterized. This study aimed to describe the clinical outcomes and volume changes that occur over time after MRgLITT.

Methods: We retrospectively collected clinical and imaging data of all adult patients who underwent MRgLITT of brain tumors (primary and metastatic) between 01/2020 and 06/2024. Volumes and diameters of the lesions were measured on gadolinium-enhanced T1-weighted images using Brainlab Elements. Local control was assessed at the last follow-up.

Results: Twenty-nine patients with 32 treated lesions were available for assessment. Most lesions (n = 21) were metastatic, while 11 lesions were gliomas. The mean follow-up period was 23.4 ± 13.1 months. The average preoperative tumor volume was 2.8 ± 1.8cc. Post-ablation, the lesions' volumes increased on average by 250% (up to 450%) in the first month after surgery compared to the preoperative volumes. The enhancing ring extended distally beyond the tip of the catheter for an average of 4.5 ± 1.8 mm. Glial lesions had a median progression-free survival of 8.5 months. The volume of metastatic lesions decreased below the preoperative volume on average 3 months after surgery. Local control was achieved in 16 of 21 metastatic lesions (76%) and was significantly better for lesions smaller than 4cc in volume and 16 mm in maximal diameter that could be completely covered by the thermal damage estimation. Nodular enhancement at 3 months post-surgery was correlated with local failure.

Conclusion: MRgLITT can achieve good local control in metastatic brain lesions and should be considered early during follow-up after radiosurgery when local failure is suspected. The enhancing lesion extends beyond the tip of the catheter and enlarges during the first month post-ablation before gradually decreasing in size. Failure to decrease in size after 3 months or appearance of a nodular enhancement should raise suspicion of local failure.

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