Quantitative Volumetric Analysis Following Magnetic Resonance–Guided Laser Interstitial Thermal Ablation of Cerebellar Metastases

BACKGROUND: Treating recurrent posterior fossa metastases after previous radiation therapy and surgical resection remains challenging. Magnetic resonance laser-induced thermal therapy (MR-LITT) is a promising treatment for recurrent lesions, but data on safety, efficacy, and postablation volume change in the posterior fossa are lacking. METHODS: 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. RESULTS: 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 cm(3) (range, 1.1-7.2 cm(3)), and the average final postoperative volume was 3.8 cm(3) (range, 0.5-7.6 cm(3)). 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 cm(3) to final postoperative follow-up MRI of 3.4 cm(3) (P = 0.0952). No postoperative hydrocephalus or complications occurred. CONCLUSIONS: This pilot study shows that LITT appears to be a safe and promising treatment for recurrent posterior fossa metastatic lesions up to 7.2 cm(3). Further randomized controlled studies are warranted to further characterize the long-term efficacy of this therapy.