SURG-07. CORRELATION BETWEEN VOLUMETRIC ANALYSIS AND CLINICAL OUTCOMES OF BRAIN METASTASES TREATED WITH LASER INTERSTITIAL THERMAL THERAPY (LITT)

Abstract

PURPOSE: Describe and analyze the volumetric responses of metastatic brain tumors treated with LITT and how changes correlate with local recurrence (LR). MATERIALS AND METHODS: Retrospective study with consecutive patients with progressive disease after SRS for brain metastasis. Spider and scatter plots and Locally Weighed Scatterplot Smoothing (LOWESS) for tumor and edema volume were created to analyze volume changes. Patients were compared using Chi-square tests and odds ratios (OR). RESULTS: 61 consecutive patients with 82 lesions (5 newly diagnosed, 46 recurrence and 31 radiation necrosis). Mean tumor volume was 4.84cm3, mean edema volume was 43.86cm3 and the mean ablation volume was 8.09cm3. LOWESS showed an initial increase in the first month, followed by steady decrease in the following months. Tumor edema shows a plateau or a slight increase in the first month, followed by a steady decrease in the subsequent months. Patients with LR showed an increase in the edema in the first 60 days, whereas tumor volume tended to remain stable, increasing in size after the third/fourth month. After 60 days, if edema volume is above baseline or increasing in size from nadir, there is an increased risk of LR (OR 4.22; 95% CI 1.5011.89,P=0.0053). Tumor volume above baseline ablation volume or increasing from a nadir on the first scan after day 60 had an increased risk of recurrence (OR 3.46; 95% CI 1.239.71,P=0.0016). If both edema and tumor volume are above baseline or increasing after day 60, there is also an increased risk of LR (OR 4.00; 95% CI 1.4111.36,P=0.0077). CONCLUSIONS: If either edema or tumor volume fail to fall below baseline or show an increasing trend on the first scan after day 60 post LITT, patients have an increased risk of LR. Qualitatively edema was the first feature observed in LR followed by increase in tumor volume.