SURG-35. Steroid responsiveness, not surgical procedure, predicts recovery after LITT vs resection of primary motor cortex tumors

Abstract Laser interstitial thermal therapy (LITT) is uniquely situated to address radiographically progressive metastases after radiosurgery. Historically, open resection (OR) has been favored for eloquent area metastases given risk of thermal damage to white matter tracts. We retrospectively reviewed a single center cohort of patients undergoing either OR (n=39) or LITT (n=28) for motor cortex-associated brain metastases. Functional outcomes (Karnofsky performance status [KPS], modified Rankin Scale [mRS], and symptom status) were serially assessed to one year. A multivariate logistic regression model identified predictors of 30-day functional outcomes, the expected peak period for post-LITT edema. Volumetric tumor segmentations were obtained with deep learning-based segmentation and normalized to MNI space for lesion mapping. Patients undergoing LITT had smaller tumors (median 2.80 cm³ vs 7.27 cm³, P<0.0001) and more frequently had prior stereotactic radiosurgery (100% vs 51.28%, P<0.0001). OR was associated with greater ICU use (74.36% vs 17.86%, P<0.0001) and longer hospitalization (median 2 vs 1 days, P=0.0004). Functional outcomes (KPS, mRS, and symptom trajectory) did not differ between groups at discharge or at follow-up through one year, except for worse symptom stability at 30 days in the LITT cohort (56.00% vs 80.64%, P=0.046). Freedom from local progression did not significantly differ by procedure type (P=0.41). On multivariate analysis, the only significant predictor of favorable 30-day composite functional outcome was preoperative response to steroids (P=0.04), independent of lesion volume, pathology, systemic disease status, or procedure type. Our study shows that LITT is a safe, effective alternative to OR for motor cortex-associated brain metastases in carefully selected patients, offering shorter hospitalization and reduced ICU use. Functional outcomes are equivalent between LITT and OR at one year, despite transient post-ablation edema. Preoperative steroid response strongly predicts short-term functional recovery, suggesting it may serve as a simple, clinically actionable tool for patient selection in eloquent area LITT.