Rdta-01 Navigating the Thalamus: Role of Stereotactic Radiosurgery in the Management of Brain Metastases - A Retrospective Study From a Single Institution

BACKGROUND Thalamus, known as the neural processor and integrator for forebrain activities, is an uncommon site for metastatic lesions. Stereotactic radiosurgery has become a key non-invasive treatment for BM. This study aims to assess the efficacy, safety, and clinical outcomes of SRS. METHODS We retrospectively reviewed cases of BM in thalamus treated with SRS at our institute between 2002 and 2024. A total of 49 lesions from 47 patients were included. Statistical analyses included Binomial Logistic Regression, Chi-square, Mann-Whitney U tests where appropriate, with survival outcomes assessed using Kaplan-Meier analysis. RESULTS The mean follow-up was 18.92 months. The median size of the BM was 1.0 cm (IQR: 0.50 - 1.95 cm) with the mean volume of 2 cm3. The median dose delivered was 22 Gy. Larger thalamic tumors are significantly associated with increased local recurrence (p = 0.025). Higher maximum radiation doses are significantly associated with reduced tumor recurrence (P= 0.042). ROC analysis revealed 24Gy to be the Dmax predictive of treatment response with AUC of 0.813 and sensitivity of 92.7%. Multivariate analysis revealed Dmax to be the only independent predictor of local tumor control (p=0.033). Pre-SRS thalamic aphasia (p = 0.028) is significantly associated with reduced symptom resolution following treatment. The cumulative 6-months, 9-months, 12-months and 24-months local control rates were 100%, 90%, 82.5%, and 77.6% respectively. The overall survival rates were 91.4% at 6 months, 89.1% at 12 months, 84.0% at 16 months, and 68.3% at 24 months, with a mean overall survival of 38.8 months (95% CI: 23.5 to 54.1). CONCLUSION Our results demonstrated sufficient local control, with SRS proving to be an effective and safe treatment for thalamic brain metastases, achieving high sustained cumulative control rates over time. Achieving a Dmax of 24 Gy may be predictive of better local tumor control for these complex pathologies.