RDTA-17 STEREOTACTIC RADIOSURGERY FOR BRAINSTEM METASTASES - A RETROSPECTIVE STUDY FROM A SINGLE INSTITUTION

Abstract BACKGROUND Brainstem metastases (BSM) are relatively rare, accounting for approximately 3–7% of all brain metastases. The pons is the most common site for BSM, followed by the midbrain and medulla oblongata. Despite their rarity, BSM are linked to poor prognosis. No standard therapeutic guidelines exist for this setting. BSM pose significant treatment challenges due to critical neural structures, making surgery and early radiation therapies high-risk. While WBRT was traditionally used, Stereotactic radiosurgery (SRS) has emerged as a pivotal non-invasive treatment for brain metastases. METHODS We retrospectively reviewed cases of BM in brainstem treated with SRS at our institute from 2000 to 2024. A total of 98 lesions from 88 patients were included. The study aims to evaluate overall survival, along with local tumor control (LTC) and symptoms resolution. Survival outcomes were assessed using Kaplan-Meier analysis. RESULTS The median age at diagnosis of BSM was 62.5 years (IQR:51.5-68). The most common primary tumors were NSCLC (42.0%), breast cancer (19.3%), and melanoma (10.2%). The median target volume was 0.4 cc (IQR: 0.08-1.96 cc). The median prescribed dose delivered was 20 Gy (IQR: 20-24 Gy). The median Overall survival was 10 months (95% CI: 8.2 to 11.6). Symptom resolution after SRS was observed in 82.5% of patients. The cumulative 6-months, 12-months, and 24-months local control rates were 97.3%, 94.8%, and 92.3%, respectively. The overall survival rates were 69% at 6 months, 44.7% at 12 months, 44.7% at 16 months, and 34% at 24 months. CONCLUSION SRS provides effective local tumor control for BSM, with high cumulative local control rates. Despite the challenging location, symptom resolution was achieved in 82.5% of symptomatic patients, highlighting the potential palliative benefits of SRS. These findings support SRS as a safe and effective treatment option for BSM, though further studies are needed to optimize long-term outcomes.