P11.50.A STEREOTACTIC RADIOSURGERY FOR RECURRENT MEDULLOBLASTOMA IN PEDIATRIC AND ADULT PATIENTS: A SINGLE-INSTITUTION EXPERIENCE

Abstract

Abstract BACKGROUND Medulloblastoma is the most common malignant brain tumor in children. In recent decades, the therapeutic landscape has undergone significant changes, with stereotactic radiosurgery (SRS) emerging as a promising modality for the treatment of recurrent medulloblastoma. Our study aims to provide a comprehensive long-term analysis of the efficacy and safety of SRS for both pediatric and adult patients with recurrent medulloblastomas at a single institution. MATERIAL AND METHODS In our study, we retrospectively reviewed the clinical and radiological records of patients who underwent CyberKnife SRS for medulloblastoma at our institution between 1998 and 2023. Clinical and radiographic follow-up data were available for a total of 15 medulloblastomas in 10 patients. The study population consisted of 8 pediatric patients (ages 3-18) and 2 adult patients (ages 19-75). The median age at the time of SRS was 13 years and the median tumor volume accounted for 1.88 cc. The median biologically equivalent dose (BED) and single-fraction equivalent dose (SFED) were 126 Gy and 18 Gy, respectively. The SRS was administered at the 75% of the median isodose line. RESULTS Following a median follow-up of 39 months (range: 6-78) post-treatment, 8 (53.3%) of the medulloblastomas progressed, 2 (13.3%) showed radiographic regression, and 5 (33.3%) remained stable in volume. The 3-year local tumor control rate for all medulloblastomas was 65.2%, with lower rates observed in the adult cohort (50%) and higher rates in pediatric patients (67.3%). The 3-year overall survival rate was 70%, with significantly higher rates in pediatric patients (75%) compared to adult patients (50%). The 3-year progression-free survival rate was 58.3%, with higher rates in pediatric patients (60%) compared to adult patients (50%). Two pediatric patients developed radiation-induced edema, while two adult patients experienced radiation necrosis at the latest follow-up, with both adult patients passing away. CONCLUSION SRS is a safe and effective long-term treatment option for recurrent medulloblastoma in both pediatric and adult patients, resulting in improved patient outcomes. Although rare, radiation-induced edema and necrosis were observed as adverse events but were manageable. Overall, our findings provide optimistic evidence for the use of SRS as a viable treatment modality for medulloblastoma.