P11.48.A STEREOTACTIC RADIOSURGERY FOR EPENDYMOMA IN PEDIATRIC AND ADULT PATIENTS: A SINGLE-INSTITUTION EXPERIENCE

Abstract

Abstract BACKGROUND Ependymoma is typically classified as WHO grade 2 and its anaplastic variant as grade 3. Despite standard treatment approaches, incomplete resection or anaplastic features can lead to poor prognosis. Stereotactic radiosurgery (SRS) is a promising minimally invasive option for recurrent ependymomas after surgery and radiation therapy. This study aims to evaluate the efficacy and safety of CyberKnife radiosurgery in treatment of WHO grade II versus III ependymomas in both pediatric and adult populations. MATERIAL AND METHODS In our study, we evaluated the clinical and radiological records of patients who underwent CyberKnife SRS for ependymoma at our institution between 1998 and 2023. The follow-up data were available for a total of 75 ependymomas in 34 patients. The study population consisted of 14 pediatric patients (ages 3-18) and 20 adult patients (ages 19-75). The median age was 21 years and the median tumor volume accounted for 0.64 cc. The median biologically equivalent dose (BED) and single-fraction equivalent dose (SFED) were 108 Gy and 16.6 Gy, respectively. The SRS was administered at the 77% of the median isodose line. RESULTS At a median follow-up of 42.7 months (range: 3.8-438.3) after treatment, our analysis revealed that only 17 (22.7%) ependymomas progressed. The 5-year local tumor control (5-yrs-LTC) rate for all ependymomas was 78.1%, with a lower rate of 59.6% observed in the pediatric cohort and a higher rate of 90.2% in adult patients. For ependymomas classified as WHO grade II, the 5-yrs-LTC rate was 85.9%, whereas it was 58.5% for those classified as WHO grade III. The 5-year overall survival (5-yrs-OS) rate was 73.6% for all patients, with significantly higher rates observed in pediatric patients (94.7%) than in adult patients (41%). The 5-yrs-OS rate was 100% for patients with WHO grade II tumors, whereas it decreased significantly to 35.9% for patients with WHO grade III ependymomas. The 5-year progression-free survival (5-yrs-PFS) rate was 68.5% for all patients, with higher rates observed in pediatric patients (78.3%) than in adult patients (49.2%). The 5-yrs-PFS rate for patients with WHO grade II lesions was 88.8%, whereas it was significantly lower at 32.6% for patients with WHO grade III tumors. Stereotactic radiosurgery (SRS) was effective in improving tumor-associated symptoms in 29 (85.3%) patients with 62 (82.7%) symptomatic ependymomas. These symptoms included headache, back pain, dizziness, nausea, vomiting, cranial nerve palsy, ataxia, motor impairment, sensory deficit, seizures, and weight loss. Notably, no patients developed adverse radiation effects. CONCLUSION CyberKnife SRS is a safe and effective treatment for ependymoma in both adults and children, with potential for significant improvements in tumor-related symptoms. Our study supports its use as a minimally invasive alternative to surgery, warranting further investigation.