The Role of Adjuvant Radiotherapy Dose in the Long Term Management of Primary Spinal Cord Ependymomas Winward Choy; Won Kim MD; Daniel Nagasawa BA; Marko Spasic MD; Antonio A. F. De Salles MD, PhD; Isaac Yang MD UCLA Neurosurgery UCLA Jonsson Comprehensive Cancer Center David Geffen School of Medicine at UCLA Introduction Spinal ependymoms are neuroepithelial tumors that represent the most common adult subtype of primary spinal cord tumors. Standard treatment comprises gross total resection when possible or subtotal surgical resection followed by adjuvant radiotherapy. However, dose guidelines for radiotherapy are not well characterized. Here we analyze the dose dependent- treatment outcomes of patients treated with postsurgical radiotherapy with long term follow-up. Methods To identify all reports of patients with primary spinal ependymomas, we performed a comprehensive PubMed search using Keywords “Spinal ependymoma and radiotherapy” and “Spinal ependymoma and Radiation therapy.” Patients were excluded if radiation dose (Gy) was not specified, if treated with radiation therapy alone, or if clinical follow up data regarding progression free or overall survival was absent. Patients were divided into groups receiving total doses of 50 Gy or less and greater than 50 Gy, and all accessible data were aggregated and analyzed. Results Overall, a total of 422 patients met our inclusion criteria. 112 patients received and average total dose of 50 Gy or less while 310 patients received and average total dose greater than 50 Gy. For all patients, average 5 and 10 year progression free survival (PFS) was 79.9% and 68.4%, respectively and 5 and 10 year overall survival (OS) was 89.1% and 80.5%, respectively. Adjuvant radiation therapy dose following surgical resection of the tumor for all patients ranged from 20 to 66 Gy. 5 and 10 year PFS for patients receiving surgical resection followed by adjuvant radiation therapy of less than 50 Gy 79.4% and 69.8%. For patients receiving adjuvant radiation therapy greater than 50 Gy, 5 and 10 year PFS was 82.7% and 66.3%. Additionally, radiotherapy with average total dose of 50 Gy or less was associated with slightly better 5 and 10 year OS (90.1% and 82.4%) than those receiving greater than 50 Gy (84.3% and 70.7%). Figure 1: Effect of high and low radiotherapy dose on 5-yr PFS. N=71 and N= 228 respectively (P= .055). Figure 2: Effect of high and low radiotherapy dose on 10-yr PFS. N=99 and N= 200 respectively (P= .091). Figure 3: Effect of high and low radiotherapy dose on 5-yr OS. N=53 and N= 231 respectively (P< .001). Figure 4: Effect of high and low radiotherapy dose on 10-yr OS. N=37 and N= 212 respectively (P< .001). Conclusions While radiotherapy following surgical resection may offer better tumor control for spinal ependymomas, our data suggests that high doses greater than 50 Gy do not necessarily confer an added benefit over those receiving doses of 50 Gy or less. A lower dose was associated wtih improved OS. Further prospective trials will be necessary to identify the optimal dosing to achieve both maximal clinical efficacy and safety. Learning Objectives -To identify optimal treatments for spinal ependymoma -To assess that higher doses of radiotherapy may not be associated with improved outcomes References: 1.Abdel-Wahab, M., et al., Spinal cord gliomas: A multi- institutional retrospective analysis. International journal of radiation oncology, biology, physics, 2006. 64(4): p. 1060-71. 2.Akyurek, S., et al., Spinal myxopapillary ependymoma outcomes in patients treated with surgery and radiotherapy at M.D. Anderson Cancer Center. Journal of neuro-oncology, 2006. 80(2): p. 177-83. 3.Clover, L.L., M.B. Hazuka, and J.J. Kinzie, Spinal cord ependymomas treated with surgery and radiation therapy. A review of 11 cases. American journal of clinical oncology, 1993. 16(4): p. 350-3. 4.Garcia, D.M., Primary spinal cord tumors treated with surgery and postoperative irradiation. International journal of radiation oncology, biology, physics, 1985. 11(11): p. 1933-9. 5.Ferrante, L., et al., Intramedullary spinal cord ependymomas--a study of 45 cases with long-term follow-up. Acta neurochirurgica, 1992. 119(1-4): p. 74-9. 6.Volpp, P.B., et al., Outcomes in treatment for intradural spinal cord ependymomas. International journal of radiation oncology, biology, physics, 2007. 69(4): p. 1199-204.