Treatment outcomes of radiotherapy for primary spinal cord glioma

Purpose: Spinal cord gliomas are rare, and there is no consensus on the optimal radiotherapy (RT) regimen. Herein, we investigated therapeutic outcomes in spinal cord gliomas to obtain clues for the optimal RT regimen. Methods: We assessed 45 patients who received RT for primary spinal cord non-ependymoma gliomas between 2005 and 2017: 37 (82%) received postoperative RT, 6 (13%) underwent definitive RT without surgery, and 2 (5%) received salvage RT for recurrent tumors. Craniospinal irradiation (CSI; median, 40 Gy) was administered in 4 patients with seeding at diagnosis; all other patients received local RT only (median, 50.4 Gy). Results: In all 23 failures occurred (20 in patients without initial seeding +3 in patients with initial seeding and CSI; median follow-up, 33 months). The 2‑year overall survival and progression-free survival rates were 74 and 54%, respectively. Overall, 13 (32%) new seeding events outside the local RT field developed either first or subsequently. Tumor grade was significantly associated with survival endpoints (p = 0.009, 0.028) and overall seeding rates (p = 0.042). In grade II tumors, seeding developed in 23%, with a dismal prognosis (median, 10 months after RT). In grade III tumors, seeding developed in 45% with diverse prognosis. In grade IV tumors, seeding developed in 45%. The survival of patients with newly developed seeding was significantly worse than the others (2-year 50%, p < 0.001). Conclusion: To encompass a considerable rate of progressive disease seeding, aggressive treatment such as pre-emptive application of CSI needs to be considered for high-grade spinal cord gliomas with adverse features. Prophylactic CSI could be an option for survival prolongation and requires prospective validation.