Bicentric Treatment Outcomes following Proton Therapy for Non-Myxopapillary High-Grade Spinal Cord Ependymoma in Children.

INTRODUCTION Few studies report outcomes in children treated with radiation for non-myxopapillary ependymoma of the spinal cord, and little evidence exists to inform decisions regarding target volume and prescription dose. Moreover, virtually no mature outcome data exist on proton therapy for this tumor. We describe our combined institutional experience treating pediatric classical/anaplastic ependymoma of the spinal cord with proton therapy. METHODS AND MATERIALS Between 2008 and 2019, 14 pediatric patients with non-metastatic non-myxopapillary grade II (n=6) and grade III (n=8) spinal ependymoma received proton therapy. The median age at radiation was 14 (range, 1.5-18) years old. Five tumors arose within the cervical cord, 3 within the thoracic cord, and 6 within the lumbosacral cord. Before radiotherapy, 3 patients underwent subtotal resection while 11 underwent gross-total or near total resection. Two patients received chemotherapy. For radiation, the clinical target volume received 50.4 Gy (n=8), 52.2 (n=1), or 54 Gy (n=5), with the latter receiving a boost to the gross tumor volume following the initial 50.4 Gy, modified to respect spinal cord tolerance. RESULTS With a median follow-up of 6.3 (range, 1.5 - 14.8) years, no tumors progressed. While most patients experienced neurologic sequela following surgery, only 1 developed additional neurologic deficits following radiation: An 18-year-old male who received 54 Gy after gross total resection of a lumbosacral tumor developed grade 2 erectile dysfunction. There were 2 cases of musculoskeletal toxicity attributable to surgery and radiation. At analysis, no patient had developed cardiac, pulmonary, or other visceral organ complications, nor a second malignancy. CONCLUSION Radiation to a total dose of 50-54 Gy can be safely delivered and plays a beneficial role in the multidisciplinary management of children with non-myxopapillary spinal cord ependymoma. Proton therapy may reduce late radiation effects and is not associated with unexpected spinal cord toxicity.