Bicentric Treatment Outcomes After Proton Therapy for Nonmyxopapillary High-Grade Spinal Cord Ependymoma in Children

Abstract

Purpose: Few studies report outcomes in children treated with radiation for nonmyxopapillary 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 nonmetastatic nonmyxopapillary grade II (n = 6) and grade III (n = 8) spinal ependymoma received proton therapy. The median age at radiation was 14 years (range, 1.5-18 years). Five tumors arose within the cervical cord, 3 within the thoracic cord, and 6 within the lumbosacral cord. Before radiation therapy, 3 patients underwent subtotal resection, and 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 after the initial 50.4 Gy, modified to respect spinal cord tolerance.

Results: With a median follow-up of 6.3 years (range, 1.5-14.8 years), no tumors progressed. Although most patients experienced neurologic sequela after surgery, only 1 developed additional neurologic deficits after 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 or a second malignancy.

Conclusion: Radiation to a total dose of 50 to 54 Gy can be safely delivered and plays a beneficial role in the multidisciplinary management of children with nonmyxopapillary spinal cord ependymoma. Proton therapy may reduce late radiation effects and is not associated with unexpected spinal cord toxicity.