Pseudoprogression in Pediatric Spinal Pilocytic Astrocytoma and Myxopapillary Ependymoma after Proton Therapy: A Case Series.

BACKGROUND

Little is known about pseudoprogression after proton therapy (PT) for pediatric spinal tumors. Clinical consequences are significant if it is not appropriately identified. We report the incidence of pseudoprogression in pediatric spinal pilocytic astrocytoma (sPA) and myxopapillary ependymoma (MPE) after PT at our institution.

PROCEDURE: Medical charts were retrospectively reviewed for patients <18 years old who received PT from 2007 to 2019 for sPA or MPE. Patients with gross disease at the time of PT and at least 6 months of follow-up were included. Demographic, tumor, and treatment characteristics were tabulated. Two neuroradiologists scored pre- and post-PT magnetic resonance images to assess for pseudoprogression, and the incidence of pseudoprogression was determined.

RESULTS

Fifteen patients were included (nine with sPA, six with MPE). Median age of patients with sPA was 10.1 years and 12.7 years for patients with MPE. Median prescribed dose was 45.0 cobalt-60 Gy equivalents (GyRBE) (range, 39.6-50.4) for sPA and 50.4 GyRBE for MPE (range, 45.0-54.0). Within 6 months post-PT, pseudoprogression occurred in six of nine patients (67%) with sPA, and three were symptomatic. No patients with MPE developed pseudoprogression (p < 0.03).

CONCLUSIONS

Pseudoprogression may occur within 6 months after PT for sPA but is not likely for MPE, even with a higher median PT dose. As pseudoprogression can be clinically challenging, clinicians should be aware of this possibility to provide appropriate guidance for patients and families.