Pseudoprogression after radiation therapies for low grade glioma in children and adults: A systematic review and meta-analysis

Background: Pseudoprogression (PsP) following radiation therapy (RT) for low grade glioma (LGG, WHO grade I and II), including both photon-based intensity-modulated RT (IMRT) and proton beam therapy (PBT), has been described. However, its incidence has yet to be consolidated. The aim of this systematic review and meta-analysis was to pool the current literature and establish the incidence of PsP in these groups to better inform surveillance protocols in the future. Methods: Searches of 4 electronic databases from inception to April 2019 were conducted following PRISMA guidelines. Articles were screened against pre-specified criteria. The incidence of outcomes was then extracted and pooled by random-effects meta-analysis of proportions. Results: A total of 5 pediatric and 4 adult cohort studies describing 517 and 424 LGG subjects respectively satisfied all selection criteria. The estimated incidences of PsP in pediatric subjects following IMRT and PBT were 33% (95% CI, 20-47%) and 34% (95% CI, 23-45%) respectively, with no difference between modalities. The estimated incidences of PsP in adult subjects following IMRT and PBT were 18% (95% CI, 12-25%) and 30% (95% CI, 21-39%) respectively, with PsP significantly less common following IMRT than PBT (P-heterogeneity = 0.04). Median time from radiation initiation to first detection of PsP ranged from 6 to 12 months across all modalities and age groups. Conclusions: The incidence of PsP following both IMRT and PBT in the management of pediatric and adult LGG is not negligible, and should therefore be recognized as a pertinent sequala within the first year at least following treatment. However, a lack of accountability in the current literature for the differences in PsP interpretation, radiation modality, radiobiology and molecular biology of LGGs precludes any firm surveillance recommendations at this time. (C) 2019 Elsevier B.V. All rights reserved.