Imaging Changes in Very Young Children with Brain Tumors Treated with Proton Therapy and Chemotherapy

N.D Sabin,J Gray,K Wright,T.E Merchant,D.J Indelicato,P Klimo,J.H Harreld,Z Patay,G.T Armstrong,I Qaddoumi,A Gajjar

doi:10.3174/ajnr.a3219

Abstract

PT promises to reduce side effects in children with brain tumors by sparing normal tissue compared with 3D conformal or intensity-modulated radiation therapy. Information is lacking about the combined effects of PT and chemotherapy in young children. We describe imaging changes in 8 very young children with localized brain tumors who received PT after chemotherapy. Mostly transient signal abnormalities and enhancement in brain parenchyma were observed by serial MR imaging, which were consistent with radiation-induced effects on normal-appearing tissue. Correlation with PT planning data revealed that the areas of imaging abnormality were located within or adjacent to the volume that received the highest radiation dose. Radiologists should be aware of these findings in children who receive PT after chemotherapy. In this report, we describe the time course of these PT-related imaging findings and correlate them with treatment and clinical outcomes.

Highlights

The imaging appearance of PT-related lesions in this series—mostly transient, T2 hyperintense enhancing lesions with associated T1 hypointensity and, in most cases, postgadolinium enhancement—is similar to that described in children treated with photon radiation therapy.[4,5,6,7] median and mean ages at diagnosis and treatment of the patients in our series, 1.8 and 2.4 years respectively, were much younger than the median ages of 7.1 years and 8.1 years at presentation in 2 of those series[6,7] and mean age of 5.4 years in 1 of those studies.[5] Median and mean times to lesion development in our series of children post-PT are shorter than the time to appearance of photon radiation therapy–related lesions, which have been reported to arise a median of 6 –10 months after the start or completion of radiation therapy.[4,5,6,7] The lesions in our series tended to regress sooner (1.5–3.5 months) than the time interval of 2–26 months described for patients treated with photons.[4,5,6,7] The differences in the time course may be related to the use of PT, the induction or maintenance chemotherapy regimen, the age of the patients included in our series,[8,9] or other factors coincident with the performance of the protocol, including surgical sequelae.[10,11,12]
Because clinical and MR evidence of radiation-related brain parenchymal changes within inimaging changes after PT are not well-documented, we describe tracranial tissue structures that demonstrated no abnormal signal or the time course of imaging changes associated with PT correlated enhancement before PT (Figs 1–3)
Eight of 17 young children with localized brain tumors treated with PT as part of a prospective protocol developed mostly transient imaging changes at a median time of 3.9 months and a mean time of 4.2 months after the completion of PT

Summary

Introduction

The imaging appearance of PT-related lesions in this series—mostly transient, T2 hyperintense enhancing lesions with associated T1 hypointensity and, in most cases, postgadolinium enhancement—is similar to that described in children treated with photon radiation therapy.[4,5,6,7] median and mean ages at diagnosis and treatment of the patients in our series, 1.8 and 2.4 years respectively, were much younger than the median ages of 7.1 years and 8.1 years at presentation in 2 of those series[6,7] and mean age of 5.4 years in 1 of those studies.[5] Median and mean times to lesion development in our series of children post-PT are shorter than the time to appearance of photon radiation therapy–related lesions, which have been reported to arise a median of 6 –10 months after the start or completion of radiation therapy.[4,5,6,7] The lesions in our series tended to regress sooner (1.5–3.5 months) than the time interval of 2–26 months described for patients treated with photons.[4,5,6,7] The differences in the time course may be related to the use of PT, the induction or maintenance chemotherapy regimen, the age of the patients included in our series,[8,9] or other factors coincident with the performance of the protocol, including surgical sequelae.[10,11,12]

Results

Conclusion