A case report of pseudoprogression followed by complete remission after proton-beam irradiation for a low-grade glioma in a teenager: the value of dynamic contrast-enhanced MRI

Abstract

A fourteen years-old boy was treated post-operatively with proton therapy for a recurrent low-grade oligodendroglioma located in the tectal region. Six months after the end of irradiation (RT), a new enhancing lesion appeared within the radiation fields. To differentiate disease progression from radiation-induced changes, dynamic susceptibility contrast-enhanced (DSCE) MRI was used with a T2* sequence to study perfusion and permeability characteristics simultaneously. Typically, the lesion showed hypoperfusion and hyperpermeability compared to the controlateral normal brain. Without additional treatment but a short course of steroids, the image disappeared over a six months period allowing us to conclude for a pseudo-progression. The patient is alive in complete remission more than 2 years post-RT.

Figure 1

Conventional MR imaging, Target volume and Dosimetry of a Low-grade Glioma. A left thalamic low-grade oligodendroglioma in a 10 year-old boy after partial resection, without contrast enhancement. [A] T1-weighted transaxial MR image after administration of intravenous Gd-DTPA [B] T2 -weighted sequence which shows ill-defined nodular images. [C] Representation of Gross tumor volume (in red) and Clinical target volume (in green). [D] Radiation field encompassing medial part of the left thalamus.

Figure 2

Conventional MR imaging before and six months after exclusive Proton therapy. [A] T1-weighted transaxial MR image after administration of intravenous (iv) Gd-DTPA, one week before radiation. [B] The same sequence, six months after the end of irradiation (54 Gy), showing a strong contrast enhancement with a subtle mass effect (yellow arrow).

Figure 3

Six months after irradiation: superimposed MR images with T1-weighted sequence after iv Gadolinium injection and co-registered Perfusion (left) and Permability maps (right). [A] Gradient-echo axial image with color overlay map showing no focus of hyperperfusion in regard of the strong contrast enhancement [B] The superimposed Permeability map with a strong microvascular leakage (yellow arrow) strictly corresponding with the enhanced area in the T1-weighted sequence.

Figure 4

Nine months after irradiation: complete disappearance of the contrast enhancement (left) and no detectable Permeability (right). [A] T1-weighted transaxial MR image after administration of iv Gd-DTPA and [B] the superimposed Permeability map, with no contrast enhancement or detectable microvascular leakage. To be noted, a subtle hypersignal, pre-existing to the irradiation, as a post-operative modification (yellow arrow).