Fig 5.

Pseudoprogression in a 56-year-old man who underwent chemoradiation after gross total resection of a GBM in the left parietal lobe. A, Axial contrast-enhanced T1-weighted image obtained 1 week after an operation shows thin ring enhancement in the surgical bed (asterisk), which was considered to represent granulation tissue, related to the operation. The study was not obtained within the first 48 hours due to hemodynamic instability of the patient. B, Soon after completion of radiation therapy, the patient developed marked enhancement in the margins of the surgical cavity (arrow), with effacement of the adjacent sulci. In the following 3 months, he presented with progressive altered mental status and right-side hemiparesis. C, At that time, axial contrast-enhanced T1-weighted imaging showed an increase in mass effect, midline shift, with a slight increase in enhancement extension, which turned to a soap bubble appearance (arrowhead), a pattern typically associated with radiation necrosis. D, The patient improved clinically, and after 4 months, a new image depicted fading of the enhancing lesion (curved arrow) and a marked decrease in mass effect, which is the classic course of pseudoprogression.