Presentation of treatment effect in glioblastoma after dose-escalation radiation therapy.

Glioblastoma is the most aggressive primary brain tumor in adults. Limited treatment options and the intense nature of therapy make determining the appropriate treatment course for each patient difficult. The appearance of transient worsening of imaging findings, known as treatment effect, after chemoradiation further complicates clinical decision-making. Accurately differentiating treatment effects from true progression is critical as subsequent treatment decisions are based largely on radiographic evidence of tumor progression. As chemoradiation can cause worsening of imaging findings, it is possible that the use of new treatments and modified chemoradiation regimens may alter the presentation of treatment effect. Therefore, physicians should be aware that atypical presentations of treatment effects can occur, and may be more likely, when treatment regimens are modified. Here, we present the case of a patient with isocitrate dehydrogenase 1 wild type, O-6-methylguanine-DNA methyltransferase-methylated glioblastoma who underwent dose-escalation radiation therapy (to 75 Gy) and exhibited worsened imaging findings at 8 months post-radiation.