Evaluation of Target Definition for Stereotactic Reirradiation of Recurrent Glioblastoma

Background and purpose: Glioblastoma multiforme (GBM) constitute the most prevalent brain tumor in adults. The prognosis of GBM is typically bleak, with eventual recurrence in an overwhelming majority of the patients despite multimodality management including surgery, radiation therapy (RT), and systemic treatment. Vast majority of patients develop recurrence within or in close vicinity of the initial RT field, which limits the reirradiation dose to be delivered for recurrent tumor. Accurate target definition is critical for stereotactic reirradiation of recurrent glioblastoma. Multimodality imaging with computed tomography (CT), magnetic resonance imaging (MRI) and molecular imaging techniques may be used for detection of recurrence. In this study, we assessed the utility of multimodality imaging in target volume determination for stereotactic reirradiation of recurrent glioblastoma. Patients and methods: Sixteen patients receiving radiosurgery at our institution for recurrent glioblastoma were identified for comparative evaluation of target definition based on CT imaging only and CT-MR fusion based imaging. Results: CT-only imaging and CT-MR fusion based imaging for radiosurgery target definition was comparatively evaluated for 16 patients treated with radiosurgery at our institution for recurrent glioblastoma. Comparative assessment revealed that target definition based on CT-MR fusion based imaging was optimal and identical to the consensus decision of treating physicians in majority of the treated patients. Conclusion: Incorporation of MRI may improve target definition for recurrent glioblastoma radiosurgery despite the need for further supporting evidence.