Cerebral cortex dose sparing for glioblastoma patients: IMRT versus robust treatment planning
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RESEARCH
Open Access
Cerebral cortex dose sparing for glioblastoma patients: IMRT versus robust treatment planning Ann-Katrin Exeli1*, Daniel Kellner2, Lukas Exeli1, Phil Steininger2, Frank Wolf1, Felix Sedlmayer1,2 and Heinz Deutschmann1,2
Abstract Background: To date, patients with glioblastoma still have a bad median overall survival rate despite radiation dose-escalation and combined modality treatment. Neurocognitive decline is a crucial adverse event which may be linked to high doses to the cortex. In a planning study, we investigated the impact of dose constraints to the cerebral cortex and its relation to the organs at risk for glioblastoma patients. Methods: Cortical sparing was implemented into the optimization process for two planning approaches: classical intensity-modulated radiotherapy (IMRT) and robust treatment planning. The plans with and without objectives for cortex sparing where compared based on dose-volume histograms (DVH) data of the main organs at risk. Additionally the cortex volume above a critical threshold of 28.6 Gy was elaborated. Furthermore, IMRT plans were compared with robust treatment plans regarding potential cortex sparing. Results: Cortical dose constraints result in a statistically significant reduced cerebral cortex volume above 28.6 Gy without negative effects to the surrounding organs at risk independently of the optimization technique. For IMRT we found a mean volume reduction of doses beyond the threshold of 19%, and 16% for robust treatment planning, respectively. Robust plans delivered sharper dose gradients around the target volume in an order of 3 – 6%. Aside from that the integration of cortical sparing into the optimization process has the potential to reduce the dose around the target volume (4 – 8%). Conclusions: We were able to show that dose to the cerebral cortex can be significantly reduced both with robust treatment planning and IMRT while maintaining clinically adequate target coverage and without corrupting any organ at risk. Robust treatment plans delivered more conformal plans compared to IMRT and were superior in regards to cortical sparing. Keywords: Radiotherapy, Robust treatment planning, IMRT, Glioblastoma, Cortex, Cortical sparing
Background Glioblastoma multiforme (GBM) is a highly malignant brain tumor with poor prognosis. With surgical resection alone the median survival amounts 6 months [1]. Today the gold standard treatment is based on a multidisciplinary approach employing surgery with maximal safe resection followed by radiotherapy with daily concomitant temozolomide [2] * Correspondence: [email protected] 1 Department of Radiotherapy and Radio-Oncology at the University Hospital Salzburg, Landeskrankenhaus, Paracelsus Medical University, 5020 Salzburg, Austria Full list of author information is available at the end of the article
followed by additional cycles of temozolomide. The overall survival with the combined modality treatment is in the range of 27% at 2 years and 10% at 5 years [3]. With the growing number of long term survivors it
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