Article
One session stereotactic biopsy and stepping source interstitial irradiation in glioblastoma – a technical feasibility study and novel radiotherapy planning algorithm
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Authors
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Stefanie Brehmer
- Klinik für Neurochirurgie, Universitätsmedizin Mannheim, Medizinische Fakultät Mannheim der Universität Heidelberg, Germany
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Christian Guthier
- Experimentelle Strahlentherapie, Universitätsmedizin Mannheim, Medizinische Fakultät Mannheim der Universität Heidelberg, Germany
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Dirk Michael Schulte
- Klinik für Neurochirurgie, Universitätsmedizin Mannheim, Medizinische Fakultät Mannheim der Universität Heidelberg, Germany
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Daniel Hänggi
- Klinik für Strahlentherapie, Universitätsmedizin Mannheim, Medizinische Fakultät Mannheim der Universität Heidelberg, Germany
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Frederik Wenz
- Klinik für Strahlentherapie, Universitätsmedizin Mannheim, Medizinische Fakultät Mannheim der Universität Heidelberg, Germany
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Frank Anton Giordano
- Klinik für Strahlentherapie, Universitätsmedizin Mannheim, Medizinische Fakultät Mannheim der Universität Heidelberg, Germany
| Published: | June 8, 2016 |
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Outline
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Objective: Patients diagnosed with glioblastoma (GBM) receiving stereotactic biopsy (STX) due to localization or clinical status face a poor prognosis. Here a strategy to provide a local therapy could be interstitial radiation through the trajectory of the STX. Challenges for this approach are non-spherical tumors, where either sub-therapeutic doses at the tumor (gross tumor volume, GTV) or intolerable doses to adjacent risk structures (brain stem, optical nerve) may occur. Here, we tested technical feasibility of combination of STX and stepping-source interstitial radiation in a body donor. Thereafter, theoretical treatment was performed for a patient with a midline-crossing GBM infiltrating the splenium of the corpus callosum and both lateral ventricles.
Method: We performed two test procedures with a biopsy needle and a radiation source in a stereotactic phantom and then in a body donor using a MHT stereotactic system and a mobile intraoperative radiotherapy device (INTRABEAM, Carl Zeiss Meditec AG) to demonstrate the stability of the system in superficial and deep-seated lesions. First, accuracy was assessed using matched CT-scans. Second radiation treatment was exemplary planned for a patient with a midline-crossing elliptic GBM. To this we planned a trajectory for biopsy crossing the center of mass. Next, radiotherapy was planned though the same trajectory with the source located in the center of the lesion. Isodoses were calculated for the GTV and the brain stem as adjacent risk structure. A second calculation was then performed for the probe being stepped along the trajectory.
Results: Our novel setup resulted in no deviations between the target points reached with the biopsy needle and the radiation probe. We saw stability of superficial and deep trajectories, both in phantom and body donor studies. With our novel radiation treatment planning algorithm we could show that, if a highly effective and tumor-sterilizing dose of 30Gy should cover 100% of the GTV, fixed-source radiation in the center of the lesion will result in 100% (30Gy) brain stem dose, exceeding its tolerance limit of 12Gy. In contrast, the brain stem dose could be efficiently reduced with stepping-source radiation to 38% of the prescribed dose (11.4Gy), which is tolerable to the brain stem.
Conclusions: Our novel setup with stepping-source radiation using the trajectory of STX provides a robust basis for a clinical proof-of-concept trial and may widen treatment options for selected patients.
