Abstract
PurposeThe observation that human meningioma cells strongly express somatostatin receptor (SSTR 2) was the rationale to analyze retrospectively in how far DOTATOC PET/CT is helpful to improve target volume delineation for intensity modulated radiotherapy (IMRT).Patients and MethodsIn 26 consecutive patients with preferentially skull base meningioma, diagnostic magnetic resonance imaging (MRI) and planning-computed tomography (CT) was complemented with data from [68Ga]-DOTA-D Phe1-Tyr3-Octreotide (DOTATOC)-PET/CT. Image fusion of PET/CT, diagnostic computed tomography, MRI and radiotherapy planning CT as well as target volume delineation was performed with OTP-Masterplan®. Initial gross tumor volume (GTV) definition was based on MRI data only and was secondarily complemented with DOTATOC-PET information. Irradiation was performed as EUD based IMRT, using the Hyperion Software package.ResultsThe integration of the DOTATOC data led to additional information concerning tumor extension in 17 of 26 patients (65%). There were major changes of the clinical target volume (CTV) which modify the PTV in 14 patients, minor changes were realized in 3 patients. Overall the GTV-MRI/CT was larger than the GTV-PET in 10 patients (38%), smaller in 13 patients (50%) and almost the same in 3 patients (12%). Most of the adaptations were performed in close vicinity to bony skull base structures or after complex surgery. Median GTV based on MRI was 18.1 cc, based on PET 25.3 cc and subsequently the CTV was 37.4 cc. Radiation planning and treatment of the DOTATOC-adapted volumes was feasible.ConclusionDOTATOC-PET/CT information may strongly complement patho-anatomical data from MRI and CT in cases with complex meningioma and is thus helpful for improved target volume delineation especially for skull base manifestations and recurrent disease after surgery.
Highlights
Meningiomas represent about 20% of all intracranial brain tumors and are the most frequent nonglial brain tumors in adults with a clear predomination in women (f/m 2:1) [1]
There were major changes of the clinical target volume (CTV) which modify the planning target volume (PTV) in 14 patients, minor changes were realized in 3 patients
Overall the GTVMRI/computed tomography (CT) was larger than the gross tumor volume (GTV)-positron emission tomography (PET) in 10 patients (38%), smaller in 13 patients (50%) and almost the same in 3 patients (12%)
Summary
Meningiomas represent about 20% of all intracranial brain tumors and are the most frequent nonglial brain tumors in adults with a clear predomination in women (f/m 2:1) [1]. Adjuvant radiotherapy (RT) can improve local tumor control and overall survival after incomplete surgical resection [5,6,7,8]. Similar to numerous different malignancies treated with intensitymodulated RT [11,12,13], recently several IMRT based protocols for meningiomas have been issued offering even higher target volume conformity and improved normal tissue protection [14,15,16,17,18,19]. In general the use of highly conformal treatment techniques mandates improved pretherapeutic imaging. In this regard, positron emission tomography (PET) based techniques as well as other functional imaging modalities including SPECT-CT or MRI enter the routine in radiation oncology [2026]
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