18F-FDOPA PET/CT Combined with MRI for Gross Tumor Volume Delineation in Patients with Skull Base Paraganglioma.

Mehdi Helali,Fabrice Hubelé,Céline Heimburger,Matthieu Moreau,Alessio Imperiale,Anne Charpiot,Bernard Goichot,Georges Noel,Caroline Bund,Clara Le Fèvre,Francis Veillon

doi:10.3390/cancers11010054

Abstract

In this simulation study, we assessed differences in gross tumor volume (GTV) in a series of skull base paragangliomas (SBPGLs) using magnetic resonance imaging (MRI), 18F-dihydroxyphenylalanine (18F-FDOPA) combined positron emission tomography/computed tomography (PET/CT), and 18F-FDOPA PET/MRI images obtained by rigid alignment of PET and MRI. GTV was delineated in 16 patients with SBPGLs on MRI (GTVMRI), 18F-FDOPA PET/CT (GTVPET), and combined PET/MRI (GTVPET/MRI). GTVPET/MRI was the union of GTVMRI and GTVPET after visual adjustment. Three observers delineated GTVMRI and GTVPET/MRI independently. Excellent interobserver reproducibility was found for both GTVMRI and GTVPET/MRI. GTVPET and GTVMRI were not significantly different. However, there was some spatial difference between the locations of GTVMRI, GTVPET, and GTVPET/MRI. The Dice similarity coefficient median value was 0.4 between PET/CT and MRI, and 0.8 between MRI and PET/MRI. The combined use of PET/MRI produced a larger GTV than MRI alone. Nevertheless, both the target-delivered dose and organs-at-risk conservancy were respected when treatment was planned on the PET/MRI-matched data set. Future integration of 18F-FDOPA PET/CT into clinical practice will be necessary to evaluate the influence of this diagnostic modality on SBPGL therapeutic management. If the clinical utility of 18F-FDOPA PET/CT and/or PET/MRI is confirmed, GTVPET/MRI should be considered for tailored radiotherapy planning in patients with SBPGL.

Highlights

Head and neck paragangliomas (HNPGLs) are rare and slow-growing tumors that result from paraganglia, neural crest-derived clusters of neuroendocrine cells
We evaluated the safety of irradiation therapy using PET/Magnetic resonance imaging (MRI) fusion images, and in selected patients, compared the radiation treatment planning and dosimetry obtained from gross tumor volume (GTV) assessed by MRI, which is the standard at several institutions, and PET/MRI-registered images
A p-value less than 0.05 was considered significant. In this era of multimodality imaging, we should consider that no single imaging modality encompasses an entire microscopic and macroscopic tumor, pointing out the difficulty selecting which imaging modality is superior for target volume delineation

Summary

Introduction

Head and neck paragangliomas (HNPGLs) are rare and slow-growing tumors that result from paraganglia, neural crest-derived clusters of neuroendocrine cells. HNPGLs account for about 70% of extra-adrenal PGLs and develop from parasympathetic paraganglia of the jugular bulb and carotid body, or along the tympanic branch of the glossopharyngeal nerve, the vagus nerve, and its auricular branch [1]. Magnetic resonance imaging (MRI) and MR angiography are very accurate for tumor detection and local extension definition [4]. Combined positron emission tomography and computed tomography (PET/CT) with 18 F-dihydroxyphenylalanine (18 F-FDOPA) is highly sensitive (91%) and specific (95%) and is currently proposed as the first-line nuclear imaging modality in HNPGLs both at staging and during the post-treatment follow-up [5,6,7]. In PGLs, 18 F-FDOPA uptake reflects the pathological up-regulation of the catecholamine biosynthetic pathway [8]

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Discussion

Conclusion