Intraindividual comparison of18F-FDOPA and68Ga-DOTATOC PET/CTdetection ratefor metastatic assessment in patients with ileal neuroendocrine tumours

Introduction In patients with ileal neuroendocrine tumours (ileal NETs), head-to-head evaluation of diagnostic performances of(68)Ga-DOTA-peptides and(18)F-fluorodihydroxyphenylalanine (F-18-FDOPA) positron emission tomography/computed tomography (PET/CT) has been performed in only few small patients' cohorts. The aim of this retrospective study was to compare(68)Ga-DOTATOC and(18)F-FDOPA PET/CT for metastatic disease assessment in a homogeneous large series of patients with well-differentiated ileal NETs. Methods All patients with ileal NETs who underwent both(18)F-FDOPA and(68)Ga-DOTATOC PET/CT within a 3-month period and no therapeutic change between the two studies were retrospectively included. The detection rates of both modalities were calculated using per-patient, per-region and per-lesion analyses. Results Forty one patients with ileal NETs were evaluated.F-18-FDOPA and(68)Ga-DOTATOC showed similar detection rates according to per-patient (97% for both) and per-region analyses (94% for(18)F-FDOPA vs 88% for(68)Ga-DOTATOC,P = .35). For a total of 605 positive lesions, 458 (76%) were detected by both modalities, 122 (20%) exclusively by(18)F-FDOPA PET/CT, and 25 (4%) by(68)Ga-DOTATOC PET/CT only. In a per-lesion analysis,F-18-FDOPA PET/CT performed better than(68)Ga-DOTATOC PET/CT (overall detection rates of 96% vs 80%;P < .001).F-18-FDOPA PET/CT detected significantly more metastases than(68)Ga-DOTATOC PET/CT in the liver, peritoneum, abdominal and supra-diaphragmatic lymph nodes. Conclusion F-18-FDOPA PET/CT seems not inferior than(68)Ga-DOTATOC PET/CT for the delineation of metastatic spread of ileal NETs. Therefore, according to local expertise and technical availability,F-18-FDOPA should be considered as a valid clinical diagnostic option for exhaustive metastatic assessment in patients with ileal NETs. Obviously,Ga-68-DOTATOC PET/CT remains mandatory for PRRT assessment. Further comparative studies are needed to determine the optimal approach in various clinical scenarios such as preoperative staging and primary tumour detection.