In patients with ileal neuroendocrine tumours (ileal-NETs), head-to-head evaluation of diagnostic performances of 68 Ga-DOTA-peptides and 18 F-fluorodihydroxyphenylalanine (18 F-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.All patients with ileal-NETs who underwent both 18 F-FDOPA and 68 Ga-DOTATOC PET/CT within a 3-months period and no therapeutic change between the 2 studies were retrospectively included. The detection rates of both modalities were calculated using per-patient, per-region, and per-lesion analyses.41 patients with ileal-NETs were evaluated. 18 F-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=0.35). 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, 18 F-FDOPA PET/CT performed better than 68 Ga-DOTATOC PET/CT (overall detection rates of 96% vs. 80%; p<0.001). 18 F-FDOPA PET/CT detected significantly more metastases than 68 Ga-DOTATOC PET/CT in the liver, peritoneum, abdominal and supra diaphragmatic lymph nodes.18 F-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, 18 F-FDOPA should be considered as a valid clinical diagnostic option for exhaustive metastatic assessment in patients with ileal-NETs. Obviously, 68 Ga-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.

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