In Canada, staging of carcinoid tumors is largely based on computed tomography (CT) imaging sometimes complemented with somatostatin receptor scintigraphy (SRS). This study assessed the diagnostic accuracy of 6-[18F]fluoro-3,4-dihydroxyphenylalanine (18F-FDOPA) PET/CT in neuroendocrine tumors.
We prospectively included 27 patients with either suspected carcinoid (n=6, with all prior tests negative) or with an established diagnosis of intestinal carcinoid tumor (n=21) from two Canadian treatment centers. Findings of 18F-FDOPA PET/CT were compared with SRS, CT, and combined SRS/CT using a composite reference standard comprising all available imaging, biochemistry, surgery, and follow-up data. Sensitivity was calculated per patient, per body region, and per lesion. The contribution to patient management was estimated from the feedback of attending physicians.
In documented carcinoid patients, 18F-FDOPA PET/CT identified disease in 20 of 21 patients (patient-based sensitivity 95%). In 56 positive regions, 18F-FDOPA PET/CT detected 53, CT detected 34, SRS detected 34, and CT+SRS detected 39 regions, leading to region-based sensitivities of 95, 61, 62, and 71%, respectively. Lesion-based sensitivities were 96, 69, 50, and 72%, respectively. In the six patients with suspected disease only, one CT scan was positive, but 18F-FDOPA PET/CT was negative for all. 18F-FDOPA PET contributed to patient management in 12/21 patients (57%).
18F-FDOPA PET/CT proved to be an excellent modality for staging of carcinoid tumor patients, with superior performance compared with currently applied methods in Canada. In patients with suspected disease with negative prior imaging investigations, 18F-FDOPA was not helpful.