Combining 6-fluoro-[18F]l-dihydroxyphenylalanine and [18F]fluoro-2-deoxy-d-glucose positron emission tomography for distinction of non-carcinoid malignancies in carcinoid patients

AimCarcinoid patients frequently develop a second primary malignancy (SPM), which can deserve full treatment. Distinguishing a SPM from carcinoid lesions is therefore important. Differentiation can be achieved using the difference in uptake between different positron emission tomography (PET) tracers.Methods and resultsBetween January 2005 and August 2008, 105 carcinoid patients were seen at the Department of Medical Oncology for treatment and follow-up. We identified 3 patients who presented with a new SPM in whom differentiation between carcinoid lesions and the SPM was guided by functional imaging of the catecholamine pathway with 6-fluoro-[18F]l-dihydroxyphenylalanine (18F-DOPA) PET and [18F]fluoro-2-deoxy-d-glucose (18F-FDG) PET as radiotracer for the glucose metabolism. All 3 patients had metastatic carcinoid disease and localised adenocarcinoma based on the PET-scans. For the adenocarcinoma they received curative treatment.ConclusionThe difference in uptake between these PET techniques can be used for decision making when a primary or metastatic SPM is suspected.