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.

Aim: Carcinoid 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 Results: Between 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-[(18)F]l-dihydroxyphenylalanine ((18)F-DOPA) PET and [(18)F]fluoro-2-deoxy-d-glucose ((18)F-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.

Conclusion: The difference in uptake between these PET techniques can be used for decision making when a primary or metastatic SPM is suspected.