The diagnostic and prognostic role of combined [F-18]FDG and [Ga-68]-DOTA-peptides PET/CT in primary pulmonary carcinoids: a multicentric experience

ObjectivesIn the present retrospective multicentric study, we combined [Ga-68]-DOTA-peptides and [F-18]FDG-PET/CT findings aiming to investigate their capability to differentiate typical (TC) and atypical pulmonary carcinoids (AC) and their prognostic role. MethodsFrom three centers, 61 patients were retrospectively included. Based on a dual tracer combination we classified PET scans as score 1, [F-18]FDG- and [Ga-68]-DOTA-peptides negative; score 2, [68Ga]-DOTA-peptides positive and [F-18]FDG-negative; score 3, [Ga-68]-DOTA-peptides negative and [F-18]FDG-positive; score 4, both tracers positive. Moreover, for each patient, the ratios of SUVmax on [Ga-68]-DOTA-PET to that on [F-18]FDG-PET were calculated (SUVr). ResultsThirty-five patients had a final diagnosis of TC. Twenty-two TC (57%) had positive [Ga-68]-DOTA-peptides PET; instead, 21/26 (81%) AC had positive [F-18]FDG-PET/CT. On dual-tracer analysis, scores 1, 2, 3 and 4 were 13%, 20%, 43% and 24% for all populations; 17%, 26%, 20% and 37% for TC; 8%, 11%, 73% and 8% for AC. Median SUVr was significantly higher in TC than AC (6.4 vs. 0.4, p = 0.011). The best value of SUVr to predict the final diagnosis was 1.05 (AUC 0.889). Relapse or progression of disease happened in 17 patients (11 affected by AC) and death in 10 cases (7 AC). AC diagnosis, positive [F-18]FDG-PET, negative DOTA-PET and dual tracer score were significantly correlated with PFS (p = 0.013, p = 0.033, p = 0.029 and p = 0.019), while only AC diagnosis with OS (p = 0.022). ConclusionPET/CT findings had also a prognostic role in predicting PFS. Dual-tracer PET behavior may be used to predict the nature of pulmonary carcinoids and select the most appropriate management.