The Combined Interpretation of Ga-68-DOTATATE PET/CT and F-18-FDG PET/CT in Metastatic Gastroenteropancreatic Neuroendocrine Tumors A Classification System With Prognostic Impact

Purpose Gastroenteropancreatic neuroendocrine neoplasms (GEP NEN) are widely heterogeneous in their biological behavior, and predicting prognosis and optimal treatment strategies can be challenging. Ga-68-DOTATATE PET/CT is a sensitive imaging modality for well-differentiated NEN and indicates a favorable prognosis, whereas F-18-FDG PET/CT avidity indicates disease that is potentially more aggressive. There has been emerging interest in the combined interpretation of Ga-68-DOTATATE and F-18-FDG PET and its prognostic significance. We aimed to assess the prognostic utility of a classification system that incorporates the complex findings of Ga-68-DOTATATE and F-18-FDG PET interpreted side-by-side in patients with metastatic GEP NEN. Methods We defined 3 Ga-68-DOTATATE/F-18-FDG "dual-tracer PET" groups: D1 (Ga-68-DOTATATE positive/F-18-FDG negative), D2 (Ga-68-DOTATATE positive/F-18-FDG positive), and D3 (Ga-68-DOTATATE negative/F-18-FDG positive). We retrospectively assessed the association between the dual-tracer PET classification and progression-free and overall survival (OS) using Kaplan-Meier analysis. Univariate and multivariate analyses were performed using the Cox proportional hazards model. Results Eighty-seven patients with metastatic GEP NEN and contemporaneous Ga-68-DOTATATE and F-18-FDG PET were included. The dual-tracer PET classification was an independent predictor of OS (multivariate P = 0.016) and also predicted progression-free survival (univariate P = 0.030). Other independent predictors of OS included chromogranin A and World Health Organization (WHO) grade. WHO grade was not associated with OS from the time of dual-tracer PET but was an independent predictor of OS from the date of histological diagnosis (multivariate P = 0.003). Conclusion Our study demonstrates that a classification system combining the complex findings of Ga-68-DOTATATE and F-18-FDG PET is correlated with prognosis. Further research is needed to prospectively validate these findings and to explore whether dual-tracer PET scores may also be able to predict response to treatment.