The Combined Interpretation of 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT in Metastatic Gastroenteropancreatic Neuroendocrine Tumors
Aimee R. Hayes, Luke Furtado O’Mahony, Ann‐Marie Quigley, Gopinath Gnanasegaran, Martyn Caplin, Shaunak Navalkissoor, Christos Toumpanakis
Abstract
Purpose Gastroenteropancreatic neuroendocrine neoplasms (GEP NEN) are widely heterogeneous in their biological behavior, and predicting prognosis and optimal treatment strategies can be challenging. 68 Ga-DOTATATE PET/CT is a sensitive imaging modality for well-differentiated NEN and indicates a favorable prognosis, whereas 18 F-FDG PET/CT avidity indicates disease that is potentially more aggressive. There has been emerging interest in the combined interpretation of 68 Ga-DOTATATE and 18 F-FDG PET and its prognostic significance. We aimed to assess the prognostic utility of a classification system that incorporates the complex findings of 68 Ga-DOTATATE and 18 F-FDG PET interpreted side-by-side in patients with metastatic GEP NEN. Methods We defined 3 68 Ga-DOTATATE/ 18 F-FDG “dual-tracer PET” groups: D1 ( 68 Ga-DOTATATE positive/ 18 F-FDG negative), D2 ( 68 Ga-DOTATATE positive/ 18 F-FDG positive), and D3 ( 68 Ga-DOTATATE negative/ 18 F-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 68 Ga-DOTATATE and 18 F-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 68 Ga-DOTATATE and 18 F-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.