Usefulness of F-FDG-PET/CT in the diagnosis and prediction of recurrence of pancreatic neuroendocrine neoplasms.

Background: Although F-FDG-PET/CT is a widely used diagnostic tool for several malignancies, its efficacy in diagnosing pancreatic neuroendocrine tumors is reported to be controversial because of the short-term follow-up.

Methods: We retrospectively compared demographics and pathological features between F-FDG-positive and -negative diseases. Additionally, we evaluated whether the avidity of F-FDG-PET/CT affected earlier recurrence after curative treatment of non-functioning tumors. The median duration of observation was 65.6 months.

Results: Seventy-two patients were enrolled. F-FDG-positive diseases were pathologically advanced and significantly associated with metastatic behavior. In a multivariate analysis, metastatic behavior and WHO tumor grade was independently associated with F-FDG accumulation. Only 25% of functional tumors (4/16) and 8% of insulinomas (1/12) were F-FDG-positive. In a Kaplan-Meier analysis in patients with non-functioning tumors (n = 56), F-FDG-positivity was significantly correlated with poorer recurrence-free survival (RFS) but had no correlation with overall survival. In univariate analysis of factors associated with shorter RFS, male gender, prevalence of nodal metastasis, WHO tumor grade ≥G2, or F-FDG-positive disease were significantly higher in patients with shorter RFS, whereas only F-FDG-positivity was associated with shorter RFS in multivariate analyses.

Conclusions: The avidity of F-FDG-PET/CT was associated with metastatic behavior of pancreatic neuroendocrine tumors and recurrence after treatment of non-functioning tumors.