1185P [18F]FDG-PET/CT and long-term response to everolimus in advanced neuroendocrine neoplasia

Abstract

In the last few years, 18F-fluorodeoxyglucose PET/CT (FDG-PET) has emerged as an important tool to define tumor aggressiveness and give relevant prognostic information, with several studies investigating its role in the diagnostic approach and during the follow-up of NENs. However, although a positive correlation between FDG-PET and other well-known predictors of response to anti-tumor therapy as Ki67 has been demonstrated, the ability of this diagnostic tool to predict treatment efficacy is not well established. Furthermore, the possible impact of positive FDG-PET on everolimus efficacy remains unclear. This study aims to identify, in these patients, potential correlation between FDG-PET findings and response to therapy in search of a predictor of long-term efficacy. Retrospective analysis of patients with sporadic, advanced, progressive NEN treated with everolimus, with available data on FDG-PET before commencing therapy. Data is expressed as median (25th – 75th IQR). Risk factor analysis and survival analysis are performed by logistic regression and Cox proportional-hazard regression and Kaplan-Meier curves, as appropriate. Sixty-six patients evaluated (NET G1 19.7%, NET G2 75.7%, NET G3 4.6%), including 45.4% with positive FDG-PET. Overall, disease stabilization and partial response were obtained in 71.2% and 6% of patients, respectively. Long-term response (> 24 months) was observed in 33% of patients. Ki67 was the only predictor for tumor progression (p=0.03). No significant difference in clinical outcome was observed between patients with positive or negative FDG-PET (median PFS was 24 months and 18 months, respectively, p=0.337; disease control rate was 83.3% and 70%, respectively, p=0.245). Everolimus is a valid therapeutic option for advanced, progressive, well-differentiated NENs, even in those patients with positive FDG-PET.