Ga-68-Edotreotide Positron Emission Tomography/Computed Tomography Somatostatin Receptors Tumor Volume Predicts Outcome in Patients With Primary Gastroenteropancreatic Neuroendocrine Tumors

BACKGROUND: We retrospectively aimed to assess the prognostic significance of somatostatin receptor (SSTR) standardized uptake value (SUVmax(sstr)), SSTR representative tumor volume (RTV(sstr)) and total lesion SSTR expression (TL(sstr)) obtained by [(68)Ga]Ga-edotreotide PET/CT ([(68)Ga]Ga-SSTR PET/CT) in patients with primary gastroenteropancreatic neuroendocrine tumors (GEP-NET) before surgery. MATERIAL AND METHODS: We analyzed patients who underwent [(68)Ga]Ga-SSTR PET/CT 3-6 weeks before surgery from February 2020 to April 2022. The mean SUVmax(sstr) value, the RTV(sstr) (cm3; 42% threshold) and the TL(sstr) (g) were registered. Thereafter the patients were followed up 10.3 months (range 3-27). The PET/CT results were compared to the event free survival (EFS). RESULTS: Forty-two patients (61 ± 13 years) have been enrolled. At multivariate analysis only RTV(sstr) values were predictive. The Kaplan-Meier survival analysis for RTV(sstr) showed a significant better EFS in patients presenting lower values as compared to those having greater (P = .003, log-rank test). SUVmax(sstr) was not suitable for predicting EFS, TL(sstr) mildly. CONCLUSION: RTV(sstr) represents a valuable volumetric parameter able to predict the outcome in GEP-NET patients who underwent surgery. The magnitude of the SSTR representative tumor burden holds a predominant value for determining the response to therapy in GEP-NET patients before surgery, rather than the maximal SSTR representation at single voxel.