Hypoattenuation Pattern on Contrast-Enhanced Computed Tomography Predicts Poor Prognosis in Patients with Pancreatic Neuroendocrine Tumors

Background/Objectives: Several reports have shown that the hypoattenuation pattern of contrast-enhanced computed tomography (CECT) in pancreatic neuroendocrine tumors (PanNETs) is associated with poor overall survival (OS). However, these studies also included neuroendocrine carcinoma. Therefore, this study retrospectively investigated the relationship between attenuation patterns and OS, specifically in PanNETs. Methods: Between July 2005 and August 2022, 80 consecutive patients (median age, 64 years; 39 males and 41 females) with pathologically confirmed PanNETs were enrolled. Pretreatment factors associated with PanNET prognosis were evaluated. Results: The median tumor diameter was 18 mm (range, 6–150 mm). The PanNET grades were G1 in 45 patients (56%), G2 in 31 (39%), and G3 in 4 (5%). Hyperattenuation and hypoattenuation patterns were observed in 64 (80%) and 16 (20%) patients, respectively. Surgery was performed on 63 patients (79%), and 18 (23%) had distant metastases. Multivariate analysis identified the hypoattenuation pattern on pretreatment CECT as a factor significantly associated with OS in all participants (p < 0.001; hazard ratio [HR], 9.45) and in patients with PanNET G2 (p = 0.007; HR, 9.13). Median OS was longer in the hyperattenuation group than in the hypoattenuation group among all participants (hyperattenuation, not reached; hypoattenuation, 40.1 months; p < 0.001) and among patients with PanNET G2 (hyperattenuation, not reached; hypoattenuation, 36.3 months; p = 0.001). Conclusions: PanNETs with a hypoattenuation pattern on CECT had a worse prognosis than those with hyperattenuation, even among tumors of the same pathological grade (G2).