Functional imaging in neuroendocrine tumors: assessment of molecular heterogeneity using [Ga]Ga-DOTA-TOC and [F]FDG PET/CT.

Objective: The aim of the study was evaluate the diagnostic performance of [Ga]Ga-DOTA-TOC and [F]FDG PET/CT in patients with histologically proven neuroendocrine tumors (NETs), as well as the correlation of the visualized findings with the tumor grade.

Material And Methods: We included 50 patients with NETs who underwent both [Ga]Ga-DOTA-TOC and [F]FDG PET/TC. The pooled sensitivity of both scans was compared, as well as [Ga]Ga-DOTA-TOC and [F]FDG for each tumor grade (grade 1/G1, grade 2/G2 and grade 3/G3). Also, the sensitivity of [Ga]Ga-DOTA-TOC and [F]FDG as a function of the continuous variable Ki-67 was investigated. Finally, the number of lesions detected by both PET radiopharmaceuticals for each tumor grade was compared.

Results: The pooled sensitivity of both PET/CT (96%) was higher than [68Ga]Ga-DOTA-TOC (84%) and [F]FDG (44%) separately, with statistically significant differences. The sensitivity of [Ga]Ga-DOTA-TOC was higher than [F]FDG in both G1 (p = 0.004) and G2 (p < 0.001). In G3 the performance of both scans detected disease in 100% of this subgroup. The sensitivity of [Ga]Ga-DOTA-TOC and [F]FDG PET/CT correlated significantly with the Ki-67 proliferative index. In G2 patients the number of lesions detected with [Ga]Ga-DOTA-TOC was higher than [F]FDG.

Conclusions: The performance of both PET/CT, particularly in G2 and G3, demonstrates the molecular heterogeneity of metastatic NETs and contributes to the selection of a more appropriate treatment, particularly in those high-grade patients who may benefit from radionuclide therapy (PRRT).