Functional imaging in neuroendocrine tumors: assessment of molecular heterogeneity using [68Ga]Ga-DOTA-TOC and [18F]FDG PET/CT

Objective

The aim of the study was evaluate the diagnostic performance of [⁶⁸Ga]Ga-DOTA-TOC and [¹⁸F]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 [⁶⁸Ga]Ga-DOTA-TOC and [¹⁸F]FDG PET/TC. The pooled sensitivity of both scans was compared, as well as [⁶⁸Ga]Ga-DOTA-TOC and [¹⁸F]FDG for each tumor grade (grade 1/G1, grade 2/G2 and grade 3/G3). Also, the sensitivity of [⁶⁸Ga]Ga-DOTA-TOC and [¹⁸F]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 [¹⁸F]FDG (44%) separately, with statistically significant differences. The sensitivity of [⁶⁸Ga]Ga-DOTA-TOC was higher than [¹⁸F]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 [⁶⁸Ga]Ga-DOTA-TOC and [¹⁸F]FDG PET/CT correlated significantly with the Ki-67 proliferative index. In G2 patients the number of lesions detected with [⁶⁸Ga]Ga-DOTA-TOC was higher than [¹⁸F]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).