The clinical benefits of [18F]AlF-NOTA-octreotide PET/CT in staging and restaging patients with gastroenteropancreatic neuroendocrine neoplasms: comparison of [18F]FDG PET/CT

Accurate clinical TNM staging is crucial for managing GEP-NENs according to the latest NCCN guidelines. [68Ga] labeled somatostatin receptor (SSTR) PET/CT outperforms [18F]FDG PET/CT in evaluating well and moderately differentiated NENs. However, few studies have investigated the performance of [18F] labeled SSTRs in the exploration of GEP-NENs. This retrospective study compared the performance of [18F]AlF-NOTA-octreotide ([18F]OC) with [18F]FDG PET/CT for precise staging and restaging GEP-NENs. Participants with clinically suspected or confirmed NENs were enrolled and underwent paired [18F]OC and [18F]FDG PET/CT between. Lesion findings and PET metabolic parameters, such as the maximum standardized uptake value (SUVmax) and tumor-to-background ratio (TBR), were compared between the two types of radiotracers. The results of histology or imaging follow-up served as the reference standard for the final diagnosis. Thirty-seven patients and 209 suspicious lesions were included in the statistical analysis. In patients for initial staging (n = 19), [18F]OC PET/CT led to upstaging of the clinical T stage in 13 (66.7%) patients and TNM stage in 10 (52.6%) patients compared with [18F]FDG PET/CT. In posttreatment patients for restaging (n = 18), [18F]OC PET/CT demonstrated superior performance in 9 (50%) patients and inferior performance in 3 (16.7%) patients compared with [18F]FDG PET/CT. For the 176 confirmed NEN lesions, the SUVmax and TBR of [18F]OC were greater than those of [18F]FDG (median SUVmax, 11.3 vs. 2.1; P < 0.001; median TBR, 8.0 vs. 1.6; P < 0.001, respectively). For lesions < 0.5 cm, 0.5 ~ 1.0 cm and 1.0 ~ 2.0 cm in size, [18F]OC PET/CT had a significantly higher sensitivity than [18F]FDG PET/CT did (P = 0.041, < 0.001, 0.028, respectively), whereas for lesions between 2.0 ~ 4.0 cm and > 4.0 cm in size, the differences were not significant (P = 0.103 and 0.539). [18F]OC PET/CT outperformed [18F]FDG PET/CT in detecting small well-differentiated GEP-NEN lesions and metastases less than 2.0 cm in size, even tiny lesions (≤ 0.5 cm), which helps improve GEP-NEN staging and restaging. Not applicable.