Dual-Tracer (68Ga-DOTATOC and 18F-FDG-)-PET/CT Scan and G1-G2 Nonfunctioning Pancreatic Neuroendocrine Tumors: A Single-Center Retrospective Evaluation of 124 Nonmetastatic Resected Cases

Introduction: The combined use of (68)gallium (Ga-68)-DOTA-peptides and (18)fluorine-fluoro-2-deoxyglucose (F-18-FDG) positron emission tomography/computed tomography (PET/CT) scans in the workup of pancreatic neuroendocrine tumors (PanNETs) is controversial. This study aimed at assessing both tracers' capability to identify tumors and to assess its association with pathological predictors of recurrence. Methods: Prospectively collected, preoperative, dual-tracer PET/CT scan data of G1-G2, nonmetastatic, PanNETs that underwent surgery between January 2013 and October 2019 were retrospectively analyzed. Results: The final cohort consisted of 124 cases. There was an approximately equal distribution of males and females (50.8%/49.2%) and G1 and G2 tumors (49.2%/50.8%). The disease was detected in 122 (98.4%) and 64 (51.6%) cases by Ga-68-DOTATOC and by F-18-FDG PET/CT scans, respectively, with a combined sensitivity of 99.2%. F-18-FDG-positive examinations found G2 tumors more often than G1 (59.4 vs. 40.6%; p = 0.036), and F-18-FDG-positive PanNETs were larger than negative ones (median tumor size 32 mm, interquartile range [IQR] 21 vs. 26 mm, IQR 20; p = 0.019). The median Ki67 for F-18-FDG-positive and -negative examinations was 3 (IQR 4) and 2 (IQR 4), respectively (p = 0.029). At least 1 pathological predictor of recurrence was present in 74.6% of F-18-FDG-positive cases (vs. 56.7%; p = 0.039), whereas this was not found when dichotomizing the PanNETs by their dimensions (<=/>20 mm). None of the 2 tracers predicted nodal metastasis. The receiver operating characteristic curve analysis showed that F-18-FDG uptake higher than 4.2 had a sensitivity of 49.2% and specificity of 73.3% for differentiating G1 from G2 (AUC = 0.624, p = 0.009). Conclusion: The complementary adoption of Ga-68-DOTATOC and F-18-FDG tracers may be valuable in the diagnostic workup of PanNETs despite not being a game-changer for the management of PanNETs <= 20 mm.

Automated summary

This study retrospectively analyzed dual-tracer PET/CT scan data of G1-G2 nonmetastatic PanNETs, finding a combined sensitivity of 99.2% for Ga-68-DOTATOC and F-18-FDG PET/CT scans. F-18-FDG-positive examinations more often detected G2 tumors and larger PanNETs, with a median Ki67 difference between positive and negative examinations.