The objective of this retrospective study was to determine the role of 18 F-FDG PET/CT in a large cohort of 495 patients with metastatic neuroendocrine neoplasms (NENs) who were treated with peptide receptor radionuclide therapy (PRRT) with a long-term follow-up. Methods: The 495 patients were treated with 177 Lu-and/or 90 Y-DOTATOC/DOTATATE PRRT between 2/2002 and 7/2018. All subjects received both 68 Ga-DOTATOC/TATE/NOC and 18 F-FDG PET/CT prior to treatment and were followed 3-189 months. Kaplan-Meier analysis, log-rank test (Mantel-Cox), and Cox regression analysis were performed for overall survival (OS) and progression-free survival (PFS). Results: 199 patients (40.2%) presented with pancreatic NEN, 49 with CUP (cancer of unknown primary), 139 with midgut NEN, whereas the primary tumor was present in the rectum in 20, in the lung in 38, in the stomach in 8 and other locations in 42 patients. FDG-PET/CT was positive in 382 (77.2%) patients and 113 (22.8%) were FDG-negative before PRRT, while 100% were 68 Ga-DOTATOC/TATE/NOC positive. For all patients, the median PFS and OS, defined from start of PRRT, were 19.6 mo and 58.7 mo, respectively. Positive FDG predicted shorter PFS (18.5 mo vs 24.1 mo; p =0.0015) and OS (53.2 mo vs 83.1 mo; p <0.001) than negative FDG. Amongst the pancreatic NEN, the median OS was 52.8 mo in FDG positive and 114.3 mo in FDG negative subjects (p =0.0006). For all patients with positive 18 F-FDG uptake, and a ratio of the highest SUVmax on 68 Ga-SSTR PET to the most 18 F-FDG-avid tumor lesions >2, the median OS was 53.0 mo, compared to 43.4 mo in those patients with a ratio <2 (p =0.030). For patients with by on November 5, 2020. For personal use only. jnm.snmjournals.org Downloaded from no 18 F-FDG uptake (complete "mismatch" imaging pattern), the median OS was 108.3 mo vs 76.9 mo for SUVmax >15.0 and ≤15.0 on 68 Ga-SSTR PET/CT, respectively. Conclusion: The presence of positive lesions on 18 F-FDG PET is an independent prognostic factor in patients with NEN treated with PRRT. Metabolic imaging with 18 F-FDG PET/CT compliments the molecular imaging aspect of 68 Ga-SSTR PET/CT for the prognosis of survival after PRRT. High SSTR expression combined with negative 18 F-FDG PET/CT imaging is associated with the most favorable long-term prognosis.
