This study aimed to assess the clinical impact of 68Ga-DOTATATE and 18F-fluorodeoxyglucose
with respect to the management plan and to evaluate the prognostic value of both tracers.
Methods: A total of 104 patients (55 males, 49 females; median age 58 years, range 20–90) with
histopathologically proven neuroendocrine tumors (NETs) underwent both 68Ga-DOTATATE
and 18F-FDG PET/CT. Twenty-eight patients (26.9%) had poorly differentiated (PD) and 76
(73.1%), well-differentiated tumors. PET/CT results and SUVs were compared with prognostic
factors such as pathologic grading (G1, G2, G3), chromogranin A, and proliferation index
(Ki67).
Results: 68Ga-DOTATATE and 18F-FDG PET/CT findings were discordant in 65 (62.5%) and
concordant in 39 (37.5%) pts. PET/CT results changed the therapeutic plan in 84 (80.8%) pts. In
22 (21.1%) pts decision making was based on 18F-FDG findings, in 32 (30.8%) on findings with
both radiotracers, and in 50 (48.1%) on 68Ga-DOTATATE findings. The most frequent
management decision based on 18F-FDG was initiation of chemotherapy (10 pts, 47.6%). The
most common treatment decision due to 68Ga-DOTATATE was initiation of peptide receptor
radionuclide therapy (14 pts, 27.4%). In 11/28 (39.2%) pts with PD NETs the management
decision was based only on 18F-FDG results. For 68Ga-DOTATATE, SUVmax was higher for G1
and lower for G3 tumors (p=0.012). However, no significant differences in 18F-FDG-derived
SUVs were observed between different tumor grades (p=0.38). Mann-Whitney test showed
significant differences in 68Ga-DOTATATE SUVmax between tumors with Ki<5% and tumors
with Ki>5% (p=0.004), without significance differences in 18F-FDG SUVmax. Log-rank analysis
showed statistically significant differences in survival for patients with bone vs soft tissue or no
metastasis for both 18F-FDG (p=0.037) and 68Ga-DOTATATE (p=0.047). Overall survival was
found to decline rapidly with increasing histological grade (p=0.001), with estimated survival of
91 months for G1, 59 months for G2, and 48 months for G3.
Conclusion: 18F-FDG PET/CT had no clinical impact in G1 NETs and moderate impact in G2
NETs. However in PD NETs, 18F-FDG PET/CT plays a significant clinical role in combination
with 68Ga-DOTATATE. 68Ga DOTATATE SUVmax values relate to tumor grade and Ki67 index
and can be used prognostically
