Abstract
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 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 (WD). 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 has 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.
- Neuroendocrine
- Oncology: Endocrine
- PET/CT
- 18F-FDG PET/CT
- 68Ga-DOTATATE
- clinical impact
- neuroendocrine tumors
- prognosis
- Copyright © 2016 by the Society of Nuclear Medicine and Molecular Imaging, Inc.