Comparison of the Impact of ⁶⁸Ga-DOTATATE and ¹⁸F-FDG PET/CT on Clinical Management in Patients with Neuroendocrine Tumors

Abstract

This study aimed to assess the clinical impact of 68 Ga-DOTATATE and 18 F-FDG with respect to the management plan and to evaluate the prognostic value of both tracers. Methods: A total of 104 patients (55 male and 49 female; median age, 58 y; range, 20-90 y) with histologically proven neuroendocrine tumors (NETs) underwent both 68 Ga-DOTATATE and 18 F-FDG PET/CT. . Results: The 68 Ga-DOTATATE and 18 F-FDG PET/CT findings were discordant in 65 patients (62.5%) and concordant in 39 patients (37.5%). The results changed the therapeutic plan in 84 patients (80.8%). In 22 patients (21.1%), decision making was based on the 18 F-FDG findings; in 32 (30.8%), on the findings with both radiotracers; and in 50 (48.1%), on the 68 Ga-DOTATATE findings. The most frequent management decision based on 18 F-FDG was initiation of chemotherapy (10 patients, 47.6%). The most common treatment decision due to 68 Ga-DOTATATE was initiation of peptide receptor radionuclide therapy (14 patients, 27.4%). In 11 (39.2%) of 28 patients with poorly differentiated NETs, the management decision was based on only the 18 F-FDG results. For 68 Ga-DOTATATE, SUV max was higher for G1 tumors and lower for G3 tumors (P 5 0.012). However, no significant differences in 18 F-FDGderived SUVs were observed between different grades (P 5 0.38). The Mann-Whitney test showed significant differences in 68 Ga-DOTATATE SUV max between tumors with a Ki-67 of less than 5% and tumors with a Ki-67 of more than 5% (P 5 0.004), without significance differences in 18 F-FDG SUV max . Log-rank analysis showed statistically significant differences in survival for patients with bone metastasis versus soft-tissue or no metastasis for both 18 F-FDG (P 5 0.037) and 68 Ga-DOTATATE (P 5 0.047). Overall survival declined rapidly with increasing grade (P 5 0.001), at an estimated 91 mo for G1, 59 mo for G2, and 48 mo for G3. Conclusion: 18 F-FDG PET/CT had no clinical impact on G1 NETs and a moderate impact on G2 NETs. However, in poorly differentiated NETs, 18 F-FDG PET/CT plays a significant clinical role in combination with 68 Ga-DOTATATE. 68 Ga DOTATATE SUV max relates to grade and Ki-67 and can be used prognostically.

Most of the Intended Management Changes After 68Ga-DOTATATE PET/CT Are Implemented

“…However, one concern about the National Oncology PET Registry is that intended management changes may not have been implemented (5,6). In the current study, 68 Ga-DOTATATE PET/CT resulted in intended management changes in 48 of 96 patients (50%), which is comparable to results from prior retrospective studies (2,3,(7)(8)(9)(10)(11). However, no prospective study has elucidated prospectively the rate of implemented management changes.…”

Molecular Imaging of Gastroenteropancreatic Neuroendocrine Tumors: Current Status and Future Directions

“…18 F-FDG PET/CT is considered the preferred radiotracer for G3 tumors, as well as for some high-grade G2 tumors. The role of 18 F-FDG PET/CT in G1 tumors or in low-grade G2 tumors is still debated (51). A Ki-67 of at least 10% is often considered the cutoff for proposing the use of 18 F-FDG PET/CT for welldifferentiated G2 NETs (52).…”

Current Concepts in 68Ga-DOTATATE Imaging of Neuroendocrine Neoplasms: Interpretation, Biodistribution, Dosimetry, and Molecular Strategies

“…Vice versa, 68 Ga-SSA PET/CT in cases presenting higher Ki-67 values (.50%), even if positive, will likely not affect management. The added value of 18 F-FDG in welldifferentiated NENs (G1 and G2) is still under debate, and no international consensus has been reached (49)(50)(51)(52)(53).…”

“…Recently, it was in fact shown that 18 F-FDG PET/CT should be used only in selected cases, with a Ki-67 of less than 12% (53), as in such cases the clinical management uniquely relies on 68 Ga-DOTATATE.…”