Abstract
PurposeSince the role of [18F]FDG PET/CT in low-grade gastroenteropancreatic (GEP) neuroendocrine neoplasia (NET) is not well established, this study was aimed to evaluate the role of [18F]FDG PET/CT in grade 1 (G1) GEP-NETs.MethodsThis is a retrospective study including patients with G1 GEP-NETs who underwent [18F]FDG PET/CT.Results55 patients were evaluated, including 24 (43.6%) with pancreatic NETs and 31 (56.4%) with gastrointestinal NETs. At the time of diagnosis, 28 (51%) patients had metastatic disease, and 50 (91%) patients were positive by 68-Ga sstr PET/CT. Overall, 27 patients (49%) had positive findings on [18F]FDG PET/CT. Following [18F]FDG PET/CT, therapeutic management was modified in 29 (52.7%) patients. Progression-free survival was longer in patients with negative [18F]FDG PET/CT compared with positive [18F]FDG PET/CT (median PFS was not reached and 24 months, respectively, p = 0.04). This significance was particularly evident in the pancreatic group (p = 0.008).ConclusionsDespite having low proliferative activity, approximately half of GEP-NETs G1 showed positive [18F]FDG PET/CT, with a corresponding negative impact on patients’ clinical outcomes. These data are in favor of a more “open” attitude toward the potential use of [18F]FDG PET/CT in the diagnostic work-up of G1 GEP-NETs, which may be used in selected cases to detect those at higher risk for an unfavorable disease course.
Highlights
Gastroenteropancreatic (GEP) neuroendocrine neoplasia (NEN) is a rare and heterogeneous disease arising from the diffuse neuroendocrine system of the gastrointestinal tract and pancreas [1]
25 (31.2%) patients were excluded because minimal follow-up data were not available (n = 10), there was a grading modification after repeating histological assessment in patients referred to the Centers from other hospitals (n = 10), and a Ki67 value was missing and it was not possible to repeat histological assessment due to tissue unavailability (n = 5)
Similar to what is already known in more aggressive NENs, the present study shows that positive [18F]FDG PET/CT is associated with a poor clinical outcome in terms of progression-free survival (PFS not reached in [18F]FDG PET/CT-negative patients and 24 months in FDG-positive patients, p = 0.04)
Summary
Gastroenteropancreatic (GEP) neuroendocrine neoplasia (NEN) is a rare and heterogeneous disease arising from the diffuse neuroendocrine system of the gastrointestinal tract and pancreas [1]. Its prognosis is affected by several factors, including primary tumor site, staging, and grading The latter is more important for risk stratification and therapeutic choice [2, 3]. Even if grade 1 (G1) NETs are considered indolent tumors with a very low progressive growth pattern, in some cases, especially in patients with metastases, the disease course could be rapidly progressive with a worse response to medical treatment. This reflects an intrinsic hallmark of NENs, tumor heterogeneity, which may translate into nonhomogeneous
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