Abstract
Grade 3 (G3) neuroendocrine tumors (NETs) are a novel category among digestive neuroendocrine neoplasms, characterized by Ki-67 >20% and a well-differentiated morphology, presenting high intra-tumor heterogeneity. We aimed to explore the role of dual-tracer PET imaging (68Gallium (Ga)-DOTATOC and 18Fluorodeoxyglucose (FDG)) as overall survival (OS) predictor in NET G3 patients. We performed a retrospective analysis in NET G3 patients treated at our institution between 2003 and 2021. Accordingly, 30 NET G3 patients were analyzed. 68Ga-DOTA-TOC and 18F-FDG uptake were assessed by tumor/non-tumor (T-nonT) ratio. We reported a slightly better OS for patients with ≥75% concordance between 68Ga-DOTA-TOC and 18F-FDG PET/CT (p = 0.42). Among patients with discordant functional imaging, we reported a better 5-y OS rate for patients with a prevalent 68Ga-DOTATOC vs. 18F-FDG PET/CT (p = 0.016). In positive 18F-FDG PET/CT cases, we reported a better OS for <4 vs. ≥4 T/non-T ratio (p = 0.021). Among upfront-NET G3 patients with concordant exams, 5-y OS rate was 83.3% (95% CI: 27.3–97.5). Among patients with discordant exams, 5-y OS rate was 81.3% (52.5–93.5), 100% for those with prevalent receptor expression, and 50% (11.1–80.4) for those with prevalent 18F-FDG uptake. Our findings suggest that dual-tracer PET/CT can be considered as a predictor of patient outcome, able to stratify NET G3 patients with poorer prognosis.
Highlights
Gastro-entero-pancreatic (GEP) neuroendocrine tumors (NETs) represent a category of rare and well-differentiated neoplasms, well-known for a more indolent biologic behavior compared with their non-neuroendocrine counterparts [1,2]
We aimed to explore the role of dual-tracer PET imaging (68Gallium (Ga)-DOTATOC and 18Fluorodeoxyglucose (FDG)) as overall survival (OS) predictor in NET Grade 3 (G3) patients
Our findings suggest that dual-tracer PET/CT can be considered as a predictor of patient outcome, able to stratify NET G3 patients with poorer prognosis
Summary
Gastro-entero-pancreatic (GEP) neuroendocrine tumors (NETs) represent a category of rare and well-differentiated neoplasms, well-known for a more indolent biologic behavior compared with their non-neuroendocrine counterparts [1,2]. The World Health Organization (WHO) classification of GEP NENs introduced the NET G3 category, a novel entity, morphologically and prognostically separated from poorly-differentiated NECs [3,4]. The diagnosis of NET G3 is based on two pathologic features: a high proliferation index (Ki-67 >20%), and a well-differentiated morphology. NETs G3 might virtually present a proliferation index from 20% to 100% as well as maintaining a well-differentiated morphology. Different clinical, pathological, and radiological (including positron emission tomography, PET) features within the category suggested a greater heterogeneity than presumed, and the need to develop a multiparametric system of the NET G3 classification has grown. This study was designed to explore the role of dual-tracer PET imaging (both using 18F-FDG and 68Ga-DOTA-TOC) in NET G3 patients and to assess possible associations with clinical outcomes
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