Background:There is limited data on somatostatin receptor (SSTR) expression of metastatic gastroenteropancreatic neuroendocrine tumors (GEP-NETs) using modern imaging techniques and stratifying by primary site and tumor grade (G). Understanding patterns of SSTR expression and tumor heterogeneity is essential when determining the relevance of cold and radiolabeled somatostatin analog treatments.Methods:A single-institutional retrospective analysis of metastatic well-differentiated G1-3 GEP-NET patients who underwent Gallium-68 ([68Ga])-DOTATATE or Copper-64 ([64Cu])-DOTATATE positron emission tomography (PET) imaging from September 2016 to June 2024 was performed.Results:A total of 1192 patients were considered eligible for this study. Among them, 26 (2.2%) were completely negative on SSTR PET/computed tomography (CT), and 27 (2.3%) had weak uptake (less or equal to the normal liver). Up to 40 (3.4%) had heterogeneous SSTR expression on PET/CT: 26 (2.2%) displayed the coexistence of strongly avid lesions with the absence or near absence of SSTR uptake in measurable tumors (heterogeneous strong), while 14 (1.2%) had a combination of absent and weakly expressing SSTR tumors (heterogeneous low). An additional nine cases with prior homogeneous expression (0.8%) developed new SSTR-negative tumors along with disease progression, potentially indicating dedifferentiation. The absent or heterogeneous SSTR expression rates were greater in NET G3 than G1/G2 and in tumors originating outside the small bowel (midgut). Most NETs with absent or heterogeneous SSTR expression were fluorodeoxyglucose-F-18 ([18F]FDG)-avid.Conclusions:The large majority of metastatic GEP-NETs demonstrate strong and relatively uniform SSTR expression, but approximately 8% are SSTR-negative, weak or heterogeneous on PET/CT. Higher than average rates of absent/heterogeneous/weak SSTR expression occur in G3 NETs and lower rates among small intestine primaries.
背景：关于转移性胃肠胰神经内分泌肿瘤（GEP-NETs）生长抑素受体（SSTR）表达的现代影像学数据有限，且缺乏按原发部位和肿瘤分级（G）分层的研究。在评估非标记及放射性标记生长抑素类似物治疗的相关性时，理解SSTR表达模式及肿瘤异质性至关重要。 方法：本研究对2016年9月至2024年6月期间接受镓-68（[68Ga]）-DOTATATE或铜-64（[64Cu]）-DOTATATE正电子发射断层扫描（PET）成像的转移性高分化G1-3级GEP-NET患者进行了单机构回顾性分析。 结果：共有1192例患者符合本研究纳入标准。其中，26例（2.2%）在SSTR PET/计算机断层扫描（CT）上呈完全阴性，27例（2.3%）摄取微弱（低于或等于正常肝脏）。多达40例（3.4%）在PET/CT上表现出异质性SSTR表达：26例（2.2%）在可测量肿瘤中同时存在强摄取病灶与无或近乎无SSTR摄取的病灶（异质性强摄取），而14例（1.2%）则同时存在无摄取和弱摄取SSTR的肿瘤（异质性低摄取）。另有9例（0.8%）既往表达均匀的患者在疾病进展过程中出现新的SSTR阴性肿瘤，可能提示去分化。SSTR无表达或异质性表达的比例在G3级NET中高于G1/G2级，且在非小肠（中肠）起源的肿瘤中更高。大多数SSTR无表达或异质性表达的NET对氟脱氧葡萄糖F-18（[18F]FDG）呈高摄取。 结论：绝大多数转移性GEP-NETs表现出强且相对均匀的SSTR表达，但约8%在PET/CT上呈SSTR阴性、弱摄取或异质性表达。SSTR无表达/异质性表达/弱表达的比例在G3级NET中高于平均水平，而在小肠原发肿瘤中比例较低。
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