Synthetic somatostatin analogs have been posed as a potential source of error in somatostatin receptor imaging through interference with tumor detection; however, experimental models and clinical studies have shown a complex mechanism of the effect of octreotide on tumors. The aim of this study was to assess whether ⁶⁸Ga-DOTATATE uptake before treatment with long-acting somatostatin analogs differs from that after treatment. Methods: Thirty patients (15 men; age [mean ± SD], 64.6 ± 13.4 y) who had intermediately differentiated to well-differentiated neuroendocrine tumors and who underwent ⁶⁸Ga-DOTATATE PET/CT scanning before and after receiving long-acting repeatable octreotide (Sandostatin LAR) were included in the study. The SUV_max and SUV_mean of healthy target organs, residual primary tumor, and up to 5 lesions with the highest SUV_max in each organ were compared before and after octreotide treatment. Results: The mean time interval between the 2 ⁶⁸Ga-DOTATATE studies was 9.6 ± 7.2 mo, and the mean time gap between the last Sandostatin LAR injection and the second ⁶⁸Ga-DOTATATE study was 25.1 ± 14.8 d. The pretreatment mean SUV_max and SUV_mean were both significantly higher in the thyroid, liver, and spleen (P < 0.05) than the values measured after the administration of Sandostatin LAR. No significant differences were found among the uptake indices for residual primary tumor or any metastatic lesions in the liver, bone, lung, or lymph nodes before and after Sandostatin LAR administration (P > 0.05). Conclusion: Long-acting octreotide treatment diminished ⁶⁸Ga-DOTATATE uptake in the liver, spleen, and thyroid but did not compromise tracer uptake in residual primary tumor and metastatic lesions. These findings have a direct impact on the interpretation of ⁶⁸Ga-DOTATATE PET/CT scans.

合成的生长抑素类似物通过干扰肿瘤检测已被认为是生长抑素受体成像中潜在的错误来源。然而，实验模型和临床研究表明，奥曲肽对肿瘤的作用机制复杂。这项研究的目的是评估长效生长抑素类似物治疗前⁶⁸ Ga-DOTATATE的摄入量是否与治疗后有所不同。方法： 30例患者（15名男性，年龄[平均值±标准偏差]，64.6±13.4岁），中分化为高分化神经内分泌肿瘤，并在接受长效可重复奥曲肽治疗前后接受了⁶⁸ Ga-DOTATATE PET / CT扫描（Sandostatin LAR）纳入研究。SUV_最大比较奥曲肽治疗前后健康靶器官，残留原发肿瘤以及每个器官中_最多5个具有SUV _max最高的病变的SUV_平均值。结果： 2 ⁶⁸ Ga-DOTATATE研究之间的平均时间间隔为9.6±7.2 mo，最后一次Sandostatin LAR注射与第二次⁶⁸ Ga-DOTATATE研究之间的平均时间间隔为25.1±14.8 d。甲状腺，肝脏和脾脏的预处理均值SUV _max和SUV_均值均显着较高（P<0.05）高于Sandostatin LAR给药后测得的值。在服用Sandostatin LAR前后，残余原发肿瘤或肝脏，骨骼，肺或淋巴结中任何转移性病变的摄取指数之间均无显着差异（P > 0.05）。结论：长效奥曲肽治疗减少了肝，脾和甲状腺中⁶⁸ Ga-DOTATATE的摄取，但并未损害残留的原发肿瘤和转移性病变中示踪剂的摄取。这些发现直接影响了⁶⁸ Ga-DOTATATE PET / CT扫描的解释。