Patients with neuroendocrine tumors (NETs) are often treated with somatostatin analogs (SSAs) for control of symptoms and tumor growth. Such therapy could theoretically lead to misinterpretation of somatostatin receptor imaging with ⁶⁸Ga-DOTATATE PET/CT by interfering with tracer–receptor binding. Guidelines recommend an interval of 3–4 wk between the last dose and imaging. The aim of this study was to evaluate if long-acting (LA) SSA treatment changes the uptake of ⁶⁸Ga-DOTATATE in patients with NETs. Methods: From 2013 to 2016, 296 patients with, or under evaluation for, NETs were included in this prospective observational study. The effect of LA SSA on tracer uptake was evaluated in 2 main patient populations: those undergoing ⁶⁸Ga-DOTATATE PET/CT before starting LA SSA treatment and at least once afterward, and those receiving ongoing LA SSA therapy, in whom the effect of the interval between the last dose of LA SSA and the PET/CT exam was analyzed. A third, explorative, analysis was performed to evaluate if clinical disease progression, regression, or stable tumor status changed the uptake of ⁶⁸Ga-DOTATATE. In the 3 analyses, measurements of SUV_max in normal liver and tumor lesions were compared. Results: The median SUV_max in normal liver was significantly higher before treatment (8.6; interquartile range, 7.4–10.2) than after treatment initiation (6.0; 4.7–8.0) (P < 0.001). No significant changes in SUV_max were seen in tumor lesions after treatment initiation. No significant differences in SUV_max were found in normal liver or tumor lesions dependent on the interval between last dose of LA SSA and PET/CT. Conclusion: Treatment with LA SSA does not change SUV_max in tumor lesions, whereas SUV_max in normal liver is significantly lower after treatment. The findings have implications for interpretation of ⁶⁸Ga-DOTATATE PET/CT for response assessment after SSA therapy and for guidelines on discontinuation of treatment before PET/CT.

患有神经内分泌肿瘤（NETs）的患者经常用生长抑素类似物（SSA）治疗，以控制症状和肿瘤生长。从理论上讲，这种治疗可能会通过干扰示踪剂与受体的结合，导致用⁶⁸ Ga-DOTATATE PET / CT误解生长抑素受体的影像。指南建议末次剂量和影像检查之间的间隔为3-4 wk。这项研究的目的是评估长效（LA）SSA治疗是否会改变NETs患者对⁶⁸ Ga-DOTATATE的摄取。方法：从2013年到2016年，该前瞻性观察研究纳入了296例接受NETs或接受NETs评估的患者。在2个主要的患者人群中评估了LA SSA对示踪剂摄取的影响：^68岁的患者Ga-DOTATATE PET / CT在开始进行LA SSA治疗之前和之后至少一次，以及接受正在进行的LA SSA治疗的患者，分析了最后一次LA SSA剂量与PET / CT检查之间的间隔的影响。进行了第三次探索性分析，以评估临床疾病的进展，消退或稳定的肿瘤状态是否改变了⁶⁸ Ga-DOTATATE的摄取。在这3项分析中，比较了正常肝脏和肿瘤病变中SUV _max的测量值。结果：治疗前正常肝脏中的_最大SUV_最大值（8.6；四分位间距为7.4–10.2）明显高于治疗开始后（6.0； 4.7–8.0）（P <0.001）。SUV _max没有明显变化开始治疗后在肿瘤病变中可见到。根据LA SSA和PET / CT的最后剂量之间的间隔，在正常肝脏或肿瘤病变中未发现SUV _max的显着差异。结论：治疗LA SSA不会改变SUV_最大的肿瘤病灶，而SUV_最大值在正常肝是治疗后显著降低。该发现对在SAA治疗后对⁶⁸ Ga-DOTATATE PET / CT的解释作出了评估，以解释在PET / CT之前中止治疗的指南。