The Influence of Long-Acting Somatostatin Analogs on (68)Ga-DOTATATE Uptake in Patients With Neuroendocrine Tumors

A high SUV(max) tumor-to-liver ratio (TLR) of (68)Ga-DOTATATE can be used to select patients with neuroendocrine tumors (NETs) for peptide receptor radionuclide therapy (PRRT). In addition, an SUV(max) TLR ≥ 8.1 is associated with increased progression-free survival in NET patients treated with somatostatin analogs (SSAs). To avoid a theoretical interaction, several guidelines recommend performing PET/CT just before the monthly administration of long-acting SSAs. We aimed to investigate the effect of SSA on the SUV(max) of (68)Ga-DOTATATE in patients with NET and to identify independent predictors for high SUV(max) TLR. PATIENTS AND METHODS: For this retrospective study, 192 (68)Ga-DOTATATE PET/CT scans of 165 patients without (n = 115) and with (n = 77) SSA (octreotide or lanreotide) in the 3 months before PET/CT were collected and reviewed. The effect of SSA on SUV(max) values was analyzed by a maximum likelihood mixed model. RESULTS: Patients with SSA had a significantly higher median SUV(max) TLR than patients without SSA (4.7 [IQR], 3.1–7.7) versus 3.2 [IQR, 2.0–5.4]; P < 0.001). Multivariable logistic regression analysis showed that SSA use was an independent predictor for SUV(max) TLR ≥ 8.1 (odds ratio, 2.91; 95% confidence interval, 1.26–6.72; P = 0.012). CONCLUSIONS: Our data suggest that higher SSA concentrations do not have a negative effect on (68)Ga-DOTATATE uptake in tumor lesions. In addition, we found that only SSA use was associated with SUV(max) TLR ≥ 8.1. Our results are consistent with previously conducted studies and in line with the recently published guideline that suggests that the relatively recent use of SSA does not necessitate any delay in (68)Ga-DOTATATE PET/CT imaging.