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

PurposeA high SUVmax tumor-to-liver ratio (TLR) of Ga-68-DOTATATE can be used to select patients with neuroendocrine tumors (NETs) for peptide receptor radionuclide therapy (PRRT). In addition, an SUVmax TLR & GE; 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 SUVmax of Ga-68-DOTATATE in patients with NET and to identify independent predictors for high SUVmax TLR.Patients and MethodsFor this retrospective study, 192 Ga-68-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 SUVmax values was analyzed by a maximum likelihood mixed model.ResultsPatients with SSA had a significantly higher median SUVmax 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 SUVmax TLR & GE; 8.1 (odds ratio, 2.91; 95% confidence interval, 1.26-6.72; P = 0.012).ConclusionsOur data suggest that higher SSA concentrations do not have a negative effect on Ga-68-DOTATATE uptake in tumor lesions. In addition, we found that only SSA use was associated with SUVmax TLR & GE; 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 Ga-68-DOTATATE PET/CT imaging.

Automated summary

Patients treated with SSA have higher Ga-68-DOTATATE SUVmax TLR values, and the use of SSA is an independent predictor for SUVmax TLR ≥8.1.