Radiolabeled somatostatin (sst) receptor agonists are integral to the diagnosis of gastroenteropancreatic neuroendocrine tumors (NETs), but detection rates, especially of liver metastases, remain limited even with PET/CT. ⁶⁸Ga-OPS202 (⁶⁸Ga-NODAGA-JR11; NODAGA = 1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid and JR11 = Cpa-c(dCys-Aph(Hor)-dAph(Cbm)-Lys-Thr-Cys)-dTyr-NH₂)), a novel radiolabeled sst receptor antagonist with a high affinity for the sst₂ receptor, has the potential to perform better than sst receptor agonists. Here, we present the results of the phase II component of a phase I/II study that evaluated the sensitivity of ⁶⁸Ga-OPS202, compared with the reference compound, ⁶⁸Ga-DOTATOC (an sst receptor agonist), in PET imaging. Methods: Patients received a single 150-MBq intravenous injection of ⁶⁸Ga-DOTATOC (15 μg of peptide) and 2 single 150-MBq intravenous injections of ⁶⁸Ga-OPS202 (15 μg of peptide at visit 1 and 50 μg at visit 2). Whole-body PET/CT acquisitions were performed 1 h after injection on the same calibrated PET/CT scanner. Diagnostic efficacy measures were compared against contrast medium-enhanced CT or MRI as the gold standard. Two independent masked experts read the scans, and both outcomes were combined for analysis. Results: Twelve consecutive patients with low- or intermediate-grade gastroenteropancreatic NETs took part in this prospective study. Image contrast for matched malignant liver lesions was significantly higher for the ⁶⁸Ga-OPS202 scans than for the ⁶⁸Ga-DOTATOC scan: the median of the mean tumor-to-background SUV_max ratios were significantly higher for 15 and 50 μg of ⁶⁸Ga-OPS202 (5.3 and 4.3, with interquartile ranges of 2.9-5.7 and 3.4-6.3 and P values of 0.004 and 0.008) than for ⁶⁸Ga-DOTATOC (1.9, with an interquartile range of 1.4-2.9). The higher tumor-to-background ratio of ⁶⁸Ga-OPS202 resulted not only in a higher detection rate of liver metastases but also in a significantly higher lesion-based overall sensitivity with the antagonist than with ⁶⁸Ga-DOTATOC: 94% and 88% for 50 and 15 μg of ⁶⁸Ga-OPS202, respectively, and 59% for 15 μg of ⁶⁸Ga-DOTATOC (P < 0.001). Positive predictive values for ⁶⁸Ga-OPS202 PET/CT and ⁶⁸Ga-DOTATOC PET/CT were similar (∼98%). There were no significant differences in image contrast, sensitivity, or positive predictive values between the 2 ⁶⁸Ga-OPS202 peptide doses, indicating a high reproducibility. Conclusion: Preliminary diagnostic efficacy data from this phase II study indicate that ⁶⁸Ga-OPS202 has high sensitivity for the detection of gastroenteropancreatic NETs. Further studies in larger patient populations are warranted.

#	Concept	H-Index	Publications	Citations
1	Medicine	2	2	250
2	Cancer Therapeutics	2	2	250
3	Immunology	1	1	167
4	Pharmacology	1	1	83
5	Immunotherapy	1	1	167

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