Improving the Somatostatin Receptor Status Assessment for Personalized and Precise Management of Neuroendocrine Neoplasms with the Use of a 99mTc-Radiolabeled Somatostatin Receptor Antagonist: The Final Results of the ERA PerMed TECANT Clinical Trial.

Neuroendocrine neoplasms (NENs) are a heterogeneous group of neoplasms in which an adequate expression of a somatostatin receptor (SSTR) serves as a target for imaging and therapy, typically using SSTR agonists. In the past decade, research in the field of NENs has focused on SSTR antagonists because of their higher and more sustained binding to a target, which may expand current diagnostic and therapeutic options, especially in patients with lower SSTR expression. The aim of this study was to perform a first-in-human injection of a novel 99mTc-labeled SSTR type 2 antagonist to establish safety, pharmacokinetics, and first assessment of SSTR status in patients with NENs through a qualitative and quantitative comparison with 68Ga-SSTR PET as a reference standard. Methods: Patients with metastatic grade 1 or 2 NENs and proven SSTR expression in primary and metastatic lesions on SSTR PET were imaged after a first-in-human injection of [99mTc]Tc-TECANT1. Assessment of safety, pharmacokinetics, and dosimetry was performed as a primary endpoint, with comparison of diagnostic performance and quantification of uptake to SSTR PET as a secondary endpoint. Results: Ten patients were enrolled. [99mTc]Tc-TECANT1 was found to be safe, with favorable pharmacokinetics and dosimetry (average total body effective dose of 3.3 ± 0.7 mSv). The diagnostic performance in comparison to that of SSTR PET was found to be superior, with a comparable or a higher number of detected lesions and superior target-to-background contrast (a factor of 2 and above for lesions with the highest uptake). Conclusion: [99mTc]Tc-TECANT1 appears to be a safe and widely utilizable radiopharmaceutical for the assessment of SSTR expression status in NENs. Validation of results in a larger cohort is warranted.