DISCO: Diagnostic performance of 64 Cu-SARTATE compared to 68 Ga-DOTATATE in patients with known or suspected neuroendocrine tumors with focus on liver findings.

618 Background: Diagnostic imaging is critical in the theranostic management of neuroendocrine tumors (NETs). 64 Cu-SARTATE may provide advantages over existing imaging agents due to its longer half-life and sarcophagine chelator, with a potential to accurately detect additional disease in NETs. Methods: This multi-center Phase II study assessed the safety and efficacy of 64 Cu-SARTATE (200 MBq) in participants with known or suspected gastroenteropancreatic (GEP)-NETs (NCT04438304). Standard of care 68 Ga-DOTATATE PET/CT (DOTATATE) was performed within 35 days prior to 64 Cu-SARTATE PET/CT (SARTATE; at 4 ± 1 hrs [same-day imaging] and 20 ± 4 hrs [next-day imaging] post-injection). Scans were assessed by two independent blinded central readers, and every abnormal focus (an abnormality that may be related to a GEP-NET and cannot be accounted for by a benign process) was recorded. Discordant lesions present on only one of the two PET scans (either DOTATATE or SARTATE) were subsequently evaluated by an independent assessor against a standard of truth (SOT; biopsy and/or follow-up conventional imaging). The per-lesion sensitivity for discordant lesions was calculated for both SARTATE and DOTATATE (defined as the proportion of true positive foci / [true positive foci + false negative foci]; primary endpoint). Values express the averages across readers and both PET/CT time points (for SARTATE). Safety was monitored using safety parameters typical of early phase trials. Results: 45 participants were enrolled and received SARTATE (41 known NETs and 4 suspected NETs). Most subjects had stage 3 or 4 disease. The mean number of foci detected by SARTATE was 441 vs. 227 by DOTATATE. A total of 238 discordant foci were identified in 34 subjects with scan pairs; 223 of these were detected by SARTATE alone and 15 by DOTATATE alone. For the 122 discordant foci with evaluable SOT, the difference in sensitivity for SARTATE vs. DOTATATE was statistically significant (94.7% [95% CI 65.1, 99.5] for SARTATE vs. 5.4% [95% CI 0.5, 34.9] for DOTATATE; p