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

4174 Background: Diagnostic imaging is critical in the 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). (SARTATE; at 4 ± 1 h and 20 ± 4 h post-injection) were assessed by two independent blinded central readers, and . Discordant lesions (only present on either DOTATATE or SARTATE PET/CT) were subsequently evaluated by an independent assessor against a standard of truth (SOT; biopsy and/or follow-up conventional imaging). The per-lesion sensitivity (SE) for discordant lesions was calculated for both SARTATE and DOTATATE (SE=proportion of true positive foci / [true positive foci + false negative foci]). Lesion detection rate (DR) was calculated for a composite (best-case scenario) lesion detection across both SARTATE time points and for DOTATATE (DR= total number of lesions detected on scan / total number of lesions on scan pair). Values express the averages across readers and both PET/CT time points (for SARTATE). Results: 45 participants were enrolled and received SARTATE (41 known and 4 suspected NETs). Most 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 participants; 223 of these were detected by SARTATE alone and 15 by DOTATATE alone. For the 122 discordant foci with evaluable SOT, the difference in SE 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<0.001). The lesion DR was 97.2% [95% CI 75.9, 99.5] for SARTATE and 44.4% [95% CI 32.3, 57.5] for DOTATATE. The liver had the highest number of foci detected by both tracers (352 foci on SARTATE vs. 180 on DOTATATE) among all regions. Seven (15.6%) participants experienced 9 SARTATE-related AEs; 8 were Grade 1 and one was Grade 2, with most resolving within 2 days. Conclusions: 64 Cu-SARTATE was found to be safe and well-tolerated in patients with GEP-NETs. SARTATE lesion detection was higher than that of DOTATATE, with the liver having the highest number of lesions identified. SARTATE was able to detect additional true positive lesions compared to DOTATATE. The enhanced diagnostic performance offered by SARTATE, especially in key organs affected by GEP-NETs, may have important clinical implications to inform treatment decisions. A phase III study of 64 Cu-SARTATE in NETs is being planned. Clinical trial information: NCT04438304 .