First Clinical Evidence That Imaging with Somatostatin Receptor Antagonists Is Feasible

Abstract

Preclinical studies have indicated that somatostatin receptor (sst)–expressing tumors demonstrate higher uptake of radiolabeled sst antagonists than of sst agonists. In this study, we evaluated whether imaging with sst antagonists was feasible in patients. Methods: Biodistribution and tumor uptake of the sst antagonist ¹¹¹In-DOTA-pNO₂-Phe-c(DCys-Tyr-DTrp-Lys-Thr-Cys)DTyrNH₂ (¹¹¹In-DOTA-BASS) were studied in 5 patients with metastatic thyroid carcinoma or neuroendocrine tumors. Findings were compared with ¹¹¹In-pentetreotid (¹¹¹In-DTPA-octreotide) scan. Results: No adverse effects of ¹¹¹In-DOTA-BASS (20 μg) were observed. ¹¹¹In-DOTA-BASS detected 25 of 28 lesions, whereas ¹¹¹In-DTPA-octreotide detected only 17 of 28 lesions. In the same patient, ¹¹¹In-DOTA-BASS showed higher tumor and lower renal uptake than ¹¹¹In-DTPA-octreotide (3.5 ± 2.8 percentage injected activity [%IA] vs. 1.0 ± 0.99%IA and 1.5 ± 0.3 %IA vs. 2.3 ± 0.7 %IA) at 4 h after injection. Conclusion: Imaging of neuroendocrine tumors with sst antagonists is clinically feasible. The favorable human biodistribution data suggest that sst antagonists could significantly affect peptide receptor–mediated imaging and therapy.