Radioguided Surgery with Gallium 68 Dotatate for Patients with Neuroendocrine Tumors

Importance: Neuroendocrine tumors (NETs) express somatostatin receptors, which can be targeted with radiolabeled peptides. In a variety of solid tumors, radioguided surgery (RGS) has been used to guide surgical resection. Gallium 68 ( ⁶⁸ Ga) dota peptides have been shown to be more accurate than other radioisotopes for detecting NETs. A pilot study previously demonstrated the feasibility and safety of ⁶⁸ Ga-dotatate RGS for patients with NETs. Objective: To evaluate what intraoperative techniques and thresholds define positive lesions that warrant resection during ⁶⁸ Ga-dotatate RGS. Design, Setting, and Participants: This prospective cohort study, conducted between October 23, 2013, and February 14, 2018, included 44 patients with NETs who underwent ⁶⁸ Ga-dotatate RGS. Intervention: Gallium 68-dotatate RGS. Main Outcomes and Measures: The in vivo and ex vivo tumor to background ratio (TBR) was assessed for resected lesions and correlated with the histopathologic findings. Results: Forty-four patients (22 women and 22 men; mean [SD] age, 51.0 [13.7] years) had 133 lesions detected on preoperative imaging scans, with a diagnosis of a pancreatic NET (19 of 44 [43%]), gastrointestinal NET (22 of 44 [50%]), and pheochromocytoma or paraganglioma (3 of 44 [7%]). The TBR was obtained by normalizing to the omentum (106 of 133 [79.7%]) or other solid organs (27 of 133 [20.3%]). The omentum had a significantly lower mean (SD) count than other solid organs for background count activity 3 hours after injection (22.1 [17.0] vs 34.5 [39.0]; P <.001). The lesions containing NETs had a higher TBR than those that did not contain NETs (18.9 vs 4.4; P <.001). On a receiver operating characteristic curve analysis, a TBR of 2.5 had a sensitivity of 90% and a specificity of 25%, and a TBR of 16 had a sensitivity of 54% and a specificity of 81%. Conclusions and Relevance: A TBR of 2.5 or greater is a highly sensitive threshold for indicating a lesion to be consistent with a NET on histologic findings and thus warranting surgical resection. The omentum should be used as the background count activity for ⁶⁸ Ga-dotatate RGS for patients with abdominal NETs.