68Ga-DOTATATE for Tumor Localization in Tumor-Induced Osteomalacia

Context: Phosphaturic mesenchymal tumors (PMTs) are small, typically difficult to localize, and express somatostatin receptors. Recent work suggests imaging studies using (68)Gallium (Ga-68)-conjugated somatostatin peptide analogues, such as 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) TATE, which enables somatostatin receptor imaging with positron emission tomography (PET), may be useful at identifying these tumors. Objective: Our objective was to evaluate the use of Ga-68-DOTATATE PET/computed tomography (CT) for tumor localization in tumor-induced osteomalacia (TIO). Design: This was a single-center prospective study of patients with TIO. Setting: The study was conducted at the National Institutes of Health Clinical Center between February 2014 and February 2015. Subjects: Eleven subjects (six females, five males) with TIO were included. Intervention: Subjects underwent Ga-68-DOTATATE PET/CT in addition to In-111-pentetreotide single-photon emission CT (Octreoscan-SPECT/CT) and fluorodeoxyglucose-PET/CT (F-18 FDG-PET/CT) scan. Main Outcome Measures: Localization of PMTs on the previously described imaging modalities were determined. Results: The tumor was successfully localized in 6/11 (54.5%) subjects (one was metastatic). The tumor was identified by Ga-68-DOTATATE in all six cases. Both Octreoscan-SPECT/ CT and F-18 FDG-PET each identified the tumor in 4/6. In no cases was Ga-68-DOTATATE the only imaging study to identify the tumor. Conclusions: In this first prospective study comparing Ga-68-DOTATATE PET/CT to Octreoscan-SPECT/ CT and F-18 FDG-PET in TIO localization, Ga-68-DOTATATE PET/CT demonstrated the greatest sensitivity and specificity, suggesting that it may be the best single study for localization of PMTs in TIO.