68 Ga-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 (68 Ga)-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 68 Ga-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 68 Ga-DOTATATE PET/CT in addition to 111 In-pentetreotide single-photon emission CT (Octreoscan- SPECT/CT) and fluorodeoxyglucose-PET/CT (18 F 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 68 Ga-DOTATATE in all six cases. Both Octreoscan-SPECT/CT and 18 F FDG-PET each identified the tumor in 4/6. In no cases was 68 Ga-DOTATATE the only imaging study to identify the tumor.

CONCLUSIONS: In this first prospective study comparing 68 Ga-DOTATATE PET/CT to Octreoscan-SPECT/CT and 18 F FDG-PET in TIO localization, 68 Ga-DOTATATE PET/CT demonstrated the greatest sensitivity and specificity, suggesting that it may be the best single study for localization of PMTs in TIO.