Gallium-68-DOTATATE PET/CT for phosphaturic mesenchymal tumor localization in suspected tumor-induced osteomalacia

Gallium-68-DOTA-Tyr3-Octreotate (Ga-68-DOTATATE) positron emission tomography/computed tomography (PET/CT) has recently been shown to have utility for the localization of phosphaturic mesenchymal tumors (PMT) that cause tumor-induced osteomalacia (TIO), a rare renal phosphate-wasting disorder. The aim of this study was to evaluate the accuracy of Ga-68-DOTATATE PET/CT in localizing PMTs causing TIO and to compare its performance with other functional imaging modalities. Prospective recruitment and retrospective chart review of 30 patients with suspected TIO and evaluation with Ga-68-DOTATATE PET/CT between 2017 and 2023 were conducted at a tertiary medical center. True positive (TP) lesions were defined by histological confirmation of PMT. There were 22 TP lesions identified among 18 patients, with a mean SUV_max of 16.8 (±10.9). Sensitivity, specificity, and accuracy of Ga-68-DOTATATE PET/CT were 85.7%, 77.8%, and 83.3% on patient-based analysis, and 84.6%, 56.3%, and 73.8% on lesion-based analysis. Lesions such as subacute fractures, parathyroid adenomas, thymus uptake, vertebral hemangiomas, bone enchondromas, liver hemangiomas, and avascular necrosis were some of the pitfalls in interpretation. Ga-68-DOTATATE PET/CT led to a significant impact on clinical management in 24 (80%) of patients. The presence of DOTATATE-avid fractures was significantly associated with a localizing scan on univariable (OR 15.0, 95% CI 2.80-110, p = .001) and multivariable analysis (OR 9.45, 95% CI 1.33-98.4, p = .003). Ga-68-DOTATATE PET/CT has good accuracy for the localization of TIO, with superior sensitivity compared to F-18-FDG PET/CT. This significantly impacted clinical treatment decisions. Although DOTATATE-avid fractures may be a source of false positives, they may also indicate a higher probability of a localizing study.