68Ga-DOTATATE PET/CT for Detection and Evaluation of the Causative Tumor of Oncogenic Osteomalacia

Oncogenic osteomalacia, or tumor-induced osteomalacia, is a rare, serious paraneoplastic syndrome. It is predominantly driven by a small, benign mesenchymal tumor. The disease is readily prompted by the clinical features such as hyperphosphaturia, hypophosphatemia, low serum vitamin D3 levels, elevated serum fibroblast growth factor 23 levels, and osteomalacia. However, the causative tumor is frequently hidden in an unusual anatomical site and often goes undetected by conventional imaging, such as computed tomography (CT), while a permanent cure of the disease will only rely on exact localization and completely removal of the tumor.

Since mesenchymal tumors express somatostatin receptors (SSR), molecular imaging using radiolabeled somatostatin analogs may be one of the best ways to detect the small, occult tumors. 111In- and 99mTc-labeled octreotide and analogs have been proved useful to detect mesenchymal tumor and other SSR-positive tumors. However, the scintigraphy is insufficient to provide high-resolution images and precise anatomical information. In this study, a novel approach was proposed for exact localization of mesenchymal tumors through positron emission tomography (PET) imaging with 68Ga-DOTATATE and co-registration with CT. 68Ga-DOTATATE PET/CT is a novel method that might have improved sensitivity and resolution specifically for SSR-positive tumors, including the causative tumor of oncogenic osteomalacia.

The investigators will scan the patients in suspicion of oncogenic osteomalacia and the confirmed oncogenic osteomalacia patients in suspicion of relapse or with residual tumor after surgery, and compare it to 99mTc-HYNIC-TOC SPECT/CT and 18F-FDG PET/CT of the same patients. The aim of the study was to see if 68Ga-DOTATATE PET/CT can detect more tumors with higher resolution and more exact localization, and then help to develop optimal treatment strategy and improves patient care.