Trial Information

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.