title: Comparison of 18F-FDG and 68Ga DOTATATE PET/CT in localization of tumor causing oncogenic osteomalacia.
abstract: BACKGROUND
  Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome, usually caused by small benign mesenchymal tumors. The localization of these tumors is challenging, however, essential for the management. We compared the utility of F-FDG PET/CT and Ga DOTATATE PET/CT to detect the site of primary tumor in patients with suspicion of TIO.
  
  
  METHODS
  Retrospective analysis of 6 patients with hypophosphatemic osteomalacia and suspicion of TIO was performed. Ga DOTATATE PET/CT study was performed in all 6 patients to localize the tumor. F-FDG PET/CT was performed in 4 of 6 patients. F-FDG and Ga DOTATATE PET/CT studies were performed within 1 week of each other. Both studies were interpreted blindly without the knowledge of other imaging findings.
  
  
  RESULTS
  All patients had symptoms of osteomalacia and hypophosphatemia. All except 1 patient had increased level of fibroblast growth factor 23. The lag time (symptoms to PET diagnosis) ranged from 1.5 to 22 years. In 4 patients, where both studies were performed, F-FDG and Ga DOTATATE PET/CT were able to localize the tumor in 2 and 3 patients. Ga DOTATATE PET/CT detected tumor in 5 (83.3%) of 6 patients.
  
  
  CONCLUSIONS
  Ga DOTATATE PET/CT performed better than F-FDG PET/CT and is useful in the detection of tumors causing oncogenic osteomalacia. Therefore, in clinically suspected cases of hypophosphatemic osteomalacia, Ga DOTATATE PET/CT may be performed as first-line imaging investigation to avoid delay in the treatment of this devastating but curable disease. However, further studies with large patient population are warranted to validate our data.
authors.affiliation: From the Departments of *Nuclear Medicine and PET, and †Endocrinology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Kanhaiyalal
authors.initials: K
authors.lastname: Agrawal
authors.forename: Sanjay
authors.initials: S
authors.lastname: Bhadada
authors.forename: Bhagwant Rai
authors.initials: BR
authors.lastname: Mittal
authors.forename: Jaya
authors.initials: J
authors.lastname: Shukla
authors.forename: Ashwani
authors.initials: A
authors.lastname: Sood
authors.forename: Anish
authors.initials: A
authors.lastname: Bhattacharya
authors.forename: Anil
authors.initials: A
authors.lastname: Bhansali
mesh_terms: D000328:Adult; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009372:Neoplasms, Connective Tissue / Q000000981:diagnostic imaging*; D009942:Organometallic Compounds; D010018:Osteomalacia; D010257:Paraneoplastic Syndromes; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D014057:Tomography, X-Ray Computed
chemical_list: D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; C513399:gallium Ga 68 dotatate