title: Somatostatin receptor based PET/CT imaging with 68Ga-DOTA-Nal3-octreotide for localization of clinically and biochemically suspected insulinoma.
abstract: BACKGROUND
  Localization of primary tumor in insulinoma is often difficult. We evaluated the role of 68Ga-DOTA-Nal3-Octreotide (DOTANOC) PET/CT for localization of primary tumor in patients with clinical and biochemical suspicion of insulinoma.
  
  
  METHODS
  Data of 35 patients (age: 38.4±16.5 years) who underwent 68Ga-DOTANOC PET/CT for clinical and biochemical suspicion of insulinoma (hypoglycemia, raised serum insulin and C-peptide levels) were retrospectively analyzed. PET/CT images were evaluated visually and semiquantitatively (SUV) by two experienced nuclear medicine physicians. A definite lesion in pancreas on non contrast CT showing increased 68Ga-DOTANOC was taken as positive. In the absence of CT lesion focal 68Ga-DOTANOC uptake in the pancreas more than liver was taken as positive. All patients had also undergone conventional imaging (CIM) (CT/MRI/endosonography) and their reports were retrieved for comparison. Histopathology and/or imaging/clinical/biochemical follow up (minimum 6 months) was used as reference standard.
  
  
  RESULTS
  The mean serum insulin levels was 51.6±54 µIU/mL and C-peptide level was 6.9±7.3 ng/mL. 68Ga-DOTANOC PET/CT was interpreted as positive in 11 patients (31.5%) and negative in 24 (68.5%). PET/CT demonstrated total 16 pancreatic lesions in 11 patients. In two patients it also showed both liver and lymph nodal metastases. 68Ga-DOTANOC PET/CT was true positive in 8, true negative in 1, false positive in 3 and false negative in 23 patients. Per patient based sensitivity of PET/CT was 25.8% (95% CI: 11.8-44.6), specificity was 25% (95% CI: 0.6-80.5) and accuracy was 25.7%. The mean SUVmax of pancreatic lesions was 13.8±11.1. On comparison no significant difference was seen between CIM and PET/CT on patient based (P=1.00) or lesion based comparison (P=0.790).
  
  
  CONCLUSIONS
  68Ga-DOTANOC PET/CT has limited utility for localizing the primary tumor in patients with clinical and biochemical suspicion of insulinoma. However, it might be useful for differentiating benign and malignant insulinoma. Further prospective comparative studies are warranted.
authors.affiliation: Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India - rkphulia@yahoo.com.
authors.forename: Punit
authors.initials: P
authors.lastname: Sharma
authors.forename: Saurabh
authors.initials: S
authors.lastname: Arora
authors.forename: Sellam
authors.initials: S
authors.lastname: Karunanithi
authors.forename: Rajesh
authors.initials: R
authors.lastname: Khadgawat
authors.forename: Prashant
authors.initials: P
authors.lastname: Durgapal
authors.forename: Raju
authors.initials: R
authors.lastname: Sharma
authors.forename: Devasenathipathy
authors.initials: D
authors.lastname: Kandasamy
authors.forename: Chandrasekhar
authors.initials: C
authors.lastname: Bal
authors.forename: Rakesh
authors.initials: R
authors.lastname: Kumar
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D006801:Humans; D007340:Insulinoma / Q000000981:diagnostic imaging* / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009942:Organometallic Compounds; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D000072078:Positron Emission Tomography Computed Tomography; D017481:Receptors, Somatostatin / Q000378:metabolism*; D055815:Young Adult
chemical_list: C504894:68Ga-DOTANOC; D009942:Organometallic Compounds; D017481:Receptors, Somatostatin