title: Analysis of somatostatin receptor 2A immunohistochemistry, RT-qPCR, and in vivo PET/CT data in patients with pancreatic neuroendocrine neoplasm.
abstract: OBJECTIVE
  Gallium 68 somatostatin receptor (SSTR) positron emission tomography/computed tomography (PET/CT) is one of the most sensitive imaging methods for pancreatic neuroendocrine tumors. The aim of the study was to correlate the receptor density generated from the static PET/CT (maximum standard uptake values [SUVmax], mean standard uptake values [SUVmean]) with subtype 2A SSTR (SSTR2A) immunohistochemistry and reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) gene-expression data.
  
  
  METHODS
  Thirty-nine tumor specimens (17 primary pancreatic tumors [PTs], 22 metastases [MTS]) of 19 patients with PET/CT scans preoperatively were evaluated. Subtype 2A SSTR expression was quantified immunohistochemically (immunoreactive score [IRS]) and on messenger RNA (mRNA) level by RT-qPCR.
  
  
  RESULTS
  The PT and MTS did not differ significantly in their SUVmax (P = 0.07) but displayed a dissimilarity with respect to their SSTR2A expression (mean [SD] IRS PT, 8.8 [3.6] vs mean [SD] IRS MTS, 5.1 [4.5]; P = 0.02).The SUVmean was highly significantly correlated to SSTR2A mRNA expression (C = 0.85, P < 0.001) and moderately to SSTR2A protein expression (C = 0.53, P = 0.05). Moreover, the SUVmax correlated moderately with SSTR2A protein expression (C = 0.44, P = 0.03) and mRNA expression (C = 0.64, P = 0.042).
  
  
  CONCLUSIONS
  The SUVmax and SUVmean are reliable ex vivo parameters for in vivo quantification of SSTR expression in pancreatic neuroendocrine tumors. Both immunohistochemistry and RT-qPCR are comparable methods for SSTR2A quantification. The PT and MTS differ significantly in their SSTR2A expression. This fact should be taken into account when treating patients with somatostatin analogs or peptide receptor radionuclide therapy.
authors: From the *Department of General and Visceral Surgery, Zentralklinik Bad Berka, Bad Berka; †STRATIFYER Molecular Pathology GmbH, Cologne; ‡Laboratory of Pathology and Cytology, Bad Berka; §Department of Nuclear Medicine, University Hospital Charité, Berlin; ∥Department of Pharmacology and Toxicology, Jena University Hospital, Friedrich Schiller University, Jena; and ¶Department of Molecular Radiotherapy and Molecular Imaging, Center for PET, Zentralklinik Bad Berka, Bad Berka, Germany.
authors: Daniel
authors: D
authors: Kaemmerer
authors: Ralph M
authors: RM
authors: Wirtz
authors: Elke K
authors: EK
authors: Fischer
authors: Merten
authors: M
authors: Hommann
authors: Jörg
authors: J
authors: Sänger
authors: Vikas
authors: V
authors: Prasad
authors: Elisa
authors: E
authors: Specht
authors: Richard P
authors: RP
authors: Baum
authors: Stefan
authors: S
authors: Schulz
authors: Amelie
authors: A
authors: Lupp
mesh_terms: D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism*; D005260:Female; D005710:Gallium Radioisotopes; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009362:Neoplasm Metastasis; D018358:Neuroendocrine Tumors / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D010190:Pancreatic Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D060888:Real-Time Polymerase Chain Reaction; D017481:Receptors, Somatostatin / Q000378:metabolism*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
chemical_list: D014408:Biomarkers, Tumor; D005710:Gallium Radioisotopes; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; C574734:SSTR2 protein, human