Analysis of somatostatin receptor 2A immunohistochemistry, RT-qPCR, and in vivo PET/CT data in patients with pancreatic neuroendocrine neoplasm

Daniel Kaemmerer, Ralph M. Wirtz, Elke K. Fischer, Merten Hommann, Jörg Sänger, Vikas Prasad, Elisa Specht, Richard P. Baum, Stefan Schulz, Amelie Lupp

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

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 [SUV max ], mean standard uptake values [SUV mean ]) 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 SUV max (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 SUV mean 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 SUV max correlated moderately with SSTR2A protein expression (C = 0.44, P = 0.03) and mRNA expression (C = 0.64, P = 0.042). Conclusions The SUV max and SUV mean 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.

Original languageEnglish
Pages (from-to)648-654
Number of pages7
JournalPancreas
Volume44
Issue number4
DOIs
StatePublished - May 25 2015

Keywords

  • immunohistochemistry
  • molecular imaging
  • pancreatic neuroendocrine tumor
  • somatostatin receptor
  • SSTR2A

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