Molecular imaging with 68Ga-SSTR PET/CT and correlation to immunohistochemistry of somatostatin receptors in neuroendocrine tumours

Somatostatin receptors (SSTR) are known for an overexpression in gastroenteropancreatic neuroendocrine tumours (GEP-NET). The aim of the present study was to find out if the receptor density predicted by the semi-quantitative parameters generated from the static positron emission tomography (PET/CT) correlated with the in vitro immunohistochemistry using a novel rabbit monoclonal anti-SSTR2A antibody (clone UMB-1) for specific SSTR2A immunohistochemistry and polyclonal antibodies for SSTR1 and 3–5. Overall 14 surgical specimens generated from 34 histologically documented GEP-NET patients were correlated with the preoperative 68Ga-DOTA-NOC PET/CT. Quantitative assessment of the receptor density was done using the immunoreactive score (IRS) of Remmele and Stegner; the additional 4-point IRS classification for immunohistochemistry and standardized uptake values (SUVmax and SUVmean) were used for PET/CT. The IRS for SSTR2A and SSTR5 correlated highly significant with the SUVmax on the PET/CT (p