Is There an Additional Value of Using Somatostatin Receptor Subtype 2a Immunohistochemistry Compared to Somatostatin Receptor Scintigraphy Uptake in Predicting Gastroenteropancreatic Neuroendocrine Tumor Response?

Abstract

BACKGROUND AND AIMS:

It is unknown whether tumoral somatostatin receptor subtype 2a (sst2a) immunohistochemistry (IHC) has additional value compared to somatostatin receptor scintigraphy (SRS) uptake using OctreoScan® in predicting response to peptide receptor radiotherapy using 177Lu-octreotate (PRRT) in patients with gastroenteropancreatic neuroendocrine tumors (GEP-NETs). The aims of this study were: (1) to establish the percentage of sst2a immunopositivity in GEP-NET samples of PRRT-treated patients, (2) to determine the relationship between best GEP-NET response using RECIST 1.0 criteria 1 year after PRRT and tumoral sst2a IHC, and (3) to compare characteristics of patients with sst2a IHC-negative and -positive tumors.

METHODS:

All 73 consecutive patients were selected for PRRT based on a positive SRS. Radiological response was scored according to RECIST 1.0 criteria. sst2a status was detected on tumor samples by IHC.

RESULTS:

In total, 93% of GEP-NET samples showed sst2a IHC positivity. No statistically significant relationship was observed between in vitro sst2a expression and in vivo best GEP-NET response 1 year after PRRT (p = 0.47). Sex, primary tumor site, disease stage, ENETS TNM classification, Ki-67 index, highest serum chromogranin-A level, and highest neuron-specific enolase level were not significantly different between patients with negative and positive sst2a tumoral IHC with the exception of age at diagnosis (p = 0.007).

CONCLUSIONS:

sst2a IHC of tumor samples has no additional value compared to SRS uptake using OctreoScan® in predicting tumor response after PRRT.

• Authors: Roxanne C S van Adrichem, Kimberly Kamp, Carolien H M van Deurzen, Katharina Biermann, Richard A Feelders, Gaston J H Franssen, Dik J Kwekkeboom, Leo J Hofland, Wouter W de Herder
• Journal: Neuroendocrinology (Neuroendocrinology) Vol. 103 Issue 5 Pg. 560-6 ( 2016) ISSN: 1423-0194 [Electronic] Switzerland
• PMID: 26536001 (Publication Type: Journal Article)
• Copyright: © 2015 S. Karger AG, Basel.

Chemical References

• 177Lu-octreotate
• Antineoplastic Agents
• Receptors, Somatostatin
• SSTR2 protein, human
• Octreotide

Topics

• Adult
• Aged
• Antineoplastic Agents (therapeutic use)
• Female
• Gene Expression Regulation, Neoplastic (drug effects)
• Humans
• Immunohistochemistry
• Intestinal Neoplasms (diagnostic imaging, drug therapy, metabolism)
• Male
• Middle Aged
• Neuroendocrine Tumors (diagnostic imaging, drug therapy, metabolism)
• Octreotide (analogs & derivatives, therapeutic use)
• Pancreatic Neoplasms (diagnostic imaging, drug therapy, metabolism)
• Radionuclide Imaging
• Receptors, Somatostatin (metabolism)
• Stomach Neoplasms (diagnostic imaging, drug therapy, metabolism)
• Treatment Outcome