Background: For tumors that express somatostatin receptors (SSTR), radiolabeled somatostatin analogs, such as 111In-pentetreotide, can demonstrate the presence of tumor by radioligand uptake using somatostatin receptor scintigraphy (SRS). The use of 111In-pentetreotide for SRS depends on the specific high affinity of octreotide for SSTR subtypes 2, 3, and 5. Of these, SSTR2 has the greatest affinity for octreotide and the greatest relevance for tumor detection with Octreoscan imaging. Discriminating between postoperative changes and residual or recurrent tumor after extensive skull base surgery is often difficult, but in a case of recurrent esthesioneuroblastoma (ENB) we found the use of Octreoscan imaging clinically useful. To better define the general relevance of this imaging technique in this setting, we analyzed SSTR subtype expression in a panel of ENB tumors.
Methods: The case history and correlations between MRI and 111In-pentetreotide SRS of a patient with recurrent ENB were reviewed. The expression pattern of the SSTR subtypes in a panel of ENB tumors was then analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) to better define the potential of more general use of Octreoscan for imaging ENB. To correlate SSTR2 protein expression with 111In-pentetreotide uptake, immunohistochemistry to detect SSTR2 was performed on tumor samples from regions of increased uptake on Octreoscan.
Results: The SSTR2 message was expressed at high levels in all five ENB tumor samples, and either SSTR2 protein or histologic findings typical for ENB were found in all tumor tissue obtained from regions of increased 111In-pentetreotide uptake. Furthermore, Octreoscan imaging in this case proved useful in clinical decision making.
Conclusion: The expression pattern of SSTR2 and the specificity of the Octreoscan for regions of active tumor growth support further investigation of the utility of Octreoscan imaging in the diagnosis and surveillance of ENB. Recent advances in novel therapies based on SSTR ligand binding also provide the rationale to consider such novel therapeutic approaches in patients with ENB.
Copyright 2005 Wiley Periodicals, Inc.