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Somatostatin receptors serve as viable markers in bronchopulmonary neuroendocrine neoplasms
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Somatostatin receptors may have utility as diagnostic, prognostic and therapeutic markers of bronchopulmonary neuroendocrine neoplasms, according to research published in The Journal of Clinical Endocrinology & Metabolism.
“Bronchopulmonary neuroendocrine tumors are different in diagnostics and treatment from gastroenteropancreatic neuroendocrine tumors,” Daniel Kaemmerer, MD, of the department of general and visceral surgery at Zentralklinik Bad Berka in Germany, told Endocrine Today.
Daniel Kaemmerer
The differences in the expression profiles of somatostatin receptors (SSTR) among the three types of bronchopulmonary neuroendocrine neoplasms (BP-NEN) could help establish a diagnostic cut-off and predict prognosis of patients, the researchers suggest.
“The distribution of somatostatin receptor subtypes, which are the basis for metabolic imaging (PET) and peptide-related radionuclide therapy (PRRT), are completely different between bronchopulmonary and gastroenteropancreatic neuroendocrine tumors,” Kaemmerer said.
German researchers examined 240 formalin-fixed, paraffin-embedded specimens from patients with typical carcinoid tumors (n=26), atypical carcinoid tumors (n=30) and small cell lung cancer (n=34) patients.
After tumor removal, the researchers retrospectively conducted immunohistochemical research using monoclonal antibodies that were generated in rabbits, with evaluation based on immunoreactive score. Additional real-time reverse transcription polymerase chain reaction mRNA analysis was conducted on adjacent slides gathered from 20 samples of each tumor type.
SSTR were present in most tumor sections, both at protein and mRNA level, but with different expression patterns.
“Both methods demonstrated equivalent results and correlated significantly to each other,” Kaemmerer said.
SSTR1 was detected in approximately 65% of typical and atypical carcinoids but rarely appeared in the small cell lung cancer samples. SSTR2A and SSTR5 were present in approximately 45% of all patient samples.
“In patients with small cell lung cancer, somatostatin-receptors subtype 2A was expressed in strong expression in 45% of the cases,” Kaemmerer said. “Hence, this subgroup of patients may benefit from an (additional) octreotide-based therapy.”
SSTR1 expression in patients with BP-NEN was associated with better patient survival.
“Studies and results in patients with gastroenteropancreatic neuroendocrine tumors cannot be equally assigned to patients with bronchopulmonary neuroendocrine tumors,” Kaemmerer said.
The peptides currently used in somatostatin analogues for PET imaging — DOTA-TOC, DOTA-TATE, DOTA-NOC — are not suitable for sufficient imaging of BP-NEN.
“The binding affinities of the peptides to the frequently detected SSTR-subtypes (SSTR1 and 5) are very low,” Kaemmerer said. “These data should be proven in further clinical studies.” – by Allegra Tiver
For more information:
Daniel Kaemmerer, MD, can be reached at Zentralklinik Bad Berka GmbH, Robert-Koch-Allee 9, 99437 Bad Berka, Germany; email: Daniel.Kaemmerer@zentralklinik.de.
Disclosure: The researchers reported no relevant financial disclosures.
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