ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2019) 63 P1059 | DOI: 10.1530/endoabs.63.P1059

The expression of somatostatin receptor subtypes in immunohistochemistry and the response to somatostatin analogue therapy in non-functioning pituitary adenomas

Natalia Bozena Zawada & Jolanta Kunert-Radek

Department of Clinical Endocrinology, Medical University of Lodz, Lodz, Poland.

Introduction: Non-functioning pituitary adenomas (NFPA) are characterised by the expression of somatostatin receptors (SSTR), which is analysed using immunohistochemical investigations. The presence of SSTR forms the basis for the clinical use of somatostatin analogues (SSA) in the treatment of these tumours.

Aim: The study was undertaken to provide immunohistochemical analysis of SSTR and to correlate it with tumoral response to SSA therapy in NFPA.

Material and methods: Immunohistochemistry of SSTR in surgically removed tumour tissues was performed in 43 patients with NFPA. Expression of SSTR2 and STTR5 enabled to select a group of 17 patients after incomplete surgery who were treated with SSA (octreotide 20–30 mg intramuscular or lanreotide 120 mg subcutaneously every 28 days) for 2–10 years.

Results: Immunohistochemistry showed the presence of all SSTR with most common expression of SSTR5 (93%), SSTR2A (83.7%) and SSTR1 (83.7%). However, strong immunostaining was observed more frequently for SSTR1 and SSTR3 receptors. Considering patients treated with SSA, stabilisation of tumour size was noted in the majority of cases (88.24%). Adenoma shrinkage was confirmed with the use of magnetic resonance imaging in 2 patients.

Conclusions: Somatostatin analogues may be considered a therapeutic option for patients with NFPA after incomplete surgery. The expression of SSTR is a good predictive parameter for evaluation of SSA efficacy in NFPA. However, strong expression of SSTR1 and SSTR3 suggest that introduction of new, broad-spectrum somatostatin analogues may be more effective in the reduction of tumour size.

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