The corellation between somatostatin receptors expression and octreotide treatment in non-functioning pituitary adenomas

Abstract

Introduction. Neurosurgery, which is the treatment of choice of non-functioning pituitary adenomas (NFPA), is often incurative. It usually leaves tumour residue that can regrow in the future. There is no established management for the postoperative period of NFPA, however, some data suggest that somatostatin analogues (SSA) can be effective, especially regarding somatostatin receptors (SSTR) presence in NFPA. SSTR scintigraphy and immunohistochemistry are used to assess SSTR expression in NFPA.

Aim: to analyse the outcome of SSA treatment in NFPA and to correlate it with the results of SSTR scintigraphy and immunohistochemistry.

Material and methods. Twenty six NFPA patients after incomplete neurosurgery with positive results of scintigraphy and immunohistochemistry were included in the study. All patients were treated with octreotide LAR 20mg intramuscular every 4 weeks. The tumour size was evaluated in control magnetic resonance imaging after 2 years of SSA therapy.

Results. Tumour size remained stable in the majority of NFPA. Adenoma size reduction was observed in 2 patients with strong expression of SSTR2 in both scintigraphy and immunohistochemistry. Increase of tumour size was noticed in 4 patients whose tumours were characterised not only by the presence of SSTR2 and SSTR5 but also by strong expression of SSTR1 in immunohistochemistry.

Conclusions. Only strong expression of SSTR2 can predict patients response to SSA treatment in NFPA. However, strong expression of SSTR1 observed in some of NFPA gives hope that introduction of new broad spectrum SSA like pasireotide would be more effective, especially in tumour shrinkage.