Management of Gastroenteropancreatic Endocrine Tumors: The Place of Somatostatin Analogues

Abstract

The place of the long-acting somatostatin analogue octreotide in the management of symptoms in patients with functional gastroenteropancreatic (GEP) tumors and of growth in patients with metastatic disease is reviewed in this report. Numerous studies indicate that octreotide is, currently, the therapeutic principle of first choice in the symptomatic treatment of patients with carcinoid syndrome, Verner-Morrison syndrome and glucagonoma syndrome but not of insulinoma and gastrinoma patients. A beneficial effect on tumor growth has been demonstrated in 40% of patients with metastatic GEP tumors with stabilization of the disease as the most favorable response. However, further studies have to identify subgroups of patients in whom octreotide alone or in combination with alpha-interferon inhibits tumor growth.

Treatment of advanced neuroendocrine tumours with the radiolabelled somatostatin analogue octreotide

“…Somatostatin is mainly an inhibitory peptide that has a very short half-life, approximately 2 minutes, which makes it unsuitable for routine clinical use 7,8 . Introduction of D-amino acids and shortening of the molecule to the bioactive core sequence resulted in the eight amino acids-containing somatostatin analogues 1,6,7 . Octreotide (Novartis, Basel, Switzerland) is the first somatostatin analogue to be used in clinical practice while considerable experience has also been obtained with lanreotide (Ipsen, Paris, France) and more recently vapreotide (Figure 1) …”

“…Scintigraphy with 111 In-pentetreotide is used for the diagnosis and staging of the tumours as well as identifying the patients who may be suitable for treatment with radiolabelled octreotide 1,4,7 . The detection of an unsuspected lesion in a patient with known metastatic spread usually has little impact on management.…”

“…Neuroendocrine tumours (NET) constitute a heterogeneous group of tumours which originate from the diffuse neuroendocrine system (DNES) and are programmed to adopt a specific neuroendocrine phenotype 1 . The system includes endocrine glands, such as the pituitary, the parathyroids and adrenal glands as well as endocrine islets within glandular tissue (thyroid or pancreatic) and cells disseminated between exocrine cells, such as endocrine cells of the digestive and respiratory tracts 2,3 .…”

“…Although NET may vary in clinical presentation, location and specific histology, they share common features which are detected by refined morphological techniques for endocrine granules, histochemical techniques for secretory peptides or amines and electron microscopy 3 . Some NET may occasionally exert a very aggressive behavior and become highly malignant (poorly-differentiated NET), but the great majority tend to be relatively slow growing (well-differentiated NET) and retain many multipotent differentiation capacities 1,3 . Such features include the possession of neuroamine uptake mechanisms and/or specific receptors at the cell membrane, such as somatostatin receptors, which can be of great value in identifying and localizing these tumours as well as in their therapy.…”

Treatment of advanced neuroendocrine tumours with radiolabelled somatostatin analogues

“…This system includes endocrine glands, such as the pituitary, the parathyroids and the adrenal medulla, as well as endocrine islets within glandular tissue (thyroid or pancreatic) and cells disseminated between exocrine cells, such as endocrine cells of the digestive and respiratory tracts (Arnold et al 1994, Kaltsas et al 2004a. The latter are usually known as 'carcinoid tumours', and, according to their anatomic site of origin, they have been classified as foregut, midgut and hindgut carcinoid tumours (Solcia et al 1999).…”