Treatment of neuroendocrine tumors with somatostatin analogs

Abstract

Neuroendocrine tumors constitute a group of hormone producing tumors originating from neuroendocrine cells in different organs. Most tumors have a low proliferation index measured by Ki67 and the progression of the tumor is slow. However, many patients suffer from endocrine symptoms induced by the hormones produced and released by the tumor cells. For some patients these symptoms can be life- threatening as in midgut carcinoid patients suffering from carcinoid crises with extensive flushes and hypotension or in patients with severe diarrhea induced by tumors producing vasointestinal polypeptide. In many other patients the hormone-induced symptoms interfere with the ability to carry out ordinary daily activities. The introduction of somatostatin analogs in the treatment of these hormone related symptoms has made it possible to control most of them and has added significantly to the quality of life for this group of patients. Unfortunately, the clinical inhibitory effect on tumor growth has not been very good with only 5-10% of the patients showing an objective response. However, stabilization of tumor growth may be achieved in a significant number of patients. In the future, the hope is that development of new somatostatin analogs with broader receptor-binding profiles will give us new analogs which are more efficient with regard to their antiproliferative effect. This possibility will be studied in future trials.

Clinicopathologic characteristics of pancreatic neuroendocrine tumors and relation of somatostatin receptor type 2A to outcomes

“…Somatostatin receptors are classified into 5 subtypes, and SSTR‐2 is subclassified into 2 variants according to the presence or absence of splicing: SSTR‐2a and SSTR‐2b . SSTR‐2a has been implicated in the inhibition of endocrine hormone secretion, the suppression of growth factor‐induced cell cycle progression, and the induction of apoptosis . Octreotide, a drug that binds with high affinity to SSTR‐2a, was developed to take advantage of these effects .…”

“…10,11 SSTR-2a has been implicated in the inhibition of endocrine hormone secre-tion, the suppression of growth factor-induced cell cycle progression, and the induction of apoptosis. [11][12][13] Octreotide, a drug that binds with high affinity to SSTR-2a, was developed to take advantage of these effects. 3 Recent studies have demonstrated the therapeutic usefulness of octreotide in patients with unresectable, well differentiated PNETs.…”

Differentiated expression of somatostatin receptor subtypes in experimental models and clinical neuroblastoma

“…SS analogs are used in the treatment of adult neuroendocrine tumors with good biochemical and clinical response 34. Recently, it has also been shown that the SS analog octreotide LAR has an antiproliferative effect in small intestinal endocrine tumors prolonging the time to progression significantly as compared to placebo treatment 35.…”

Effects of Somatostatin Analogs on a Growth Hormone-Releasing Hormone Secreting Bronchial Carcinoid,in Vivoandin VitroStudies

“…In patients with acromegaly and other neuroendocrine tumors, treatment with SAs can stabilize tumor growth or even induce tumor shrinkage (28,29). With respect to GHRH-secreting carcinoids, data are limited.…”