Management of Neuroendocrine Tumors: Current and Future Therapies

Kjell E Öberg

Disclosures

Expert Rev Endocrinol Metab. 2011;6(1):49-62. 

In This Article

Medical Management of NETs: Somatostatin Analogues

As curative surgery is generally not possible, many patients require chronic postoperative medical management to relieve symptoms and to suppress tumor growth and spread. Somatostatin is an endogenous inhibitor of various hormones secreted from the endocrine system. It binds with high affinity to the five somatostatin receptor subtypes (sst1–5) on secretory endocrine cells,[33] which have different inhibitory effects in the body (Table 4). Subtypes sst2 and sst5 are the most important in inhibiting hormonal secretions in functioning NETs due to their wide-ranging effects; it is thought the dual inhibition of both subtypes may have an increased inhibitory effect.[34] The two subtypes may also mediate antiproliferative effects.

Somatostatin has limited clinical use due to its short half-life (<3 min). Therefore, specific somatostatin analogues have been developed that work as receptor agonists and block hormone release. These analogues form the first-line medical therapy for well-differentiated NETs.[12] Octreotide (Sandostatin®, Novartis, Basel, Switzerland), the first somatostatin analogue available commercially, is a sst2-preferring agonist that also has moderate affinity for sst3 and sst5. It has a different chemical structure to somatostatin and a much longer half-life of 2 h. Lanreotide (Somatuline®, Ipsen, Paris, France) was the second analogue available and has a similar binding profile to octreotide. SOM230 (Pasireotide®, Novartis, Basel, Switzerland) is a novel multireceptor ligand analogue that has high affinity for four of the five somatostatin receptor subtypes (sst1, 2, 3 and sst5);[35,36] it has 40-fold higher affinity and 158-fold higher functional activity for sst5 than octreotide.

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