[Somatostatin analogues in treatment of gastrointestinal and pancreatic neuroendocrine tumors].
Clinical application of natural somatostatin is limited due to its short effect (the half-life of the preparation is less than 3 min), and a rebound effect after its administration. For these reasons, synthetic analogues of somatostatin, among which sandostatin (octreotide acetate) was the first one, were developed. Other cyclic analogues with similar sensitivity and activity profile, such as lanreotide (somatulin), somatostatin-14, and SOM 230, have been developed as well. These preparations seem to possess certain antiproliferative activity. Somatostatin analogues may be administered in repeated hypodermic injections, or repeated or prolonged intravenous infusions. Long-acting intramuscular preparations (sandostatin LAR) are usually administered once in four weeks, while long-acting lanreotide (somatulin) is administered once in two weeks. Sandostatin therapy is indicated to patients with functionally active neuroendocrine tumors of the stomach, duodenum, small bowel, or appendix. Glucagonomas, vipomas, and, to a lesser degree, gastrinomas and metastatic insulinomas are examples of functionally active endocrine pancreatic tumors that should be treated with sandostatin. Patients are selected according to a positive result of OcreoScan test. Other syndromes, which should be treated with octreotide, include ectopic secretion of adrenocorticotropic hormone in Cushing syndrome, oncogenic osteomalacia, and hypercalciemia resulting from ectopic secretion of parathyroid-like peptide. In patients with an advanced carcinoid syndrome, the starting dose of sandostatin (ocreotide) is 150 mcgr administered three times a day in hypordermic injections during 10 to 14 days, after which sandostatin LAR is administered in a dose of 20 mg once a month. Sandostatin is usually administered for the life-term of the patient, exept cases of intractable adverse effects or the development of total insensitivity.