Clinical review 23: The use of the long-acting somatostatin analog octreotide in the treatment of gut neuroendocrine tumors.

The SRIF analog octreotide (SMS 201-995) has been in clinical use for over 6 yr in the treatment of acromegaly and metastatic endocrine pancreatic and carcinoid tumors. The use of the analog in the treatment of acromegaly and TSH-secreting tumors is beyond the scope of this clinical review. Patient acceptance of the analog, given chronically by the sc route, has been excellent and side effects have been few with the exception of the development of gallstones. In endocrine pancreatic and carcinoid tumors the hypersecretion of hormones such as VIP, glucagon, and gastrin and the secretory products of carcinoid tumors (e.g. 5-hydroxytryptamine and tachykinins) and their clinical effects may be successfully blocked. This allows excellent palliation of such tumors and often enables the patients to return home and lead normal social lives. Initial hopes that long-term octreotide therapy would be an effective antitumor drug, reducing tumor growth, based on experimental animal models and human tumor cell lines, have not been born out in clinical practice. A reduction in gut tumor bulk due to octreotide, rarely or never occurs as a sustained phenomenon. Eventually a decrease in, and finally an absence of, clinical effectiveness occurs despite the reintroduction of other treatment modalities.