Somatostatin analogue (SMS 201-995) in the management of gastroenteropancreatic tumors and diarrhea syndromes

Postprandial Hypotension: An Underreported Silent Killer in the Aged

Orthostatic hypotension (OH) is one of the most common autonomic dysfunctions, with high prevalence in populations of elderly, hypertensive, diabetic, or Parkinson's patients. Evidence is emerging that OH co-occurs with postprandial hypotension (PPH); a greater prevalence of PPH than of OH is reported for Parkinson's disease patients. OH is diagnosed by measuring the blood pressure changes associated with postural changes and often produces alterations in consciousness or other such bothersome symptoms as fainting. PPH is diagnosed by measuring the blood pressure changes associated with ingesting high carbohydrate test meals. Because of the time lag between food ingestion and absorption, PPH is often not reported as symptomatic and, therefore, not diagnosed as PPH. OH and PPH are independent predictors for all causes of mortality. Relative underdiagnosis may qualify PPH as a "silent killer" disease. This review is aimed at providing updates on the epidemiology, pathophysiology, and clinical aspects associated with the diagnosis and treatment of PPH. Highlighting the current gaps in knowledge and research about PPH is expected to make medical practitioners more cognizant of the dangers of underdiagnosis and motivate future research to identify individuals and populations at high risk for PPH and its sequelae.

Advances in the Diagnosis and Management of Well-Differentiated Neuroendocrine Neoplasms

Neuroendocrine neoplasms constitute a diverse group of tumors that derive from the sensory and secretory neuroendocrine cells and predominantly arise within the pulmonary and gastrointestinal tracts. The majority of these neoplasms have a well-differentiated grade and are termed neuroendocrine tumors (NETs). This subgroup is characterized by limited proliferation and patients affected by these tumors carry a good to moderate prognosis. A substantial subset of patients presenting with a NET suffer from the consequences of endocrine syndromes as a result of the excessive secretion of amines or peptide hormones, which can impair their quality of life and prognosis. Over the past 15 years, critical developments in tumor grading, diagnostic biomarkers, radionuclide imaging, randomized controlled drug trials, evidence-based guidelines, and superior prognostic outcomes have substantially altered the field of NET care. Here, we review the relevant advances to clinical practice that have significantly upgraded our approach to NET patients, both in diagnostic and in therapeutic options.

Medical Treatment of Neuroendocrine Tumors

Background

Tumors of the neuroendocrine system are characterized by amine precursor uptake and decarboxylation, and they represent a heterogeneous group of carcinomas including carcinoids, islet cell carcinomas of the pancreas, medullary thyroid carcinomas and Merkel cell carcinomas. Their similar cytochemical and ultrastructural properties sustain the hypothesis of a common embryologic origin within the neural crest. Many of these tumors grow slowly, and reducing tumor burden represents the treatment of choice. However, when surgery is not feasible, medical treatment has to be considered. Therapeutic approaches in metastatic disease often do not consider the different biologic behaviors of these neoplasms. Moreover, efficacy of the treatment is associated with lack of a clear definition of the type of response: objective, symptomatic or biochemical.

Methods

In this review we have analyzed the different medical approaches used in the treatment of neuroendocrine tumors in an attempt to define their precise role in the different neoplasms.

Results

In carcinoid tumors, immunotherapy and the somatostatin analogue can be efficaciously used for the control of carcinoid syndrome. For inhibition of tumor growth, chemotherapy should be used only in patients with rapidly progressive disease, and the results are still unsatisfactory.

Conclusions

Although all these tumors appear to have similar cytochemical properties, the responsiveness of the various neoplasms is very different. In the future, a specific treatment modality and a clear definition of the type of response (objective, symptomatic or biochemical) need to be defined for each type of neuroendocrine tumor.

Sunitinib for the treatment of metastatic paraganglioma and vasoactive intestinal polypeptide-producing tumor (VIPoma)

OBJECTIVES

Gastroenteropancreatic neuroendocrine tumors (NETs) are rare tumors of the endocrine and nervous systems. Whereas early surgical resection can significantly reduce tumor mass, there are few data available concerning the control of hormonal secretion and associated symptoms. Studies have shown that the tyrosine kinase inhibitor sunitinib significantly prolongs progression-free survival in patients with pancreatic NETs. Here, we present 2 case reports of sunitinib in patients with different types of NETs.

METHODS

The patients were a 12-year-old boy with metastatic vasoactive intestinal polypeptide-producing tumor (VIPoma) and a 70-year-old woman with metastatic paraganglioma/NET. Both were treated in an outpatient clinical setting. Sunitinib was titrated to 37.5 mg on a continuous daily dosing schedule in the patient with VIPoma, and the dose was 50 mg/d (4 weeks on, 2 weeks off) in the patient with the paraganglioma/NET.

RESULTS

The patient with the paraganglioma/NET had a confirmed complete radiographic response and the patient with VIPoma had a confirmed partial response (Response Evaluation Criteria in Solid Tumors). In both patients, improvements were observed in biochemical tumor markers, clinical responses, and quality of life.

CONCLUSIONS

In these patients, sunitinib reduced biochemical markers and stabilized or reduced tumor bulk and may therefore be a potential therapeutic option for these tumor types.

Pharmacological management of diarrhea

According to the World Health Organization, there are approximately 2 billion annual cases of diarrhea worldwide. Diarrhea is the leading cause of death in children younger than 5 years and kills 1.5 million children each year. It is especially prevalent in the developing world, where mortality is related to dehydration, electrolyte disturbance, and the resultant acidosis, and in 2001, it accounted for 1.78 million deaths (3.7% of total deaths) in low- and middle-income countries. However, diarrhea is also a common problem in the developed world, with 211 million to 375 million episodes of infectious diarrheal illnesses in the United States annually, resulting in 73 million physician consultations, 1.8 million hospitalizations, and 3100 deaths. Furthermore, 4% to 5% of the Western population suffers from chronic diarrhea. Given the high prevalence of diarrhea, research has been directed at learning more about the cellular mechanisms underlying diarrheal illnesses in order to develop new medications directed at novel cellular targets. These cellular mechanisms and targets are discussed in this article.

Neuroendocrine tumors: a critical appraisal of management strategies

OBJECTIVES

This supplement represents the proceedings of a panel of investigators whose goal was to assess the quality of evidence pertaining to current therapeutic approaches in the management of neuroendocrine tumors (NETs). It will examine the differences in opinions between expert faculty and community physicians.

METHODS

The Neuroendocrine Tumors Summit convened in December 2009 to address 6 statements prepared by panel members that reflect important questions in the management of NETs.

RESULTS

Panel members were polled on their acceptance of each statement, and those results were compared with community-based oncologists, gastroenterologists, and endocrinologists.

CONCLUSIONS

More education regarding the treatment of NETs, including pertinent studies, is needed for physicians. Additional multicenter, prospective, placebo-controlled trials are necessary to demonstrate the benefits of somatostatin analogs, including their ability to control symptoms and affect tumor growth, and their synergistic effect with other therapies. New trials should be reported consistently and include time to tumor progression and progression-free survival as primary or secondary end points.

The role of somatostatin analogues in the treatment of neuroendocrine tumours

Neuroendocrine tumours belong to a heterogeneous family of neoplasms, originating in endocrine glands (such as the pituitary, parathyroid or the neuroendocrine adrenal glands), in endocrine islets (within the thyroid or pancreas) as well as in endocrine cells dispersed between exocrine cells throughout the digestive or respiratory tracts. The clinical behaviour of neuroendocrine tumours is variable; they may be functioning or not functioning, ranging from well-differentiated slow growing neuroendocrine tumours to poorly differentiated neuroendocrine tumours, which are highly aggressive malignant tumours. The development of somatostatin analogues as important diagnostic and treatment tools have revolutionised the clinical management of patients with neuroendocrine tumours. However, although symptomatic relief and stabilisation of tumour growth for various periods of time are observed in many patients treated with somatostatin analogues, tumour regression is rare. Development of new somatostatin analogues and new drug combination therapies should further improve the clinical management of these patients.

Characterization of somatostatin receptor subtypes

Somatostatin regulates endocrine and exocrine secretion, possesses antiproliferative properties and acts as a neurotransmitter/neuromodulator in the central nervous system. These effects are mediated by G protein-coupled receptors, of which at least five types have been cloned (sstr1-5). In radioligand-binding studies we have compared the binding properties of sstr1-5 with their activities as somatostatin receptors. All receptors identified so far bind somatostatin-14 and somatostatin-28 with high affinity. The similarities in receptor sequence and in the binding profiles of short synthetic somatostastin analogues such as octreotide, MK 678 or RC 160 for sstr1-5 indicate the existence of two classes of receptors sstr1/sstr4 with virtually no or very low affinity and sstr2/sstr3/sstr5 with intermediate to high affinity for the short somatostatin analogues. All five receptors mediate inhibition of adenylyl cyclase; this inhibition is sensitive to pertussis toxin. In vitro and in vivo studies suggest the importance of sstr2 and/or sstr5 in the inhibition of growth hormone release. The sstr2 receptor is apparently the predominant subtype expressed in somatostatin receptor-positive tumours. Evidence exists for the importance of sstr5 receptors in insulin secretion and sstr1 receptors in oncology. Somatostatin receptor-selective agonists and antagonists will help to explore new therapeutic opportunities in oncology as well as in endocrine and gastrointestinal disorders and those of the central nervous system.

Octreotide exerts only acute, but no sustained, effects on MRI enhancement of liver metastases in carcinoid syndrome

We have investigated the acute and sustained hemodynamic effects of octreotide on hepatic metastases of midgut carcinoids using contrast-enhanced dynamic magnetic resonance imaging (MRI). Seven patients with the carcinoid syndrome and metastasized midgut carcinoid tumors underwent functional dynamic multi-phase gadolinium-enhanced MRI of selected liver metastases at baseline and 60 min after the subcutaneous (s.c.) administration of 100 microg octreotide, and also after 3 months with three times daily (t.i.d.) 100 microg octreotide s.c. Baseline MRIs showed the typical aspect of carcinoid liver metastases with a very bright signal on the T2-weighted sequences and intense enhancement in the arterial phase after injection of gadolinium-diethylenetriaminepentaacetate. MRIs 60 min after the s.c. administration of 100 microg octreotide showed a 34.9 +/- 6.2% (mean +/- SD) reduction in relative enhancement in the selected liver metastases as compared to baseline. In 2 patients, however, there was no (significant) reduction in the relative enhancement in the selected liver metastases 60 min after the s.c. administration of 100 microg octreotide as compared to baseline. Only in 2 patients did the MRIs at 3 months show a decrease in relative enhancement in one of the selected liver metastases. At 3 months, with 100 microg octreotide s.c. t.i.d., there was no correlation between the change in relative enhancement on MRI and the change in 24-hour 5-HIAA excretion. There is thus only an acute effect of octreotide on the perfusion of liver metastases. This study further shows that contrast-enhanced dynamic MRI can be a very useful tool for studying hemodynamic effects of medical therapies on liver metastases in patients with metastatic midgut carcinoids.

Somatostatin analog therapy in treatment of gastrointestinal disorders and tumors

Long-acting octapeptide somatostatin analogs can effectively control symptoms resulting from excessive hormone release in patients with endocrine tumors of the gastrointestinal tract, provided that these tumors and metastases show a high expression of the somatostatin receptor subtype 2. The presence of this receptor subtype on these tumors can be demonstrated by in vitro studies, but also in vivo using 111In-pentetreotide scintigraphy. In a few studies, significant antiproliferative effects of these drugs on these tumors have also been demonstrated. The effectiveness of octapeptide somatostatin analogs in the management of chemotherapy- related and AIDS-related diarrhea and in reducing postoperative complications of pancreatic surgery have also been demonstrated. These drugs have been used to decrease the output of enterocutaneous pancreatic fistulas and are prophylactically used to prevent the development of these fistulas. Octapeptide somatostatin analog therapy is widely accepted for the initial management of acute variceal bleeding in cirrhotic patients. These drugs are currently also being evaluated for the treatment of advanced hepatocellular carcinoma and malignant intestinal obstruction. Radiotherapy with octapeptide somatostatin analogs coupled to radionuclides such as indium-111, yttrium-90, and lutetium- 177 is currently being studied in phase I-III trials.

Diagnostic, surgical and medical aspect of the midgut carcinoids

This review covers the incidence, prognosis, diagnosis and treatment of midgut carcinoids with emphasis on the surgical and peri-operative aspects. Midgut carcinoids are rare neuro-endocrine tumours which become manifest once they have metastasized to the liver. Treatment of metastatic disease may include radical resection but is usually palliative. The tumour grows relatively slow. Besides the biochemical effects resulting in the carcinoid syndrome, patients may suffer from mechanical mass effects of the tumour. Medical treatment can alleviate the biochemical effects of the tumour, but has a limited effect on tumour growth. The introduction of octreotide was a milestone in palliation of these symptoms and has led to more aggressive treatment protocols. Treatment aimed at cytoreduction of hepatic metastasis and diminished secretion of bioactive amines may achieve good palliation. Cytoreduction may be performed by means of surgery, hepatic arterial ligation, (chemo)embolization, cryosurgery, radio-frequency ablation, internal radiation or even liver transplantation. The role of these options will be discussed in this review.

Systematic review: the use of somatostatin or octreotide in refractory diarrhoea

BACKGROUND

Somatostatin and octreotide have multiple effects which make them ideal for treating diarrhoea of different aetiologies. Their use in a variety of conditions with refractory diarrhoea, however, is based on a limited number of studies.

AIM

We undertook a systematic review of the available English literature to maximize an evidence-based approach to the treatment of refractory diarrhoea. We tested the hypothesis that efficacy is independent of aetiology.

METHODS AND RESULTS

A Medline and individual article search from 1965 to 2000 was undertaken on the use of somatostatin and octreotide in diarrhoea. All reports containing at least five subjects were included. The percentage response in case series and randomized controlled trials was compared, and a meta-analysis of randomized controlled trials where patient level data were provided was carried out. There were 30 publications found (18 case series, 12 randomized controlled trials). The response percentage was 73% overall in case series and 64% in randomized controlled trials (not significant). A meta-analysis of nine randomized controlled trials revealed significant heterogeneity despite an overall relative risk of 0.5 (95% confidence interval, 0.27-0.91). Subgroup analysis of the largest aetiological groups showed that acquired immunodeficiency syndrome studies were homogeneous, but somatostatin and octreotide were less effective. Post-chemotherapy studies remained heterogeneous and somatostatin and octreotide were highly effective.

CONCLUSIONS

While this review strengthens the consensus guidelines on the use of somatostatin and octreotide for refractory diarrhoea, evidence-based support requires additional studies.

The surgical management of pancreatic neuroendocrine tumors

NETs of pancreas are rare and may or may not be associated with symptoms of hormone overproduction. Treatment is required for control of tumor growth and for relief of symptoms associated with excess hormone. With advances in the nonsurgical management of many hormone-related symptoms (e.g., proton pump inhibitors or somatostatin analogues), care for many of these patients has shifted toward the control of tumor progression. Complete surgical resection is the only curative treatment for these tumors. With improvements in the preoperative imaging and intraoperative localization techniques, it is hoped that these tumors will be identified and resected for cure with increased frequency. For patients with hepatic metastasis, initial expectant observation and medical management of symptoms is appropriate in view of the long and indolent course of the disease. Hepatic arterial embolization is the preferred mode of palliation for pain and hormonal symptoms. A curative hepatic resection may be possible in selected patients.

Necrolytic migratory erythema, first symptom of a malignant glucagonoma: treatment by long-acting somatostatin and surgical resection. Report of three cases

We report three cases of malignant glucagonoma with necrolytic migratory erythema as the first clinical symptom. Long-acting somatostatin analogue was the first step of a multimodal therapeutic strategy which included surgical resection of the primary tumour in every case. Liver metastases which were present in two patients were treated by hepatic arterial chemoembolization and systemic chemotherapy in one case and by liver resection for cytoreduction and hepatic arterial chemoembolization in another case. Skin lesions resolved in all three patients.

Octreotide does not prevent diarrhea in patients treated with weekly 5-fluorouracil plus high-dose leucovorin

The somatostatin analog, octreotide, is effective in treating diarrhea associated with cancer chemotherapy. This study was undertaken to determine whether octreotide could be used as prophylaxis against chemotherapy-induced diarrhea and, thereby, permit increased dose intensity. Adult cancer patients were treated with a standard regimen of intravenous 5-fluorouracil (5-FU) (600 mg/m2) plus leucovorin (LV) (500 mg/m2) weekly x 6 weeks. In addition, 150 microg of octreotide was administered subcutaneously twice daily, beginning on the first day of chemotherapy and continuing for 43 days. Escalation of 5-FU was planned for successive cohorts based upon toxicity. Eleven patients were treated at the initial 5-FU dose level. In 10 evaluable patients, dose-limiting toxicities were diarrhea (two patients), fatigue (one patient), and hyperbilirubinemia (one patient). Diarrhea was experienced by six of 10 patients, and only three patients were able to receive six weekly chemotherapy treatments without dose reduction or delay. At a dose of 150 microg twice daily, octreotide did not prevent diarrhea associated with 5-FU plus LV, and 5-FU dose escalation was not possible. While octreotide is successful in the treatment of 5-FU-induced diarrhea, we were unable to demonstrate a role in toxicity prophylaxis.

Islet cell tumors of the pancreas

Pancreatic endocrine neoplasms are a heterogeneous group of tumors that produce active hormones and result in distinct clinical syndromes. For the most part, they are malignant and require sophisticated diagnostic and localization techniques in order to identify their presence. Delays in diagnosis are the rule rather than the exception. Improvements in the diagnosis of gastrinomas and insulinomas appear to result in an increase in resectability rates. The widespread availability of intraoperative ultrasonography, as well as improved knowledge of the location of these tumors, has also had an impact on improved cure rates. With heightened awareness of these syndromes, increasing numbers of patients can be identified and more effective treatments developed for the refractory and recurrent tumors.

Octreotide in the treatment of diarrhoea induced by coeliac plexus block

Prolonged and severe diarrhoea after alcohol celiac plexus block is a rare, but life-threatening, complication if not recognized. This type of diarrhoea may be considered an autonomic neuropathy due to sympathetic denervation. A 65-year-old pancreatic cancer patient developed serious diarrhoea after celiac plexus block which was unresponsive to traditional treatment such as loperamide, dyphenoxylate and opioids. Subcutaneous octreotide, 0.1 mg twice a day, achieved a complete resolution of the symptom. This drug was maintained at the same dosage and was well tolerated for 4 months until death. Octreotide, an analogue of somatostatin, reduces diarrhoea by suppression of intestinal motility and secretion and offers a useful option in the treatment of this complication of celiac plexus block.

Evaluation of the long-acting somatostatin analogue octreotide in the management of insulinoma in three dogs

The response of dogs with insulinoma to surgical and medical management is variable, with the majority developing intractable hypoglycaemia. A long-acting somatostatin analogue, Octreotide (SMS 201-995; Sandostatin) has been useful in the management of hypoglycaemia in humans with insulinoma, and preliminary reports suggest a beneficial clinical response in dogs with insulinoma. The present study objectively evaluated Octreotide in the management of three dogs with immunohistochemically confirmed insulinoma. Octreotide had no benefit over placebo, and little effect on circulating glucose and insulin concentrations despite clearly detectable plasma concentrations of Octreotide. No clinical improvement was apparent in two dogs given Octreotide over a period of two and three weeks. These results contrast with the positive clinical responses noted previously and indicate that further placebo controlled, objective studies are necessary before clear statements on the treatment of insulinoma with Octreotide are made.

Overview: the management of metastatic carcinoid tumors

Chemotherapy, IFN, octreotide, and hepatic artery embolization can be useful for palliation, both of local symptoms and of the carcinoid syndrome, but they have little effect on tumor progression, MIBG therapy is still experimental but may have a future role. OLT should be considered as a palliative procedure in those patients with severe symptoms and no evidence of extrahepatic disease.

The role of octreotide in palliative care

Octreotide, an analogue of somatostatin with a more favorable pharmacokinetic profile, is a new drug that may offer some advantages in the palliative care setting. It has been used with favorable results in the management of some gastrointestinal disorders, such as gastrointestinal hemorrhage, diarrhea, short-bowel syndrome, fistula, and intestinal occlusion in the palliative care setting. These favorable results occurred without important side effects, underlining the potential role of this drug. The cost-benefit ratio of this expensive drug must be considered, however.

Clinical use of the long acting somatostatin analogue octreotide in pediatrics

Preliminary data of the use of the long-acting somatostatin analog octreotide (Sandostatin) in pediatrics are reported. In nesidioblastosis and other hyperinsulinemic conditions, timely treatment with octreotide can protect cerebral function and may reduce mortality. The acute use of octreotide produces prompt elevation of blood glucose, even in patients who fail to respond to diazoxide. In addition, it may be possible to avoid the need for partial or subtotal pancreatectomy by the long-term use of octreotide. As in adults, octreotide should find a place in the symptomatic treatment of secretory diarrhea, notably the watery diarrhea hypokalemia-achlorhydria complex and pancreatic cholera syndrome. Octreotide has been shown to be effective in the treatment of familial tall stature by reducing height velocity and final height. Responses to octreotide therapy vary and the individual responsiveness must be extensively studied.

Bowel rest, intravenous hydration, and continuous high-dose infusion of octreotide acetate for the treatment of chemotherapy-induced diarrhea in patients with colorectal carcinoma

BACKGROUND

A prospective trial was conducted involving 16 patients with colorectal adenocarcinoma using a regimen of continuous-infusion octreotide acetate (Sandostatin [octreotide acetate], Sandoz, East Hanover, NJ for the treatment of severe diarrhea induced by the weekly schedule of 5-fluorouracil (5-FU) in combination with leucovorin who were refractory to opiate therapy.

METHODS

Fifteen patients had tissue-documented metastatic colorectal adenocarcinoma. An additional patient was treated adjuvantly. Fifteen patients were treated with chemotherapy consisting of 5-FU and high-dose leucovorin. The octreotide acetate regimen used was a continuous infusion of 50 micrograms/h for 12 hours followed by 100 micrograms/h for 12 hours and subsequently 150 micrograms/h for 72 hours. All patients were previous failures of diphenoxylate atropine (Lomotil diphenoxalate], Searle, Chicago, IL) given 2.5 mg orally after each loose bowel movement, but no more than 20 mg in a 24-hour period. Opiate therapy was not continued beyond 48 hours. All patients also were treated with bowel rest (nothing by mouth) and intravenous fluid hydration as well as octreotide acetate.

RESULTS

Complete resolution of diarrhea was seen in 15 of 16 patients (94%). In 4 patients this was accomplished during the 100 micrograms/h infusion, and in 11 patients during the 150 micrograms/h infusion. Recurrence of diarrhea was seen in two patients after a complete cycle of octreotide acetate. Both patients were restarted at 150 micrograms/h for 72 hours of octreotide acetate with resolution of the diarrhea within 36 hours of the infusion. No toxicity related to octreotide acetate was seen in this trial.

CONCLUSION

The continuous-infusion regimen of octreotide acetate 150 micrograms/h is an effective and safe schedule for the treatment of chemotherapy-induced diarrhea together with bowel rest and intravenous fluid hydration in a group of patients in whom the majority were treated with the weekly schedule of 5-FU and high-dose leucovorin.

Effect of a somatostatin analogue (SMS 201-995) on antral gastrin cell hyperplasia and hypergastrinemia induced by a histamine H2-receptor antagonist

The effect of a somatostatin analogue, SMS 201-995 (SMS), on antral gastrin cell hyperplasia (AGH) and hypergastrinemia associated with 14-day administration of the histamine H2-receptor antagonist (H2-RA) famotidine was studied in rats. When the famotidine group was compared with the control group, the antral gastrin cell (G-cell) number was significantly increased (P < 0.01) by approximately twofold, and the serum gastrin level was significantly increased (P < 0.01) by approximately sixfold. When the famotidine+SMS group was compared with the famotidine group, the G-cell number was significantly decreased (P < 0.01) by approximately 30%, and the serum gastrin level was significantly decreased (P < 0.01) by approximately 40%. These findings suggest that SMS may be useful for inhibiting AGH and hypergastrinemia induced by long-term H2-RA administration.

Effects of the new somatostatin analogue (BIM 23014) on blood glucose homeostasis in normal men

Changes in blood glucose homeostasis induced by the new somatostatin analogue BIM 23014 (BIM) were studied. Eight normal men (study 1) received either vehicle or 1000, 2000 and 3000 micrograms BIM as a 24 h s.c. infusion. Blood glucose, plasma insulin, C-peptide, glucagon and growth hormone (GH) were measured before treatment and then hourly for 24 h. In five normal men (study 2) an oral glucose tolerance test (OGTT) was performed during vehicle infusion and then on days 1 and 7 of a continuous s.c. infusion of 2000 micrograms BIM daily for 7 days. The same biological parameters as in study 1 were measured before OGTT and then twice-hourly for 5 h. Dose-dependent and transient glucose intolerance was observed in the first half of study 1. Except for glucagon, BIM significantly (P < 0.01) reduced plasma insulin, C-peptide and GH levels. In study 2 BIM infusion induced glucose intolerance and a drop in plasma insulin and C-peptide on day 1 which disappeared on day 7 of infusion. Higher on day 7 than on day 1, plasma GH secretion was significantly (P < 0.01) reduced throughout BIM infusion. In contrast plasma glucagon levels were not modified at any time. Side-effects were abdominal cramps and diarrhoea which were observed in most subjects when increasing BIM daily dose. In conclusion, BIM infusion induced transient changes in glucose homeostasis and insulin secretion in normal men. By contrast, plasma GH levels remained reduced throughout the treatment. BIM appears to be a useful tool to selectively inhibit GH secretion.

Reduction of the effluent volume in high-output ileostomy patients by a somatostatin analogue, SMS 201-995

Twelve ileostomy patients were given subcutaneous SMS 201-995 therapy (100 micrograms t.d.s. for 5 days) in a randomized placebo-controlled trial. All patients had ileostomies constructed 60 cm proximal to the terminal ileum (proximal ileostomy) following restorative proctocolectomy. SMS 201-995 reduced the daily ileostomy output from 997 +/- 52 g to 736 +/- 28 g, P < 0.05, along with a decrease in daily sodium and chloride excretion (sodium: 92.60 +/- 8.51 to 75.22 +/- 8.64 mEq, chloride: 143.46 +/- 8.54 to 113.60 +/- 15.84 mEq; both P < 0.05). There were no significant changes in the plasma levels of glucagon, C peptide, insulin, renin or aldosterone with SMS 201-995 therapy. Patients developed no severe side effects and reported easier management of the ileostomy and a reduction in thirst. Our results suggest a possible clinical role for SMS 201-995 in the management of proximal ileostomy.

Secretory diarrhea in villous adenoma of rectum: effect of treatment with somatostatin and indomethacin

The effects of treatment with the synthetic long-acting somatostatin analogue SMS-201-995 were studied in a patient with a fluid and electrolyte secreting villous adenoma of the rectum. The effects of SMS-201-995 on rectal fluid volume and electrolyte loss, and local and general prostanoid production were compared with those of treatment with indomethacin. During treatment with the somatostatin analogue iso-osmolar rectal fluid production increased about 25%; the quantity of prostaglandin E2 in the rectal fluid rose almost 20-fold. Prostaglandin F2 alpha, 6-keto-prostaglandin F1 alpha and 13,14-dihydro-15-keto-prostaglandin F2 alpha output showed similar, though less impressive increments during somatostatin treatment. The somatostatin analogue did not affect urinary prostanoid excretion except for levels of 2,3-dinor-thromboxane B2, which doubled. With indomethacin treatment diurnal rectal fluid production dropped by about 50% and all prostanoids measured in urine and rectal fluid decreased below control values. It appears that the somatostatin analogue SMS-201-995 has a marked stimulatory effect on the in vivo prostanoid production by the villous adenoma. Perhaps this stimulation is not confined to the tumor only, but also affects thromboxane synthesis.

Diabetic diarrhea. An underdiagnosed complication?

Diarrhea is a common gastrointestinal problem in diabetes, and its prevalence has been underestimated. The cause of diabetic diarrhea is unknown, but it is probably related to gastrointestinal motility disturbances secondary to diabetic autonomic neuropathy. Other causes (especially primary malabsorption syndromes and islet cell tumors) must be excluded. Treatment of diabetic diarrhea is largely symptomatic and only moderately effective. Antidiarrheal agents may ameliorate acute episodes. Broad-spectrum antibiotics and clonidine hydrochloride (Catapres) have had some success in long-term control. Most recently, subcutaneous administration of somatostatin analogues has been shown to be helpful, the main side effects being drowsiness and vomiting.

The therapeutic role of octreotide in the management of surgical disorders

The long-acting somatostatin analogue, octreotide, has recently been made available for clinical use in the United States. This novel synthetic peptide possesses a broad spectrum of physiologic actions primarily involving the inhibition of a variety of gastrointestinal and endocrine functions. Such actions have been utilized in the management of a variety of surgical disorders. Current understanding of the indications and efficacy of this agent in the treatment of surgical disease is reviewed.

Nutritional support of patients with AIDS

Investigators are now predicting that nearly 100% of the estimated 12 million HIV-positive persons in the world will develop AIDS. Most persons with AIDS will experience progressive weight loss and malnutrition prior to death. Because nutritional therapy clearly has a beneficial effect on the clinical course and immunologic status of the critically ill general population, one must not disregard its potential for benefits in the treatment of persons with AIDS. As a result of the escalating cost of medical therapy and the inevitable AIDS epidemic, the nutritional management of persons with AIDS must be simple to administer and cost effective. The author has developed nutritional screening criteria to identify those patients who would most benefit from nutritional therapy. Because these patients differ in their nutritional requirements, diet tolerance, and degree of gut dysfunction, there is no single nutritional therapy that can be used routinely to treat all malnourished persons with AIDS.

Pilot study of sandostatin (octreotide) therapy of refractory HIV-associated diarrhea

Seventeen AIDS patients were enrolled in a prospective open-label dose-finding study of octreotide (Sandostatin) therapy for refractory diarrhea. Five were nonevaluable due to progression of AIDS symptomatology, and one was excluded because of lack of confirmation of HIV infection. Five of 11 evaluable patients responded to therapy (45%); two each at 50 micrograms and 100 micrograms, and one at 250 micrograms thrice daily doses. A sixth patient demonstrated a moderate reduction in stool volume at 250 micrograms thrice daily, which, although deemed clinically relevant, did not meet the criteria for response. On discontinuation of therapy, diarrhea recurred in all patients within 1-12 days, and responded to reinitiation of octreotide in those five patients who resumed treatment. Only one of the three patients with concurrent cryptosporidial infection responded to treatment. The drug was well tolerated, with mild symptomatology in three patients. Long-term treatment at a stable dose was effective in three of five treated patients for periods for seven months in one (moderate responder) and one year in two. One patient required dose increases to control symptoms, but after one year of treatment developed severe nausea following injections, which required dose cessation. One patient had partial control of his diarrhea for only three months despite two dose increases. These data suggest that octreotide may be of useful therapeutic value in HIV-associated diarrhea and that further studies are indicated.

Diarrhoea--an unrecognised hazard of coeliac plexus block

Coeliac plexus block is a safe procedure with relatively few side-effects. We report two cases of persistent severe diarrhoea following coeliac plexus block and explore the possible reasons for this previously unrecognised side-effect. We postulate that somatostatin analogue may be useful as treatment for diarrhoea following neurolytic coeliac plexus block that is unresponsive to conventional anti-diarrhoeal agents.

Severe posthemicolectomy diarrhea: evaluation and treatment with SMS 201-995

The effect of subcutaneous somatostatin analogue SMS 201-995 (Sandoz Pharmaceuticals Corp., East Hanover, NJ) was investigated in a patient with acute postoperative secretory diarrhea. The patient was hospitalized with bowel obstruction caused by a descending colon adenocarcinoma. One week after left hemicolectomy and transverse colostomy, watery colostomy output, which exceeded 10 L per day developed. Jejunal perfusion studies suggested that the patient's diarrhea was caused by abnormal net secretion of water and electrolytes by the small intestine. Circulating levels of various peptide hormones were normal with the exception of elevated level of pancreatic polypeptide. SMS 201-995 administration reduced colostomy output and normalized many of the abnormalities found during jejunal perfusion. These results indicate that the patient's acute secretory diarrhea, occurring after large intestinal obstruction, originated in the small intestine and that SMS 201-995 can be used to manage this unusual severe postoperative problem.

Effect of somatostatin analogs on gastric acid secretion in dogs and rats

The effects of several superactive analogs of somatostatin on gastric acid response to various exogenous and endogenous stimulants were investigated in conscious dogs and rats with gastric fistulae (GF). The inhibition was compared to that induced by somatostatin-14 (S-S-14) at two dose levels. Several octapeptide analogs of somatostatin including D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH2 (RC-160) and D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH2 (RC-121), which were superactive in tests on suppression of GH levels, were 4-5 times more potent than S-S-14 in inhibiting desglugastrin-stimulated gastric acid secretion in GF dogs. The analog RC-160 also reduced the rise in serum gastrin levels and gastric acid secretion induced by sham feeding (SF) in dogs with gastric and esophageal fistulae (EF), but did not decrease food consumption. Gastric acid secretion induced by histamine (80 micrograms/kg/h) in dogs was not affected by 1-5 micrograms/kg/h of analog RC-121 or by 5 micrograms/kg/h of S-S-14. Analogs RC-160, RC-121, and RC-98-I (D-Trp-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH2) and others also powerfully inhibited desglugastrin-induced potent as S-S-14 in dogs but its activity was higher in rats. The results indicate that octapeptide analogs which are superactive in GH-inhibition tests are also more potent than S-S-14 in suppressing gastric acid secretion. These findings may be of clinical value.

The use of somatostatin analog in gastroenteropancreatic tumors other than carcinoid

We have used the gastrinoma syndrome to examine the effects of SMS. Acutely, SMS decreased acid secretion and restored the BAO/MAO to normal in eight of eight patients. Basal and secretin-stimulated gastrin responses were suppressed but not normalized. Treatment for up to 2 years with SMS controlled symptoms, suppressed serum gastrin, and suppressed acid secretion. Treatment for 1 year or longer decreased tumor secretion of gastrin and diminished basal acid secretion, an effect that persisted for 48 hours after withdrawal of SMS. SMS treatment arrested progression of tumor growth only in patients in whom there was a reduction in gastrin and gastric acid secretion. In patients with metastatic disease who had high levels of gastrin, SMS treatment for 5 to 24 months did not inhibit tumor growth or decrease gastrin levels. In those patients in whom a reduction in the blood flow to liver tumors was shown angiographically, there was a progressive improvement in hormone secretion and in tumor size in the ensuing year of treatment, suggesting that a major target of SMS is that vascular supply of the tumors. Tumors shown to produce peptides other than gastrin, for example ACTH, were found to be markedly resistant to the action of SMS and continued to grow in an unbridled manner.

The clinical use of somatostatin analogues in the treatment of cancer

Somatostatin is a regulatory hormone or tissue factor which plays an inhibitory role in the normal regulation of several organ systems, including the central nervous system, hypothalamus and pituitary gland, the gastrointestinal tract and the exocrine and endocrine pancreas. Sandostatin is an analogue of somatostatin which has characteristics which makes it a better compound for clinical use than native somatostatin: it inhibits GH preferentially over insulin. It has a long half-life in the circulation, causing a prolonged inhibitory effect in somatostatin-responsive target organs. It is active after subcutaneous administration and rebound hypersecretion does not occur. Sandostatin is very well tolerated by most patients. Somatostatin receptors remain present on a variety of tumours which arise in tissues that contain these receptors normally. High numbers of somatostatin receptors have been found on GH-secreting pituitary tumours and on most metastatic endocrine pancreatic tumours and carcinoids. Sandostatin treatment ameliorates clinical symptoms in most acromegalic patients while GH hypersecretion and elevated concentrations of circulating IGF-I are well controlled. In most patients hormonal hypersecretion from endocrine pancreatic tumours and carcinoids is also suppressed during Sandostatin therapy. This results in an instant improvement in the quality of life. There is preliminary evidence of control of tumour growth. The presence of high numbers of somatostatin receptors on tumours enables in vivo receptor-imaging, with 123iodine coupled to a somatostatin analogue. This newly developed technique provides for the first time the possibility of localization of the primary tumours and their metastases and a prediction of which patients may respond to treatment with Sandostatin. Theoretically this somatostatin-receptor imaging technique represents a new approach which may be extended to other receptor-containing tumours. Therefore it may provide a new, powerful alternative to tumour localization performed with monoclonal antibody technology. Another potential development is the use of beta-emitting isotopes coupled to somatostatin analogues for therapeutic irradiation. Somatostatin analogues exert potent inhibitory effects on the growth of a variety of experimental tumour models in animals. Several mechanisms of action have been proposed including the direct antiproliferative effects of somatostatin and its analogues in a variety of tumour cell cultures. Most well-differentiated human brain tumours like meningiomas and low-grade astrocytomas contain somatostatin receptors, while undifferentiated brain tumours mainly contain EGF receptors. Fifteen percent of human breast carcinomas contain somatostatin receptors; those which do have a better prognosis. It can be concluded that somatostatin is an endogenous, naturally occurring inhibitory growth factor.(ABSTRACT TRUNCATED AT 400 WORDS)

Current diagnosis and management of Zollinger-Ellison syndrome

The treatment of patients with Zollinger-Ellison syndrome (ZES) has undergone dramatic evolution during the past decade. Although initially regarded as an incurable tumor, resection of gastrinoma for potential cure has been reported in 30% to 40% of selected patients in recent series. Conversely, although definitive control of acid hypersecretion is achieved by total gastrectomy, histamine (H2)-receptor antagonists and the newly introduced agents omeprazole and somatostatin analogues allow effective medical therapy of gastric acid overproduction. Confirmation of the diagnosis is best achieved with the I.V. secretin stimulation test, and tumor localization techniques are mandatory to identify candidates for operative tumor resection. Intraoperative sonography and careful exploration are required for tumor removal; successful tumor resection is associated with prolonged survival. The majority of patients (60%) are still found to have malignant disease at the time of diagnosis, but 10-year overall survival commonly exceeds 40%. The presence of multiple endocrine neoplasia type I (MEN-I) is seen in 10% to 25% of patients; correction of hypercalcemia alone may have therapeutic benefit in some ZES patients, and while gastrinoma resection is rarely possible, MEN-I patients demonstrate prolonged survival. The choice of medical rather than surgical therapy for acid hypersecretion depends on the suitability of each patient for careful and repeated endoscopic and chemical studies, versus the likelihood of a successful postoperative outcome. Socioeconomic, geographic, and related medical factors in each case may dictate the form of long-term antisecretory therapy. Exploration for possible tumor resection is indicated for virtually all patients who have no documented metastatic disease.

Octreotide. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in conditions associated with excessive peptide secretion

Octreotide is an analogue of somatostatin. Like endogenous somatostatin, it exerts a potent inhibitory effect on the release of anterior pituitary growth hormone and thyroid-stimulating hormone, and peptides of the gastroenteropancreatic endocrine system, while overcoming some of the shortcomings of exogenously administered somatostatin, namely a short duration of action, a need for intravenous administration and postinfusion rebound hypersecretion of hormone. Clinical studies have shown that octreotide is effective in the treatment of acromegaly and thyrotrophinomas. In comparative trials octreotide was significantly superior to bromocriptine in patients with acromegaly. Octreotide also appears to provide a significant advantage over existing therapies in the management of the carcinoid syndrome and offers considerable therapeutic potential in reversing carcinoid crises which may be life-threatening. Trials in patients with tumours producing vasoactive intestinal peptide demonstrated that octreotide may be an effective first-line choice for this condition, which has usually metastasised and become refractory to traditional symptomatic therapy. In limited studies in patients with high-output secretory diarrhoea, including cryptosporidium-related diarrhoea associated with AIDS and in patients with small bowel fistulas, octreotide has been shown to be effective in reducing stool/fistula output. However, well-designed clinical trials are still required to confirm its long term usefulness in these disorders. Similarly, although the use of octreotide in other conditions such as neonatal hypoglycaemia caused by nesidioblastosis, reactive pancreatitis, insulin-dependent diabetes mellitus, postprandial hypotension and the dumping syndrome has provided encouraging preliminary results, more studies are needed to clarify the place of octreotide in their treatment. Overall, octreotide appears to be well tolerated with the most frequently reported reactions being pain at the site of injection and gastrointestinal symptoms such as abdominal cramps, nausea, bloating, flatulence, diarrhoea and steatorrhoea. These adverse effects usually abate with time. Additionally, octreotide, like endogenous somatostatin, may also result in cholelithiasis, presumably by altering fat absorption and possibly by decreasing motility of the gallbladder. Thus, octreotide represents a new departure from traditional therapies in the treatment of various pathophysiological states associated with excessive peptide production and secretion. It offers a significant advantage over existing therapies in the medical management of patients with acromegaly, thyrotrophinomas, the carcinoid syndrome, tumours producing vasoactive intestinal peptide and severe secretory diarrhoea in whom conventional management options have either become exhausted or have provided suboptimal symptomatic relief.

Effect of somatostatin analog (SMS 201-995) on in vivo intestinal fluid transport in rats. A limited systemic effect

Somatostatin analog, SMS 201-995, effectively inhibits the release of hormones from gastrointestinal endocrine tumors and reduces hormonally mediated diarrheas. Its clinical efficacy in nonhormonally mediated diarrhea is limited, despite a potent antisecretory and proabsorptive effect in vitro. The effect of serosal addition of SMS 201-995 on in vitro short-circuit current responses in rat intestine is dependent upon chloride and more marked in colon and ileum than jejunum. In contrast, in vivo loop studies demonstrated that systemic administration of SMS 201-995 for five consecutive days produced a paradoxical decrease in basal colonic fluid absorption with no effect in jejunum or ileum. Furthermore, systemically administered SMS 201-995 did not alter cholera toxin-stimulated intestinal secretion. We conclude that despite a previously identified intestinal antisecretory and proabsorptive effect of SMS 201-995 in vitro, this effect is not seen in vivo and may explain the limited use of SMS 201-995 as an antidiarrhoeal agent in nonhormonally mediated diarrhoea.

Use of long-acting somatostatin analog SMS 201-995 in patients with pancreatic islet cell tumors

Natural somatostatin reduces plasma concentrations of many peptides, and is of short term benefit in patients with islet cell tumors, but has to be given as a continuous intravenous infusion. We review the published experience with the long acting synthetic somatostatin analogue SMS 201-995 in patients with islet cell tumors. Fifteen of 18 patients with vasoactive intestinal peptide-producing tumors, 8 of 8 patients with glucagonomas, 7 of 7 patients with unresectable insulinomas, and 3 of 3 patients with growth hormone releasing factor-producing tumors had a good sustained symptomatic response to SMS 201-995. Patients with benign insulinomas responded variably and are best treated by surgery. Patients with gastrinomas are best treated by oral gastric antisecretory agents. In all these syndromes, the clinical response to SMS 201-995 did not necessarily parallel the change in plasma concentration of marker peptide, suggesting that SMS 201-995 may have actions at various sites. The effect of SMS 201-995 on tumor size has been assessed in 46 patients, less than 20% of whom showed a reduction in tumor size. Side effects have been mild, but include steatorrhea and gastrointestinal disturbances. More studies will be required to fully assess the effects of long-term administration of SMS 201-995.

Use of somatostatin analog in management of carcinoid syndrome

Carcinoid tumors are the most frequent gut neuroendocrine tumors accounting for more than 50% of all tumors of the gastroenteropancreatic (GEP) axis. These tumors appear to derive from a stem cell line capable of differentiating into a variety of malignant cells that secrete many different peptides and amines. The symptoms of carcinoid tumors are often non-specific, vague abdominal pain that may precede the diagnosis by a median of 9 years. Carcinoid syndrome occurs in less than 10% of patients. We evaluated the effects of SMS 201-995 in 14 such patients, 12 with diarrhea, 8 with flushing, 3 with wheezing, one with tricuspid valve incompetence, 6 with facial telangiectasia, 3 with a pellagra type dermatosis and one with myopathy. Diarrhea was abolished or significantly reduced in 83%, flushing in 100%, wheezing in 100%, and myopathy improved in the one patient. Blood serotonin was resistant to change, urine 5HIAA fell in 75%, and most gut neuropeptide hormones apart from somatostatin were suppressed. Tumor growth appeared to be slowed in 2/3 of cases treated for up to 4 years. The analog of somatostatin appears to be a useful addition to the therapeutic armamentarium for carcinoid tumors and the symptom complex.

Clinical features of carcinoid syndrome and the use of somatostatin analogue in its management

A review is given on the clinical features of carcinoid syndrome including symptomatology, diagnostics, biochemistry and treatment. We have reviewed the literature on current therapy of carcinoid patients with special emphasis on the use of the somatostatin analogue SMS 20-1995. In addition, we present data on the effects of SMS 201-995 on indices of a clinical, biochemical and tumor growth. Diarrhea is abolished or significantly reduced in 75% of patients, flushing improves in 100%, wheezing in 100% with a decrease in airways resistance, and in one patient myopathy has improved. Blood serotonin is notoriously resistant to intervention and urinary 5-HIAA will decrease in 75% of causes but subsequently rebounds in 38%. Tumors, in general, continue to grow, but this may be slowed or in rare cases tumor growth is arrested. In individual instances the tumor may even infarct, leading to spontaneous cure. Tumors secreting PP, ACTH and calcitonin may be particularly resistant to treatment, whereas VIP secreting tumors appear to be sensitive.

Octreotide: a synthetic analog of somatostatin

Octreotide is an investigational synthetic peptide exhibiting actions similar to those of endogenous somatostatin. It has a longer half-life than the native hormone and can be administered by subcutaneous injection. Octreotide inhibits the secretion of growth hormone and numerous regulatory peptides of the gastroenteropancreatic system. Trials evaluating the clinical utility of octreotide indicate efficacy in the management of symptoms associated with acromegaly and hypersecretory neuroendocrine tumors, and in the control of nontumoral secretory diarrheas. Octreotide therapy is well tolerated. This agent should prove useful in the symptomatic control of a number of rare hypersecretory disorders.

Vasoactive intestinal polypeptide-secreting ganglioneuromatosis affecting the entire colon and rectum

This report describes a 7-year-old boy presenting with watery diarrhea, hypokalemia, and hypochlohydria associated with vasoactive intestinal polypeptide (VIP)-secreting ganglioneuromatosis involving the entire colon and rectum. The child's symptoms resolved following proctocolectomy, and the VIP levels returned to normal. Although 55 previous children have been reported with VIP-secreting tumors, this case is the first involving the entire colon and rectum.