Therapeutic potential of octreotide in the treatment of liver metastases

Octreotide is a synthetic analogue of somatostatin that has clear inhibitory effects on the growth of many animal and human cell lines, including colorectal cell lines both in vitro and in vivo. Colorectal cancer metastatic to the liver is clinically important, both in terms of the number of patients affected and the lack of any effective treatment for the majority of patients. Octreotide inhibits the growth of colorectal liver tumour in a number of experimental models and, in at least three tumour types, inhibits the growth of established micro-metastases. The precise mechanism of action is not known. However, the drug is likely to be most beneficial in the treatment of liver metastases when the tumour burden is relatively small. The available evidence, although experimental, suggests that octreotide may also have a beneficial effect on the development of liver metastases when used as an adjuvant to surgery in colorectal cancer and this area warrants urgent clinical investigation. The cytotoxics which are currently used as an adjuvant to surgery for colorectal cancer have unpleasant side effects which can be life-threatening. There will also be a proportion of patients who have undergone a truly curative resection of their tumour and will thus be treated unnecessarily. The potential benefits of octreotide in the adjuvant setting, although promising, remain speculative, but octreotide has an acceptably low incidence of side effects and can be administered safely for a prolonged period of time.

Is an elevated concentration of acinar cytosolic free ionised calcium the trigger for acute pancreatitis?

The pathogenesis of acute pancreatitis is poorly understood, despite well-recognised precipitating factors. Current evidence suggests that the earliest abnormalities of acute pancreatitis arise within acinar cells, but the key intracellular trigger has yet to be identified. Within the pancreas, physiological concentrations of secretagogues bind to G-protein-linked cell-surface receptors on acinar cells, evoking short, oscillatory spikes of acinar cytosolic-free ionised calcium ([Ca2+]i), an ubiquitous intracellular messenger. Specific effects within acinar cells include initiation of enzyme release through the phosphorylation cascades of stimulus-secretion coupling. Low resting levels of [Ca2+]i are restored by Ca(2+)-ATPase, which pumps calcium into the endoplasmic reticulum and out of the cell. If high concentrations of [Ca2+]i persist, toxicity results, intracellular signalling is disrupted, and cell damage occurs. Sustained elevations in acinar [Ca2+]i result from exposure to high concentrations of secretagogues, high doses of which also induce acute pancreatitis. Similarly, sustained elevations of [Ca2+]i may result from ductal hypertension, alcohol, hypoxia, hypercalcaemia, hyperlipidaemia, viral infection, and various drugs--all factors known to precipitate acute pancreatitis. We suggest that these factors precipitate acute pancreatitis by causing either excessive release of acinar [Ca2+]i, or damage to the integrity of mechanisms that restore low resting levels of [Ca2+]i, and that the consequent calcium toxicity is the key trigger in the pathogenesis of acute pancreatitis.

Effect of octreotide infusion on hepatic and tumour blood flow in two experimental models of liver metastases

OBJECTIVE

To investigate the effects of octreotide infusion on hepatic and tumour blood flow in rats with experimentally induced liver tumours.

DESIGN

Blood flow was determined in tumour-bearing rats using a dual reference microsphere technique before and after intravenous infusion of octreotide.

METHODS

Tumours were induced in syngeneic rats by intraportal injection of K12-Tr and WB2054-M adenocarcinoma cells. Hepatic arterial and portal venous inflow, tumour blood flow and systemic arterial pressure were determined before and after octreotide infusion (0.05 microgram/min).

RESULTS

In rats with K12-Tr tumours there was no change in tumour blood flow, hepatic arterial flow or portal venous inflow after octreotide infusion. In contrast, in rats with WB2054-M tumours, octreotide infusion resulted in a significant reduction in the blood flow to the hepatic tumour (from 0.37 to 0.135 ml/min/g) but had no effect on hepatic artery or portal venous inflow.

CONCLUSION

The reduction in blood flow to tumours derived from WB2054-M cells could, at least in part, explain the inhibitory effect of octreotide on the growth and development of these tumours. However, octreotide had no effect on blood flow to tumours derived from K12-Tr cells, suggesting that the analogue must inhibit tumour growth by other mechanisms.

Review article: the relative effectiveness of somatostatin and octreotide therapy in pancreatic disease

Somatostatin and octreotide inhibit basal and stimulated pancreatic secretion, stimulate reticuloendothelial system activity, modulate the cytokine cascade and are cytoprotective with respect to the pancreas. These effects of somatostatin and octreotide suggest that both drugs may be useful either in the treatment of pancreatic disorders, or in preventing acute pancreatitis following procedures on the pancreas. In recent years it has become clear that somatostatin is a useful and effective therapy for severe acute pancreatitis and in preventing complications following endoscopic retrograde cholangiopancreatography (ERCP), whereas octreotide has no beneficial effect and may be deleterious in both these indications. The differences in the therapeutic efficacy of somatostatin and octreotide in acute pancreatitis and ERCP appears to be related to their differential effects on sphincter of Oddi motility--the native hormone relaxing, and the analogue increasing, its contractility. Consequently, any beneficial effects of octreotide in both acute pancreatitis and ERCP are offset by the increased contractility of the sphincter of Oddi, which results in retention of activated enzymes within the pancreas and further autodigestion of the gland. Somatostatin and octreotide are equally effective in promoting the closure of pancreatic fistulae. However, the time to closure after commencement of therapy is much more variable and longer in patients treated with subcutaneous octreotide than those receiving intravenous somatostatin, possibly as a result of fluctuations in pancreatic enzyme secretion between consecutive administrations of the hormone. Furthermore, the initial potent inhibitory effect of octreotide on pancreatic secretion is lost after 7 days of continuous subcutaneous administration. Therefore, in terms of cost-effectiveness, somatostatin would appear to be the treatment of choice for pancreatic fistulae. Octreotide markedly reduces the complication rates after elective pancreatic surgery. It remains to be established whether somatostatin is as effective as octreotide in this indication.

Octreotide inhibits the growth and development of three types of experimental liver metastases

A study was performed to assess the effects of octreotide on the growth and development of liver metastases in rats. Tumour was induced by intraportal injection of three tumorigenic cell lines (the fibrosarcoma HSN and colonic adenocarcinomas K12/Tr and WB2054M) in syngeneic rats. Octreotide treatment (2 micrograms subcutaneously for 3 or 4 weeks) was started 18 h and 1 week after tumour induction; a delay in treatment of 1 week allowed micrometastases to develop. Treatment with octreotide significantly (P < 0.001) reduced the median hepatic replacement of liver by tumour compared with that of control rats given saline (controls: HSN 76.4 per cent, K12/Tr 17.5 per cent, WB2054M 43.9 per cent; octreotide treatment delayed 18 h: HSN 2.7 per cent, K12/Tr 0.6 per cent, WB2054M 1.3 per cent; octreotide treatment delayed 1 week: HSN 9.3 per cent, K12/Tr 2.5 per cent, WB2054M 2.3 per cent). These results clearly indicate that octreotide significantly inhibits the growth and development of experimental liver metastases. Further studies are required both to delineate the mechanism of action and to investigate these effects in a clinical setting.

Octreotide, the reticuloendothelial system, and experimental liver tumour

The inhibitory effect of octreotide on the growth of liver tumour is probably mediated (at least in part) by stimulation of the hepatic reticuloendothelial system (RES) activity. This study therefore investigated the effect of octreotide on the hepatic and splenic RES (assessed by the uptake of technetium 99m labelled albumin colloid, 99mTc-AC) in normal and tumour bearing rats and in animals treated with gadolinium chloride. The effects of gadolinium chloride and octreotide alone or in combination on the growth of liver tumour were also studied. Octreotide significantly stimulates both hepatic and splenic uptake of 99mTc-AC in normal rats and tumour bearing rats. In controls, the uptake of 99mTc-AC was significantly reduced by gadolinium chloride and was not changed by octreotide. RES blockade with gadolinium chloride significantly increased (p < 0.001) tumour growth compared with controls (hepatic replacement 42%; 95% confidence intervals (CI), 27.6 to 56.4 v 16.7%, 95% CI, 11.1 to 21.3%) whereas octreotide significantly inhibited (p < 0.001) the percentage hepatic replacement by tumour (0.7%; 95% CI, 0 to 2.3 v 16.7%; 95% CI, 11.1 to 21.3). This study highlights the importance of the RES in the development of liver tumour. Furthermore, octreotide inhibited the growth of liver tumour in rats with RES blockade, albeit to a lesser degree than in normal animals. These findings suggest that octreotide inhibits the growth of hepatic tumour by mechanisms other than stimulation of RES activity.

Fluctuations in the secretion of pancreatic enzymes between consecutive doses of octreotide: implications for the management of fistulae

OBJECTIVE

To determine whether variations in pancreatic enzyme secretion between consecutive subcutaneous administrations of octreotide explain why octreotide takes longer than somatostatin to facilitate the closure of gastrointestinal fistulae.

METHODS

Pancreatic enzyme secretion was studied over a 3-day period in a patient with a catheter left in the pancreatic duct postoperatively. On days 1 and 3 the patient did not receive octreotide (control days) but on day 2 he received subcutaneous octreotide 100 micrograms every 8 h. Pancreatic juice was collected at 2-h intervals over the 3-day period.

RESULTS

On the day of octreotide treatment, the patient's pancreatic secretory volume and protein output were significantly reduced (P < 0.001, Mann-Whitney U-test) compared with the 2 control days. The pancreatic secretory volume decreased markedly after the first injection of octreotide and remained low for the duration of the treatment period. The enzyme concentration of the pancreatic juice was also markedly reduced after the first injection of octreotide. However, approximately 4h after each octreotide injection the protein concentration of the pancreatic juice began to rise progressively, peaking approximately 6h after each administration of the analogue.

CONCLUSION

Subcutaneous administration of octreotide produces a sustained decrease in the volume of pancreatic juice secreted, but enzyme secretion rises progressively between consecutive administrations of the analogue. The net effect is therefore the production of low volumes of pancreatic juice with a high enzyme concentration between consecutive injections of octreotide, which may delay the healing of the fistula tract. This may explain why longer treatment periods are required to achieve fistula closure with octreotide than with somatostatin, particularly in the case of pancreatic fistulae.

Why portal hypertensive varices bleed and bleed: a hypothesis

Continued bleeding or early rebleeding is associated with a poor prognosis in patients with variceal haemorrhage. It is not clear why bleeding stops in some patients and continues or restarts in others. It is suggested that secondary haemodynamic changes in the splanchnic circulation after a bleed may contribute to the risk of further bleeding. These changes include the effects of hypotension on portocollateral resistance, the effects of blood in the gut on splanchnic blood flow, and the effects of blood volume expansion on portal venous pressure during resuscitation. These factors, working in concert, cause a secondary rise in portal venous pressure, which may precipitate further bleeding. Treatment aimed at preventing these secondary haemodynamic changes may be beneficial. It is probable that somatostatin and octreotide could act in this way, which may explain their therapeutic efficacy.

Water-soluble phosphazene polymers for parenteral and mucosal vaccine delivery

PCPP can be used in two different ways to potentiate an immune response. The soluble form of the polymer has been found to have immunoadjuvant activity. A single subcutaneous injection of polymer/influenza dramatically increases the ELISA, neutralizing, and HI antibodies to influenza virus compared to CFA. The polymer has also succeeded in dramatically increasing the amount of ELISA antibodies to TT. The antibody response elicited was predominantly of the IgG1 isotype. PCPP has also been used to generate micron-sized hydrogel microspheres through a process of divalent ion cross-linking of the polymer strands. These microspheres can induce significantly higher anti-TT serum IgG titers after a single intranasal immunization than TT alone.

Respiratory function after injection sclerotherapy of oesophageal varices

Arterial oxygen tension (Pao2), carbon dioxide tension (PaCO2), and vital capacity were measured preoperatively and one day postoperatively in patients with chronic hepatic cirrhosis having elective oesophageal injection sclerotherapy under general anaesthesia. The results were compared with the same measurements made in patients with chronic cirrhosis anaesthetised and scheduled to have injection sclerotherapy under general anaesthesia but who, because of variceal obliteration, only had an oesophagogastroscopy. In the injected group PaO2 decreased by 9.3 (3.0) mm Hg (1.2 (0.4) kPa) (mean (SEM)) (p < 0.02) but in the controls did not change. The difference between the two groups was significant (p < 0.02). Vital capacity decreased by 0.39 (0.08) litres (BTPS) (p < 0.01) after injection sclerotherapy but in the controls did not change. Again the difference between the two groups was significant (p < 0.02). In the injected group there was a significant correlation between the change in PaO2 and the percentage change in vital capacity (r = 0.787, p < 0.01) but no such relation was seen in control subjects. These results suggest that oesophageal injection sclerotherapy is associated with a restrictive defect in respiratory function one day after the injection caused, possibly, by sclerosant embolising to the lung.

Colonic anastomosis using the valtrac biofragmentable anastomosis ring: a new and useful surgical technique in gynecologic oncology

Patients with a primary malignancy of the female genital tract may present with the majority of their disease confined to the pelvis. Not infrequently, infiltrating contiguous extension of disease may involve the rectosigmoid colon, resulting in symptoms of partial obstruction. This presentation in the patient with an epithelial ovarian malignancy may represent a patient that can be adequately cytoreduced if a segmental resection of the rectosigmoid colon is performed. Following resection, the continuity of the lower GI tract can be restored by anastomosis of the proximal and distal ends of the colon. In our institution three patients explored for large abdominal pelvic masses required segmental resection of the rectosigmoid colon. In each patient the colonic anastomosis was performed using the valtrac biofragmentable anastomosis ring (V-BAR). None of the patients experienced any intraoperative complications, and postoperatively there was no evidence of any anastomotic leaks. The average time of return of GI function was 6 days and there was no prolongation of their hospital stay. Currently, with 3 months of follow-up no patients have reported any symptoms suggestive of anastomotic stricture. Although our experience is limited, we found that this technique can be performed much faster than traditional hand-sewn or staple techniques. We submit that in the presence of uncompromised colon, the V-BAR is a safe and effective new alternative for colonic anastomosis in gynecologic oncological surgery.

Somatostatin: an alternative to sclerotherapy?

BACKGROUND

The mortality rate of bleeding from oesophageal varices (30-40%) makes it one of the most serious emergencies today. Since in 30-40% of patients varices are actively bleeding, urgent control is mandatory for preventing the patient from dying of hypovolaemic shock.

ANALYSIS OF THE DIFFERENT METHODS

Various reports have shown the efficacy of injection sclerotherapy, one session controlling bleeding in 75-80% of patients, and a second increasing the success rate to 90-95%. However, the facilities for 24-h endoscopy and the expertise are not always available in the hospital. Therefore, there is a need for an effective stop-gap therapy for controlling variceal bleeding until definitive therapy can be carried out. Comparisons of various drugs have provided conflicting results. It is not clear whether combined vasopressin and nitroglycerin is superior to injection sclerotherapy in the acute control of variceal haemorrhage. A randomized controlled trial has showed somatostatin to be as effective as injection therapy in the control of acute variceal bleeding and incidence of recurrent bleeding in the first 5 days after initiation of therapy.

CONCLUSION

Somatostatin is a safe and effective treatment for the control of acute variceal haemorrhage and for preventing early rebleeding.

Reticuloendothelial stimulation: levamisole compared

PURPOSE

Levamisole in combination with 5-fluorouracil is an effective adjuvant for the treatment of resected Dukes stage C colon cancer. Since the mechanism of action of levamisole is not known, we have investigated its effects on hepatic and splenic reticuloendothelial system (RES) activity in the rat and compared the effect of levamisole with other known RES stimulators.

METHODS

The hepatic and splenic uptake of an intravenous dose of technetium-99m-sulfur colloid has been used to measure RES activity in rats treated with levamisole, glucan, zymosan, chlormethiazole, octreotide, and saline.

RESULTS

Levamisole significantly increased the hepatic uptake of technetium-99m-sulfur colloid and is comparable in its effect to the other RES stimulators. In contrast, levamisole has no effect on splenic RES activity.

CONCLUSION

RES function is considered to be a potentially important factor in the development of liver metastases, and the stimulatory effect of levamisole on the hepatic RES may partly explain its efficacy as an adjuvant treatment in colon cancer.

Changes in liver blood flow associated with the growth of hepatic LV10 and MC28 sarcomas in rats

Abnormalities in liver blood flow are known to occur in patients and animals with overt hepatic tumour. This study investigated the changes in liver blood flow associated with the development of overt hepatic tumour in two different models. Hepatic tumour was induced by intraportal inoculation of either 300 LV10 sarcoma cells or 10(5) MC28 sarcoma cells in rats. Liver blood flow and hepatic haemodynamics were measured 3 weeks later when overt liver tumour was present. The hepatic perfusion index (HPI), the ratio of hepatic arterial to total liver blood flow, was raised and portal venous inflow reduced in rats with LV10 tumours, but not in those with MC28 lesions. Hepatic arterial flow was unchanged in LV10 tumours when the HPI was raised and neither model demonstrated arteriosystemic or portosystemic shunting. The changes in portal venous inflow were associated with a significant increase in portal and splanchnic vascular resistance. These studies suggest that liver blood flow changes in the presence of overt hepatic tumour are not related to portal venous obstruction but may be caused by a circulating splanchnic vasoconstrictor.

An in vivo 31P MRS study of patients with liver cirrhosis: progress towards a non-invasive assessment of disease severity

Fourteen patients with liver cirrhosis of differing severity participated in a one-dimensional chemical shift imaging 31P MRS study of the liver. Patients were divided into two groups according to the severity of their liver disease using Child's classification and the aminopyrine breath test (AB test). Seven normal volunteers without liver disease acted as controls. The phosphomonester (PME) peak in normal subjects was 4.77% (95% confidence interval, CI: 4.11-5.42) of total phosphorus. The PME peak was significantly elevated in both mild cirrhosis [5.80% (95% CI: 5.46-6.14), p = 0.0051, vs normal subjects] and severe cirrhosis [9.64% (95% CI: 8.71-10.57), p = 0.0002, vs normal subjects and p = 0.001, vs mild cirrhosis]. There was a significant negative linear correlation (r = 0.88, p < 0.01) of PME with the percentage dose of 14CO2 excreted over 2 h in the AB test. pH values in patients with mild cirrhosis [7.45 (95% CI: 7.35-7.55)] but not severe cirrhosis [7.36 (95% CI: 7.25-7.47)] were significantly elevated (p = 0.04) compared to normal subjects [7.29 (95% CI: 7.17-7.41)]. Comparison of the peak area of PME at TR = 0.5 s against that using TR = 5.0 s in cirrhotic liver suggested no reduction in T1 of phosphorus metabolites in cirrhosis. A relationship between the severity of liver cirrhosis and a relative increase in PME was demonstrated and this was not due to a reduction of T1. This study highlights the clinical potential of 31P MRS as a non-invasive means of assessing the severity of liver cirrhosis.

Assay of gastricsin and individual pepsins in human gastric juice

AIMS

To develop and validate an analytical procedure for the quantitation of pepsins and gastricsin in human gastric juice and to assess its potential in a controlled gastric secretory study.

METHODS

High performance ion-exchange chromatography was used to separate human pepsin 1, 3a, 3b, 3c and gastricsin from gastric juice. Computed chromatographic areas for each enzyme were quantified by relation to a known amount of a secondary standard porcine pepsin. The assay procedure was validated by recovery and analytical precision studies. Gastric secretions after pentagastrin and insulin stimulation from 10 patients with portal hypertension were used to assess the potential of the analytical procedure.

RESULTS

The assay precision varied from 1.5 to 9.0% within batch and 7.5 to 18.1% between batch, with about 100% recoveries of porcine pepsin A from human gastric juice over the assay range 0.025-0.5 mg/ml. A fourfold increase in combined pepsin and gastricsin concentration was observed following pentagastrin and insulin stimulation. The mean percentage content of pepsins 3a, 3b, 3c, and 1 in non-stimulated gastric juice were 4%, 72%, 12% and 1.4%, respectively, and did not change significantly after gastric stimulation. An approximate doubling of the percentage of gastricsin (10% to 20%) relative to the pepsins was observed, however, after both insulin and pentagastrin stimulation.

CONCLUSIONS

This procedure for quantifying individual human pepsins and gastricsin in gastric juice is simple and reliable. It may be of considerable importance in determining the mechanisms involved in the control and secretion of these digestive enzymes in man, including the effect of anti-ulcer drugs and our understanding of the pathophysiology of peptic ulcer disease.

The management of persistent or recurrent variceal bleeding after injection sclerotherapy by somatostatin

Sixteen patients with persistent (n = 11) or recurrent (n = 5) variceal bleeding after injection sclerotherapy and balloon tamponade were treated with an intravenous infusion of somatostatin 250μg/ h. Somatostatin infusion successfully controlled the bleeding in 15 of the 16 patients but one rebled after 72 h of treatment. In one patient with poor liver function (Child’s C) bleeding was not controlled by somatostatin, further injection sclerotherapy or balloon tamponade of the oesophagus. The results of this study, although uncontrolled and with a small number of patients, suggest that somatostatin is a very effective treatment for the control of post-injection sclerotherapy variceal bleeding.

A prospective randomised controlled trial comparing the efficacy of somatostatin with injection sclerotherapy in the control of bleeding oesophageal varices

Since previous reports have suggested that somatostatin may be of value in the control of acute variceal haemorrhage, we compared its efficacy with that of injection sclerotherapy in a randomised controlled clinical trial. Eighty consecutive patients with endoscopically-proven severe variceal bleeding were randomised to injection sclerotherapy (n = 41) or somatostatin (n = 39) given as a continuous infusion of 250 micrograms/h for 5 days plus daily bolus administration of 250 micrograms. The efficacy of injection sclerotherapy and somatostatin infusion in controlling haemorrhage and preventing rebleeding (censored at 5 days), mortality (censored at 28 days) and complications was compared. The aetiology of the portal hypertension and transfusion requirements was similar between the two groups, but there were more patients with severe liver disease (Child's C) in the somatostatin group. There was no significant difference between the two treatments in the initial (p = 1.0) or overall control of bleeding (p = 0.58). Furthermore, somatostatin was as effective as injection sclerotherapy in controlling bleeding in patients with severe liver disease or in those actively bleeding at the time of their endoscopy. The relative risk of rebleeding whilst receiving somatostatin compared to injection sclerotherapy was 1.39 [95% Confidence Interval (CI) 3.73; 0.52], but this was reduced to 0.98 (95% CI 0.37; 2.67) when readjusted for Child's grading, the only prognostic factor shown to be of significance. Mortality was not significantly different between the two groups of patients (p = 0.31). The relative risk of dying whilst receiving somatostatin compared to injection sclerotherapy was 1.6 (95% CI 3.93; 0.66) but was reduced to 1.03 (95% CI 0.47; 2.47) when adjusted for Child's grading, the only significant prognostic factor. Complications in the somatostatin group were minor and less frequent than after injection sclerotherapy. The results of this study indicate that somatostatin is a safe treatment, which is as effective an endoscopic injection sclerotherapy for acute variceal bleeding.

The effect of portal venous flow on the washout of a regionally injected marker substance 99mTc-methylene diphosphonate after hepatic arterial blockade with degradable starch microspheres

Patients with hepatic metastases derived from colorectal carcinoma have a poor prognosis. Regional chemotherapy, either alone, or combined with agents such as degradable starch microspheres (DSM) that reduce or abolish intrahepatic arterial flow and potentiate the delivery of cytotoxics to hepatic metastases, have not significantly improved survival. We have investigated one positive mechanism, namely the effect of portal venous washout of cytotoxics, for the poor efficacy of drugs administered either alone or in combination with DSM via the hepatic artery in the rat. Using a radiolabelled marker, 99mTc-methylene diphosphonate (MDP), to represent a cytotoxic drug, the initial studies indicated that with the hepatic artery and portal vein clamped, a volume of 0.05 ml of the marker administered via the hepatic artery resulted in the most uniform intrahepatic distribution with minimal washout into the systemic circulation (21 +/- 3.7%). When the hepatic artery was clamped, the washout of MDP was reduced from 100% (with clamps on the portal vein and hepatic artery) to 84.2 +/- 7.7%. DSM administered concomitantly with MDP, resulted in a greater reduction of the portal venous washout of the marker (63 +/- 2.4%). Administration of DSM and MDP via the hepatic artery and with the portal vein clamped further reduced the washout of the marker to (21 +/- 2.26), results similar to those observed with inflow vessel clamps. Following restoration of portal venous flow, there was a rapid washout of 53.7 +/- 7.6% of the marker into the systemic circulation. The results of this study suggest that portal venous washout of regionally delivered cytotoxics, either alone or in combination with DSM, offer an explanation for the poor efficacy of regional chemotherapy in improving the prognosis of patients with hepatic metastases.