Different response to the long-acting somatostatin analogues lanreotide and octreotide in a patient with a malignant carcinoid

From biology to clinical practice: antiproliferative effects of somatostatin analogs in neuroendocrine neoplasms

Somatostatin analogs (SSA), specifically octreotide and lanreotide, have demonstrated antiproliferative effects in patients with neuroendocrine tumors (NET), a group of rare malignancies of diverse origin and presentation. A prominent feature of NET cells is the expression of G protein-coupled receptors called somatostatin receptors (SSTR). Although these SSTR are not uniformly present in NET, they can be instrumental in the diagnosis and treatment of NET. Apart from their application in nuclear imaging and radionuclide therapy, SSA have proven invaluable in the treatment of hormonal syndromes associated with certain NET (antisecretory effects of SSA), but it took more than two decades to convincingly demonstrate the antiproliferative effects of SSA in metastatic NET with the two pivotal studies PROMID and CLARINET. The current review summarizes three decades of SSA treatment and provides an overview of the clinical trial landscape for SSA monotherapy and combination therapy, including clinical implications and quality of life aspects, as well as ongoing fields of research.

The Antiproliferative Role of Lanreotide in Controlling Growth of Neuroendocrine Tumors: A Systematic Review

BACKGROUND

Neuroendocrine tumors (NETs) are a heterogeneous group of tumors, with >50% of cases involving the gastrointestinal system or pancreas. Somatostatin analogs (SSAs) are used for treating NET-related secretory syndromes and, more recently, for their antiproliferative effects. We conducted a systematic review of published literature on the antiproliferative efficacy and safety of the SSA lanreotide Autogel in the management of NETs to gain a fuller understanding of the evidence and identify future areas of research.

METHODS

Searches were conducted in PubMed up to March 16, 2016, and in the proceedings of four congresses from 2013 to 2016.

RESULTS

Screening of 1,132 publications identified in the searches found 40 relevant publications, including 27 full-length publications and 13 congress abstracts. Twenty-four of these publications reported antiproliferative efficacy data for lanreotide Autogel. The CLARINET study showed that 120 mg lanreotide Autogel every 4 weeks improves progression-free survival (PFS) in patients with gastroenteropancreatic (GEP)-NETs, with grade 1 or grade 2 (Ki-67 <10%) disease, providing class I evidence of its antiproliferative effects. The CLARINET open-label extension study reported a median PFS of 32.8 months with lanreotide Autogel. Other smaller studies generally support CLARINET.

CONCLUSION

Current clinical evidence shows that lanreotide Autogel has good antiproliferative activity with favorable safety and tolerability in patients with GEP-NETs, suggesting it should be considered as an early first-line treatment in this population. Further studies are needed to assess the potential benefits of higher doses and the use of lanreotide Autogel in combination therapy and as maintenance therapy in the absence of disease progression following other therapies. The Oncologist 2017;22:272-285 IMPLICATIONS FOR PRACTICE: This review presents the current clinical evidence for the antiproliferative activity of lanreotide Autogel in patients with midgut or pancreatic neuroendocrine tumors (NETs) and shows its effectiveness, safety, and tolerability in these patient populations. By systematically presenting all the clinical evidence, the review adds to existing publications by discussing results in a broad range of settings. The review also indicates future directions for investigation of the use of lanreotide Autogel in NETs originating in other locations, in combination therapy, or as maintenance therapy in progressive disease.

Refractory carcinoid syndrome: a review of treatment options

Carcinoid syndrome (CSy) is a constellation of symptoms that may commonly present in patients with well differentiated neuroendocrine tumors (NETs), with somatostatin analogs (SSAs) being the first-line option for symptom management. However, symptomatic progression eventually occurs and in this scenario of a refractory CSy; several treatment options have been studied such as dose escalation of SSA, interferon and liver-directed therapies. Nevertheless, recent phase III trials have contributed to the understanding and management of this condition. We performed a comprehensive review of interventional studies examining refractory CSy to provide the evidence for current treatment options and propose a treatment sequence.

Somatostatin analogues in functioning gastroenteropancreatic neuroendocrine tumours: literature review, clinical recommendations and schedules

OBJECTIVE

Neuroendocrine tumours (NETs) represent a heterogeneous group of neoplasms, which include functioning and non-functioning forms. Somatostatin analogues (SSAs) play a key role in the management of these tumours. Herein, we aimed at reviewing the current evidence about the role of SSAs in the treatment of gastro-entero-pancreatic (GEP)-NETs.

MATERIAL AND METHODS

An extensive bibliographical search was performed in PubMed using the following keywords: gastro-entero-pancreatic neuroendocrine tumours, somatostatin analogues, octreotide, lanreotide, in order to identify all the pertinent English-written articles published between 1990 and 2015.

RESULTS

SSAs have shown to help the symptomatic and biochemical improvement of patients with NETs and to exhibit a good safety profile. Recent studies have also reported a role for SSAs in tumour growth control, although the results are less impressive and the underlying mechanisms are not fully understood.

CONCLUSIONS

SSAs are well known as a symptomatic and, to lesser extent, anti-proliferative treatment in GEP-NETs. However, some issues, including optimal dosage, benefits and adverse events of combination with other molecules, and the role of new analogues, remain to be elucidated in further randomised studies.

Inhibition of Peripheral Synthesis of Serotonin as a New Target in Neuroendocrine Tumors

: The carcinoid syndrome represents a set of signs and symptoms associated with neuroendocrine tumors (NETs) that occur primarily when metastases are developed in the liver, resulting in the worsening of quality of life. Serotonin plays a central role in the physiology of carcinoid syndrome by promoting intestinal motility. Somatostatin analogs (SSAs) have widely demonstrated their efficacy as symptomatic relievers of carcinoid syndrome, but this control is ephemeral, being reduced by approximately 50% within the first year. The exact mechanisms of resistance to SSAs are not fully understood, but it is believed that serotonin might be involved. Patients with carcinoid syndrome present with a significant increase in serotonin plasma levels and, consequently, in the soluble urinary metabolite 5-hydroxyindole acetic acid. Telotristat etiprate is a potent inhibitor of tryptophan hydroxylase, a rate-limiting enzyme in the synthesis of serotonin, that has demonstrated in the phase III TELESTAR clinical trial a significant improvement in the control of bowel movements in patients with NETs who have carcinoid syndrome and who have progressed to an SSA. Based on these results, telotristat etiprate has emerged as a potential new option in the treatment algorithm of symptomatic control of functioning NETs. However, some issues need to be clarified, such as the safety profile of the drug outside clinical trials, the benefit in quality of life, and the possible impact on tumor growth, as well as its role within sequencing or combination treatment strategies with pre-existing drugs effective in NET treatment.

IMPLICATIONS FOR PRACTICE

This article reviews the literature about carcinoid syndrome, which affects patients diagnosed with neuroendocrine tumors. Few articles have been published about this syndrome and its pathophysiology. Somatostatin analogs provide symptomatic relief; however, patients may become refractory to this strategy, usually within the first year of treatment. In this context, as an agent with an innovative mechanism of action, telotristat etiprate has demonstrated activity in a phase III trial, and findings may offer a path to an improve quality of life and prolonged survival for certain patients.

Therapeutic management of patients with gastroenteropancreatic neuroendocrine tumours

Patients with neuroendocrine tumours (NETs) are best managed in a specialist centre as part of a multidisciplinary team comprising gastroenterologists, oncologists, endocrinologists, gastrointestinal and hepatopancreaticobiliary surgeons, pathologists, nuclear medicine physicians and technicians, radiologists, specialist nurses, pharmacists, biochemists and dieticians. This should ideally be led by a clinician with experience and interest in NETs. Although the number of medical treatments and clinical trials has increased in the decade, there is still a lack of prospective randomised trials; thus, management is mainly based on limited often single-centre studies, although there are now formal guidelines based on consensus expert opinion. We have outlined the current optimal management of patients with NETs. We have reviewed therapeutic options including surgery, somatostatin analogues and other biotherapies and peptide receptor-targeted therapy. We have discussed the challenge in managing hepatic metastases including hepatic artery embolisation, ablation and orthotopic liver transplant. In addition, we have briefly reviewed the emerging therapies such as the mammalian target of rapamycin and angiogenic inhibitors and the newer somatostatin analogues.

Long-term results of treatment of malignant carcinoid syndrome with prolonged release Lanreotide (Somatuline Autogel)

BACKGROUND

Somatostatin analogues are the mainstay of therapy for malignant carcinoid syndrome. There is clear evidence that the once monthly intramuscular formulation, Octreotide LAR, controls symptoms of carcinoid syndrome, and recent data also suggests an antitumour effect. There is limited data on prolonged release Lanreotide (Somatuline Autogel, Ipsen Pharma Biotech, Signes, France) and no long-term data to date.

AIM

To present long-term results of prolonged release Lanreotide in a large cohort of patients with malignant carcinoid syndrome, assessing clinical and objective response and tolerance.

METHODS

Seventy six patients with metastatic midgut neuroendocrine tumours and carcinoid syndrome were included in this 9-year retrospective study. Clinical response was based on symptom score with radiological assessment based on RECIST (Response Evaluation Criteria In Solid Tumours).

RESULTS

Data were available in 69 patients. Ninety four percent achieved symptomatic response at first follow-up visit. Forty six percent had loss of symptomatic response, but 44% of these achieved control with an increase in dose of prolonged release Lanreotide. Overall, symptoms were well controlled throughout the study period with prolonged release Lanreotide alone in 74% of patients. Twenty six percent required additional treatment despite good initial response. Only 30% demonstrated radiological progression. Eleven patients who were switched from Octreotide LAR had return of symptomatic control. No significant adverse effects were experienced.

CONCLUSIONS

Prolonged release Lanreotide provides good symptomatic control of diarrhoea and flushing as well as tumour stability in patients with malignant carcinoid syndrome.

The diagnosis and medical management of advanced neuroendocrine tumors

Neuroendocrine tumors (NETs) constitute a heterogeneous group of neoplasms that originate from endocrine glands such as the pituitary, the parathyroids, and the (neuroendocrine) adrenal, as well as endocrine islets within glandular tissue (thyroid or pancreatic) and cells dispersed between exocrine cells, such as endocrine cells of the digestive (gastroenteropancreatic) and respiratory tracts. Conventionally, NETs may present with a wide variety of functional or nonfunctional endocrine syndromes and may be familial and have other associated tumors. Assessment of specific or general tumor markers offers high sensitivity in establishing the diagnosis and can also have prognostic significance. Imaging modalities include endoscopic ultrasonography, computed tomography and magnetic resonance imaging, and particularly, scintigraphy with somatostatin analogs and metaiodobenzylguanidine. Successful treatment of disseminated NETs requires a multimodal approach; radical tumor surgery may be curative but is rarely possible. Well-differentiated and slow-growing gastroenteropancreatic tumors should be treated with somatostatin analogs or alpha-interferon, with chemotherapy being reserved for poorly differentiated and progressive tumors. Therapy with radionuclides may be used for tumors exhibiting uptake to a diagnostic scan, either after surgery to eradicate microscopic residual disease or later if conventional treatment or biotherapy fails. Maintenance of the quality of life should be a priority, particularly because patients with disseminated disease may experience prolonged survival.

The antitumour effect of the somatostatin analogue TT-232 depends on the treatment regimen

The somatostatin analogue TT-232, containing a five residue ring structure, has a strong antitumour activity both in vitro and in vivo. This peptide has no effect on growth hormone (GH) release, but exhibits a remarkable tyrosine kinase inhibitory effect and induced apoptosis. We studied the effect of TT-232 in different routes of administration and treatment schedules on various types of mouse tumour models. The infusion treatment with inserted Alzet osmotic minipumps proved to be superior to both twice daily subcutaneous (s.c.) or intravenous (i.v.) injections in a 2 weeks period. In the case of S-180 tumour the infusion treatment resulted in 77-100% tumour growth inhibition and in 40-60% of mice long-term and tumour-free survivors. With the P-388sc tumour the infusion of TT-232 resulted in 20-40% of animals long-term and tumour-free survivors and in 76-100% tumour growth inhibition. In the very aggressive Colon-26 (C-26) and MXT, the TT-232 treatment resulted in 71-75% tumour growth inhibition and increased survival time by about 50%.

Alteration of somatostatin receptor subtype 2 gene expression in pancreatic tumor angiogenesis

AIM: To explore the difference of somatostatin receptor subtype 2 (SST2R) gene expression in pancreatic cancerous tissue and its adjacent tissue, and the relationship between the change of SST2R gene expression and pancreatic tumor angiogenesis related genes.

METHODS: The expressions of SST2R, DPC4, p53 and ras genes in cancer tissues of 40 patients with primary pancreatic cancer, and the expression of SST2R gene in its adjacent tissue were determined by immunohistochemiscal LSAB method and EnVision^TM method. Chi-square test was used to analyze the difference in expression of SST2R in pancreatic cancer tissue and its adjacent tissue, and the correlation of SST2R gene expression with the expression of p53, ras and DPC4 genes.

RESULTS: Of the tissue specimens from 40 patients with primary pancreatic cancer, 35 (87.5%) cancer tissues showed a negative expression of SST2R gene, whereas 34 (85%) a positive expression of SST2R gene in its adjacent tissues. Five (12.5%) cancer tissues and its adjacent tissues simultaneously expressed SST2R. The expression of SST2R gene was markedly higher in pancreatic tissues adjacent to cancer than in pancreatic cancer tissues (P < 0.05). The expression rates of p53, ras and DPC4 genes were 50%, 60% and 72.5%, respectively. There was a significant negative correlation of SST2R with p53 and ras genes (χ₁² = 9.33, χ₂² = 15.43, P < 0.01), but no significant correlation with DPC4 gene (χ² = 2.08, P > 0.05).

CONCLUSION: There was a significant difference of SST2R gene expression in pancreatic cancer tissues and its adjacent tissues, which might be one cause for the different therapeutic effects of somatostatin and its analogs on pancreatic cancer patients. There were abnormal expressions of SST2R, DPC4, p53 and ras genes in pancreatic carcinogenesis, and moreover, the loss or decrease of SST2R gene expression was significantly negatively correlated with the overexpression of tumor angiogenesis correlated p53 and ras genes, suggesting that SST2R gene together with p53 and ras genes may participate in pancreatic cancerous angiogenesis.

Update on the treatment of neuroendocrine tumors

Neuroendocrine tumors represent a group of neoplasias characterized by significant histopathological and biological heterogeneity. The basic study of the biological features of neuroendocrine tumors should allow the oncologist to identify those tumor subsets more sensitive to a particular medical treatment. For example, in metastatic or advanced disease, locoregional treatments, as well as radionuclide therapies, should be suggested only in selected cases. Although it has no significant effect on tumor growth, biotherapy with somatostatin analogs and/or interferon-alpha is recommended for either well-differentiated or functioning tumors. On the other hand, chemotherapy is effective in the treatment of those tumors characterized by a poor differentiation grade and a high proliferation rate. Novel therapies, new pharmacological formulations and more selective somatostatin analogs are now under clinical investigation for the treatment of neuroendocrine tumors.