Glucagon-like peptide-1 receptor imaging for the localisation of insulinomas: a prospective multicentre imaging study

Selective Arterial Calcium Stimulation With Hepatic Venous Sampling Differentiates Insulinoma From Nesidioblastosis

CONTEXT

In adult patients with endogenous hyperinsulinemic hypoglycemia and negative or inconclusive noninvasive imaging, insulinoma and non-insulinoma pancreatogenous hypoglycemic syndrome (NIPHS) resulting from diffuse nesidioblastosis must be considered in the differential diagnosis. It is not known whether the biochemical results of selective arterial calcium stimulation (SACST) with hepatic venous sampling can differentiate insulinoma from diffuse nesidioblastosis.

OBJECTIVE

To determine the specificity of SACST with hepatic venous sampling in differentiating insulinoma from diffuse nesidioblastosis.

DESIGN

Retrospective review (January 1996 to March 2014).

SETTING

Tertiary referral center.

PATIENTS OR OTHER PARTICIPANTS

A total of 116 patients with biochemical evidence of endogenous hyperinsulinemic hypoglycemia and negative or inconclusive noninvasive imaging who were subsequently shown at surgery to have insulinoma (n = 42) or nesidioblastosis (n = 74) after undergoing SACST with hepatic venous sampling.

INTERVENTION(S)

SACST with hepatic venous sampling before pancreatic exploration.

MAIN OUTCOME MEASURE(S)

Receiver operating characteristic curves were generated from the biochemical results of SACST to determine the specificity of the maximum hepatic venous insulin concentration (mHVI) and the relative-fold increase in hepatic venous insulin concentration (rHVI) over baseline after calcium injection from the dominant artery in differentiating insulinoma from nesidioblastosis.

RESULTS

The mHVI (21.5-fold; P < .001) and rHVI (3.9-fold; P < .001) were significantly higher in the insulinoma group compared to the nesidioblastosis group. The areas under the receiver operating characteristic curve for mHVI and rHVI were excellent (0.94; P < .0001) and good (0.83; P < .0001), respectively, for differentiating insulinoma from nesidioblastosis. mHVI cutoffs of > 91.5 and > 263.5 μIU/mL were 95 and 100% specific for insulinoma, respectively. A 19-fold increase in rHVI over baseline was 99% specific for insulinoma.

CONCLUSIONS

These data suggest that the mHVI and rHVI at SACST may be useful in differentiating insulinoma from nesidioblastosis with high specificity in patients with hyperinsulinemic hypoglycemia and negative or inconclusive noninvasive imaging.

Insulinoma: a multicenter, retrospective analysis of three decades of experience (1983-2014)

OBJECTIVE

To analyze the clinical features, diagnostic procedures, treatment, and clinical outcome of insulinomas diagnosed and treated in the period 1983-2014 in four Spanish hospitals.

METHODS

All patients with either biochemical and morphological criteria of insulinoma and/or histological demonstration of insulin-secreting tumor were included.

RESULTS

Twenty-nine patients [23 women (79.3%); mean age 48.7±17.4 years (range, 16-74)] were recruited. Twenty-six patients (89.7%) had sporadic tumors, and the rest (3 women, 10.3%) developed in the context of multiple endocrine neoplasia type 1. There were 3 (10.3%) multiple insulinomas, one associated with multiple endocrine neoplasia type 1, and two (6.9%) malignant insulinomas, both sporadic. Most patients (n=18, 62.1%) had fasting hypoglycemia, about a third (31%) both postprandial and fasting hypoglycemia, and 6.9% postprandial hypoglycemia only. Time to glucose nadir (37.3±6.5mg/dL) in the fasting test was 9.0±4.4h, with maximal insulin levels of 25.0±20.3μU/mL. Abdominal CT detected insulinoma in 75% of patients. Twenty-seven (93.1%) patients underwent surgery [enucleation, 18 (66.7%) and subtotal pancreatectomy, 9 (33.3%); tumor size, 1,7±0,7cm]. Surgery achieved cure in the majority (n=24, 88.9%) of patients.

CONCLUSION

In our setting, insulinoma is usually a benign, small, and solitary tumor, mainly affecting women aged 45-50 years, and usually localized with abdominal CT. The most commonly used surgical technique is enucleation, which achieves a high cure rate.

Preoperative Glucagon-like peptide-1 receptor imaging reduces surgical trauma and pancreatic tissue loss in insulinoma patients: a report of three cases

Background

Insulinomas are rare tumors, in the majority of cases best treated by surgical resection. Preoperative localization of insulinoma is challenging. The more precise the preoperative localization the less invasive and safer is the resection. The purpose of the study is to check the impact of a new technique to localize insulinoma on the surgical strategy.

Findings

We present exact preoperative localization with Glucagon-like peptide-1 receptor (GLP-1R) imaging. This allows a more precise resection thereby reducing surgical access trauma, loss of healthy pancreatic tissue and increasing safety and quality of the surgical intervention.

Conclusion

With the help of precise preoperative localization of insulinoma with GLP-1R imaging the surgeon is able to minimize the amount of resected healthy pancreatic tissue. We hypothesize that GLP-1R imaging will become a preoperative diagnostic tool to be used for many patients scheduled for open or laparoscopic insulinoma resection.

Localization of Hidden Insulinomas with ⁶⁸Ga-DOTA-Exendin-4 PET/CT: A Pilot Study

(111)In-DOTA-exendin-4 SPECT/CT has been shown to be highly efficient in the detection of insulinomas. We aimed at determining whether novel PET/CT imaging with [Nle(14),Lys(40)(Ahx-DOTA-(68)Ga)NH2]exendin-4 ((68)Ga-DOTA-exendin-4) is feasible and sensitive in detecting benign insulinomas.

METHODS

(68)Ga-DOTA-exendin-4 PET/CT and (111)In-DOTA-exendin-4 SPECT/CT were performed in a randomized cross-over order on 5 patients with endogenous hyperinsulinemic hypoglycemia. The gold standard for comparison was the histologic diagnosis after surgery.

RESULTS

In 4 patients histologic diagnosis confirmed a benign insulinoma, whereas one patient refused surgery despite a positive (68)Ga-DOTA-exendin-4 PET/CT scan. In 4 of 5 patients, previously performed conventional imaging (CT or MR imaging) was not able to localize the insulinoma. (68)Ga-DOTA-exendin-4 PET/CT correctly identified the insulinoma in 4 of 4 patients, whereas (111)In-DOTA-exendin-4 SPECT/CT correctly identified the insulinoma in only 2 of 4 patients.

CONCLUSION

These preliminary data suggest that the use of (68)Ga-DOTA-exendin-4 PET/CT in detecting hidden insulinomas is feasible.

Evaluation of ¹¹¹in-labelled exendin-4 derivatives containing different meprin β-specific cleavable linkers

BACKGROUND

Cleavable linkers, which are specifically cleaved by defined conditions or enzymes, are powerful tools that can be used for various purposes. Amongst other things, they have been successfully used to deliver toxic payloads as prodrugs into target tissues. In this work novel linker sequences targeting meprin β, a metalloprotease expressed in the kidney brush-border membrane, were designed and included in the sequence of three radiolabelled exendin-4 derivatives. As radiolabelled exendin-4 derivatives strongly accumulate in the kidneys, we hypothesised that specific cleavage of the radiolabelled moiety at the kidney brush-border membrane would allow easier excretion of the activity into the urine and therefore improve the pharmacological properties of the peptide.

RESULTS

The insertion of a cleavable linker did not negatively influence the in vitro properties of the peptides. They showed a good affinity to the GLP-1 receptor expressed in CHL cells, a high internalisation and sufficiently high stability in fresh human blood plasma. In vitro digestion with recombinant meprin β rapidly metabolised the corresponding linker sequences. After 60 min the majority of the corresponding peptides were digested and at the same time the anticipated fragments were formed. The peptides were also quickly metabolised in CD1 nu/nu mouse kidney homogenates. Immunofluorescence staining of meprin β in kidney sections confirmed the expression of the protease in the kidney brush-border membrane. Biodistribution in GLP-1 receptor positive tumour-xenograft bearing mice revealed high specific uptake of the 111In-labelled tracers in receptor positive tissue. Accumulation in the kidneys, however, was still high and comparable to the lead compound 111In-Ex4NOD40.

CONCLUSION

In conclusion, we show that the concept of cleavable linkers specific for meprin β is feasible, as the peptides are rapidly cleaved by the enzyme while retaining their biological properties.

Glucagon-like-peptide-1 receptor expression in normal and diseased human thyroid and pancreas

Glucagon-like-peptide-1 (GLP1) analogs may induce thyroid or pancreatic diseases in animals, raising questions about their use in diabetic patients. There is, however, controversy regarding expression of GLP1 receptors (GLP1R) in human normal and diseased thyroid and pancreas. Here, 221 human thyroid and pancreas samples were analyzed for GLP1R immunohistochemistry and compared with quantitative in vitro GLP1R autoradiography. Neither normal nor hyperplastic human thyroids containing parafollicular C cells express GLP1R with either method. Papillary thyroid cancer do not, and medullary thyroid carcinomas rarely express GLP1R. Insulin- and somatostatin-producing cells in the normal pancreas express a high density of GLP1R, whereas acinar cells express them in low amounts. Ductal epithelial cells do not express GLP1R. All benign insulinomas express high densities of GLP1R, whereas malignant insulinomas rarely express them. All ductal pancreatic carcinomas are GLP1R negative, whereas 6/20 PanIN 1/2 and 0/12 PanIN 3 express GLP1R. Therefore, normal thyroid, including normal and hyperplastic C cells, or papillary thyroid cancer are not targets for GLP1 analogs in humans. Conversely, all pancreatic insulin- and somatostatin-producing cells are physiological GLP1 targets, as well as most acini. As normal ductal epithelial cells or PanIN 3 or ductal pancreatic carcinomas do not express GLP1R, it seems unlikely that GLP1R is related to neoplastic transformation in pancreas. GLP1R-positive medullary thyroid carcinomas and all benign insulinomas are candidates for in vivo GLP1R targeting.

Detection of insulinoma using (68)Gallium-DOTATATE PET/CT: a case report

Insulinomas are the most common cause of endogenous hyperinsulinemic hypoglycemia in non-diabetic adults. They are most often benign, small and difficult to localize with current imaging techniques. This is of high importance, as complete surgical resection is the only curative treatment. Anatomic imaging, (111)In-pentetreotide scan and (68)Gallium-DOTATATE positron emission tomography/computed tomography (PET/CT) were compared in a patient with insulinoma. (68)Gallium-DOTATATE PET/CT and selective arterial calcium stimulation localized the insulinoma. At surgery, a tumor in the anterior aspect of the pancreatic body was found which confirmed the preoperative localization, and a 2.1 cm tumor was enucleated, World Health Organization (WHO) grade I insulinoma. The patient remains euglycemic and free of symptoms at last follow up. In conclusion, (68)Gallium-DOTATATE PET/CT imaging may be a useful adjunct localizing study for insulinomas. It is a non-invasive preoperative localization study that could guide surgical exploration for successful therapy.

The rise, fall, and resurgence of immunotherapy in type 1 diabetes

Despite considerable effort to halt or delay destruction of β-cells in autoimmune type 1 diabetes (T1D), success remains elusive. Over the last decade, we have seen a proliferation of knowledge on the pathogenesis of T1D that emerged from studies performed in non-obese diabetic (NOD) mice. However, while results of these preclinical studies appeared to hold great promise and boosted patients' hopes, none of these approaches, once tested in clinical settings, induced remission of autoimmune diabetes in individuals with T1D. The primary obstacles to translation reside in the differences between the human and murine autoimmune responses and in the contribution of many environmental factors associated with the onset of disease. Moreover, inaccurate dosing as well as inappropriate timing and uncertain length of drug exposure have played a central role in the negative outcomes of such therapeutic interventions. In this review, we summarize the most important approaches tested thus far in T1D, beginning with the most successful preclinical studies in NOD mice and ending with the latest disappointing clinical trials in humans. Finally, we highlight recent stem cell-based trials, for which expectations in the scientific community and among individuals with T1D are high.

A comparison of three (67/68)Ga-labelled exendin-4 derivatives for β-cell imaging on the GLP-1 receptor: the influence of the conjugation site of NODAGA as chelator

Background

Various diseases derive from pathologically altered β-cells. Their function can be increased, leading to hyperinsulinism, or decreased, resulting in diabetes. Non-invasive imaging of the β-cell-specific glucagon-like peptide receptor-1 (GLP-1R) would allow the assessment of both β-cell mass and derived tumours, potentially improving the diagnosis of various conditions. We tested three new ^67/68Ga-labelled derivatives of exendin-4, an agonist of GLP-1R, in vitro and in vivo. We determined the influence of the chelator NODAGA conjugated to resident lysines either at positions 12 and 27 or the C-terminally attached lysine at position 40 on the binding and kinetics of the peptide.

Methods

Binding and internalisation of ⁶⁷Ga-labelled Ex4NOD12, Ex4NOD27 and Ex4NOD40 were tested on Chinese hamster lung (CHL) cells stably transfected to express the GLP-1 receptor (GLP-1R). In vivo biodistribution of ⁶⁸Ga-labelled peptides was investigated in CD1 nu/nu mice with subcutaneous CHL-GLP-1R positive tumours; the specificity of the binding to GLP-1R was determined by pre-injecting excess peptide.

Results

All peptides showed good in vitro binding affinities to GLP-1R in the range of 29 to 54 nM. ^67/68Ga-Ex4NOD40 and ^67/68Ga-Ex4NOD12 show excellent internalisation (>30%) and high specific uptake in GLP-1R positive tissue, but high activity was also found in the kidneys.

Conclusions

We show that of the three peptides, Ga-Ex4NOD40 and Ga-Ex4NOD12 demonstrate the most favourable in vitro properties and in vivo binding to GLP-1R positive tissue. Therefore, we conclude that the lysines at positions 12 and 40 might preferentially be utilised for modifying exendin-4.

In vivo imaging of GLP-1R with a targeted bimodal PET/fluorescence imaging agent

Accurate visualization and quantification of β-cell mass is critical for the improved understanding, diagnosis, and treatment of both type 1 diabetes (T1D) and insulinoma. Here, we describe the synthesis of a bimodal imaging probe (PET/fluorescence) for imaging GLP-1R expression in the pancreas and in pancreatic islet cell tumors. The conjugation of a bimodal imaging tag containing a near-infrared fluorescent dye, and the copper chelator sarcophagine to the GLP-1R targeting peptide exendin-4 provided the basis for the bimodal imaging probe. Conjugation was performed via a novel sequential one-pot synthetic procedure including (64)Cu radiolabeling and copper-catalyzed click-conjugation. The bimodal imaging agent (64)Cu-E4-Fl was synthesized in good radiochemical yield and specific activity (RCY = 36%, specific activity: 141 μCi/μg, >98% radiochemical purity). The agent showed good performance in vivo and ex vivo, visualizing small xenografts (<2 mm) with PET and pancreatic β-cell mass by phosphor autoradiography. Using the fluorescent properties of the probe, we were able to detect individual pancreatic islets, confirming specific binding to GLP-1R and surpassing the sensitivity of the radioactive label. The use of bimodal PET/fluorescent imaging probes is promising for preoperative imaging and fluorescence-assisted analysis of patient tissues. We believe that our procedure could become relevant as a protocol for the development of bimodal imaging agents.

Detection of metastatic insulinoma by positron emission tomography with [(68)ga]exendin-4-a case report

CONTEXT

Insulinomas are the most common cause of endogenous hyperinsulinemic hypoglycemia in nondiabetic adult patients. They are usually benign, and curative surgery is the "gold standard" treatment if they can be localized. Malignant insulinomas are seen in less than 10% of patients, and their prognosis is poor. The glucagon like peptide-1 receptor (GLP-1R) is markedly up-regulated in insulinomas-especially benign lesions, which are difficult to localize with current imaging techniques.

OBJECTIVE

The aim of the study was to assess the possibility of the detection of primary and metastatic insulinoma by positron emission tomography (PET) using [(68)Ga]Ga-DO3A-VS-Cys(40)-Exendin-4 ([(68)Ga]Exendin-4) in a patient with severe hypoglycemia.

DESIGN AND SETTING

Dynamic and static PET/computed tomography (CT) examination of a patient was performed using [(68)Ga]Exendin-4 at Uppsala University Hospital, Uppsala, Sweden.

PATIENTS

A patient presented with hypoglycemia requiring continuous iv glucose infusions. A pancreatic insulinoma was suspected, and an exploratory laparotomy was urgently performed. At surgery, a tumor in the pancreatic tail with an adjacent metastasis was found, and a distal pancreatic resection (plus splenectomy) and removal of lymph node were performed. Histopathology showed a World Health Organization classification grade II insulinoma. Postoperatively, hypoglycemia persisted, but a PET/CT examination using the neuroendocrine marker [(11)C]-5-hydroxy-L-tryptophan was negative.

INTERVENTIONS

The patient was administered [(68)Ga]Exendin-4 and was examined by dynamic PET over the liver and pancreas.

RESULTS

The stable GLP-1 analog Exendin-4 was labeled with (68)Ga for PET imaging of GLP-1R-expressing tumors. The patient was examined by [(68)Ga]Exendin-4-PET/CT, which confirmed several small GLP-1R-positive lesions in the liver and a lymph node that could not be conclusively identified by other imaging techniques. The results obtained from the [(68)Ga]Exendin-4-PET/CT examination provided the basis for continued systemic treatment.

CONCLUSION

The results of the [(68)Ga]Exendin-4-PET/CT examination governed the treatment strategy of this particular patient and demonstrated the potential of this technique for future management of patients with this rare but potentially fatal disease.

GEP-NETS update: functional localisation and scintigraphy in neuroendocrine tumours of the gastrointestinal tract and pancreas (GEP-NETs)

For patients with neuroendocrine tumours (NETs) of the gastrointestinal tract and pancreas (GEP) (GEP-NETs), excellent care should ideally be provided by a multidisciplinary team of skilled health care professionals. In these patients, a combination of nuclear medicine imaging and conventional radiological imaging techniques is usually mandatory for primary tumour visualisation, tumour staging and evaluation of treatment. In specific cases, as in patients with occult insulinomas, sampling procedures can provide a clue as to where to localise the insulin-hypersecreting pancreatic NETs. Recent developments in these fields have led to an increase in the detection rate of primary GEP-NETs and their metastatic deposits. Radiopharmaceuticals targeted at specific tumour cell properties and processes can be used to provide sensitive and specific whole-body imaging. Functional imaging also allows for patient selection for receptor-based therapies and prediction of the efficacy of such therapies. Positron emission tomography/computed tomography (CT) and single-photon emission CT/CT are used to map functional images with anatomical localisations. As a result, tumour imaging and tumour follow-up strategies can be optimised for every individual GEP-NET patient. In some cases, functional imaging might give indications with regard to future tumour behaviour and prognosis.

Radiolabelled GLP-1 receptor antagonist binds to GLP-1 receptor-expressing human tissues

PURPOSE

Radiolabelled glucagon-like peptide 1 (GLP-1) receptor agonists have recently been shown to successfully image benign insulinomas in patients. For the somatostatin receptor targeting of tumours, however, it was recently reported that antagonist tracers were superior to agonist tracers. The present study therefore evaluated various forms of the (125)iodinated-Bolton-Hunter (BH)-exendin(9-39) antagonist tracer for the in vitro visualization of GLP-1 receptor-expressing tissues in rats and humans and compared it with the agonist tracer (125)I-GLP-1(7-36)amide.

METHODS

Receptor autoradiography studies with (125)I-GLP-1(7-36)amide agonist or (125)I-BH-exendin(9-39) antagonist radioligands were performed in human and rat tissues.

RESULTS

The antagonist (125)I-BH-exendin(9-39) labelled at lysine 19 identifies all human and rat GLP-1 target tissues and GLP-1 receptor-expressing tumours. Binding is of high affinity and is comparable in all tested tissues in its binding properties with the agonist tracer (125)I-GLP-1(7-36)amide. For comparison, (125)I-BH-exendin(9-39) with the BH labelled at lysine 4 did identify the GLP-1 receptor in rat tissues but not in human tissues.

CONCLUSION

The GLP-1 receptor antagonist exendin(9-39) labelled with (125)I-BH at lysine 19 is an excellent GLP-1 radioligand that identifies human and rat GLP-1 receptors in normal and tumoural tissues. It may therefore be the molecular basis to develop suitable GLP-1 receptor antagonist radioligands for in vivo imaging of GLP-1 receptor-expressing tissues in patients.