Somatostatin receptor-targeted radionuclide therapy in patients with gastroenteropancreatic neuroendocrine tumors

Vasoactive intestinal peptide secreting tumour: An overview

Vasoactive intestinal peptide (VIP) secreting tumour (VIPoma) is a rare functional neuroendocrine tumour that typically arises from pancreatic islet cells. These present as sporadic, solitary pancreatic neoplasias with an estimated incidence of one in ten million individuals per year. Only around 5% of VIPomas are associated with multiple endocrine neoplasia type I syndrome. Excessive VIP secretion produces a clinical syndrome characterized by refractory watery diarrhoea, hypokalemia and metabolic acidosis. These coupled with elevated plasma levels of VIP are diagnostic. The majority of VIPomas are malignant and have already metastasized at the time of diagnosis (60%). Metastases occur most frequently in the liver, or regional lymph nodes, lungs, kidneys and bones. Some reports of skin metastases have been documented. Complete surgical resection continues to be the only potentially curative treatment. However, when the neoplasia cannot be excised completely, surgical debulking may provide palliative benefit. Other palliative options have included recently the peptide receptor radionuclide therapy which has shown to be effective and well-tolerated. This article will review all aspects of pancreatic VIPomas highlighting aspects such as clinical presentation, diagnosis and management.

Long-term survival and toxicity in patients with neuroendocrine tumors treated with 177 Lu-octreotate peptide radionuclide therapy

BACKGROUND

Peptide receptor radionuclide therapy (PRRT) has shown favorable results in neuroendocrine tumors (NETs). Long-term safety and efficacy data for ¹⁷⁷ Lu-octreotate PRRT, particularly in combination with chemotherapy, is lacking.

METHODS

The authors conducted a retrospective review of the long-term toxicity and survival outcomes of 104 patients with advanced NETs treated on 4 phase 2 clinical trials with Lutetium-177-octreotate (¹⁷⁷ Lu-octreotate) PRRT, mostly in combination with chemotherapy. Median follow-up was 68 months, which represents the longest follow-up study of ¹⁷⁷ Lu-octreotate PRRT for NETs to date.

RESULTS

Median progression-free survival (PFS) was 37 months, and median overall survival (OS) was 71 months. Five- and 10-year OS were 62% and 29%, and 5- and 10-year PFS were 36% and 21%, respectively, demonstrating ¹⁷⁷ Lu-octreotate can provide durable responses. PRRT was well tolerated with 1.9% of patients developing chronic renal impairment and 1% of patients developing long-term thrombocytopenia. Interestingly, there was a relatively high rate of myelodysplasia (MDS)/leukemia (6.7%), possibly attributable to the longer follow-up (with all except 1 case occurring more than 4 years after PRRT treatment) or to the addition of concurrent chemotherapy.

CONCLUSIONS

Lutetium-177-Octreotate PRRT remains an efficacious and well tolerated treatment in long-term follow-up. For clinicians deciding on the timing of PRRT for individual patients, the 6.7% long-term risk of MDS/leukemia needs to be balanced against the 21% PFS at 10 years.

Aggressive pituitary neuroendocrine tumors: current practices, controversies, and perspectives, on behalf of the EANS skull base section

Aggressive pituitary neuroendocrine tumors (APT) account for 10% of pituitary tumors. Their management is a rapidly evolving field of clinical research and has led pituitary teams to shift toward a neuro-oncological-like approach. The new terminology "Pituitary neuroendocrine tumors" (PitNet) that was recently proposed to replace "pituitary adenomas" reflects this change of paradigm. In this narrative review, we aim to provide a state of the art of actual knowledge, controversies, and recommendations in the management of APT. We propose an overview of current prognostic markers, including the recent five-tiered clinicopathological classification. We further establish and discuss the following recommendations from a neurosurgical perspective: (i) surgery and multi-staged surgeries (without or with parasellar resection in symptomatic patients) should be discussed at each stage of the disease, because it may potentialize adjuvant medical therapies; (ii) temozolomide is effective in most patients, although 30% of patients are non-responders and the optimal timeline to initiate and interrupt this treatment remains questionable; (iii) some patients with selected clinicopathological profiles may benefit from an earlier local radiotherapy and/or chemotherapy; (iv) novel therapies such as VEGF-targeted therapies and anti-CTLA-4/anti-PD1 immunotherapies are promising and should be discussed as 2nd or 3rd line of treatment. Finally, whether neurosurgeons have to operate on "pituitary adenomas" or "PitNets," their role and expertise remain crucial at each stage of the disease, prompting our community to deal with evolving concepts and therapeutic resources.

68Ga-DOTATATE PET/CT Imaging of Refractory Pituitary Macroadenoma Invading the Orbit

ABSTRACT

In addition to gastroenteropancreatic neuroendocrine neoplasms, a wide variety of tumors express somatostatin receptors. Somatostatin receptor imaging, heavily utilized in neuroendocrine oncology, may also have utility in the diagnosis of other neoplasms and raises the possibility of potential therapeutic options. We describe the case of a 60-year-old man who underwent 68Ga-DOTATATE PET/CT, demonstrating an avid invasive pituitary macroadenoma. This mass was persistent and refractory despite traditional treatment options. Because of the avidity, 177Lu-DOTATATE therapy was offered, although not ultimately performed, demonstrating a potential treatment for challenging cases utilizing the principles of theranostics.

Multimodal Non-Surgical Treatments of Aggressive Pituitary Tumors

Up to 35% of aggressive pituitary tumors recur and significantly affect mortality and quality of life. Management can be challenging and often requires multimodal treatment. Current treatment options, including surgery, conventional medical therapies such as dopamine agonists, somatostatin receptor agonists and radiotherapy, often fail to inhibit pituitary tumor growth. Recently, anti-tumor effects of chemotherapeutic drugs such as Temozolomide, Capecitabine, and Everolimus, as well as peptide receptor radionuclide therapy on aggressive pituitary tumors have been increasingly investigated and yield mixed, although sometimes promising, outcomes. The purpose of this review is to provide thorough information on non-surgical medical therapies and their efficacies and used protocols for aggressive pituitary adenomas from pre-clinical level to clinical use.

Accuracy of kidney dosimetry performed using simplified time activity curve modelling methods: a 177Lu-DOTATATE patient study

¹⁷⁷Lu-DOTATATE therapy has been shown to produce encouraging results in treatment of neuroendocrine tumours (NETs). Unfortunately, since dosimetry for radionuclide therapy is considered to be challenging, typically similar amount of radiopharmaceutical is administered to every patient. There is growing evidence that the efficacy of this therapy can be significantly improved by employing personalized protocols, based on the organ-at-risk dosimetry. The aim of this study is to propose a practical and accurate dosimetry protocol based on the simplified acquisition schedules. Data from fifty-three therapy cycles in thirty-nine NET patients were analyzed. Three SPECT/CT scans, acquired at 4 h (D0), 23 h (D1) and 70 h (D3) after injection, were performed. The kidney volume was determined using CT and the activity was determined from quantitative SPECT using an iterative thresholding method. For each dataset, four methods were used to model the time-activity-curves (TAC): M1-two trapezoid segments (0 to D0 and D0 to D1), followed by monoexponential fit to D1  +  D3 data; M2-monoexponential fit to D0  +  D1  +  D3 data; M3 and M4-monoexponential fit to D0  +  D3 and D1  +  D3 data, respectively. Additionally, kidney doses obtained from single time point method using a monoexponential curve with the population mean effective half-life, normalized to activities at D0 or D1 or D3 points, were calculated. The accuracy of simplified dosimetry methods was assessed as the percentage difference relative to doses calculated from M1. The major contribution to the absorbed dose estimate comes from the area under the late time portion of the TAC (D1 to infinity). Therefore, information from the late scan (D3) is crucial for the determination of kidney absorbed doses. Single time point method using monoexponential TAC, with the population mean effective half-life normalized to the late data point (48-72 h for kidneys) produces  <10% deviation in the absorbed dose estimation, thus is recommended for clinical use.

The Role of Adding Somatostatin Analogues to Peptide Receptor Radionuclide Therapy as a Combination and Maintenance Therapy

Purpose: Although somatostatin analogues (SSA) and peptide receptor radionuclide therapy (PRRT) are validated therapies in patients with advanced gastroenteropancreatic neuroendocrine tumors (GEP-NET), it remains unclear whether SSA combined with PRRT or as maintenance therapy can provide prolonged survival compared with patients treated with PRRT alone. In this retrospective study, we aimed to investigate whether there is a survival benefit to adding SSA to PRRT as a combination therapy and/or maintenance therapy.Patients and Methods: The investigation included 168 patients with unresectable GEP-NETs treated at the University Hospital Bonn, Bonn, Germany. The patients were divided into two main groups: PRRT monotherapy (N = 81, group 1) and PRRT plus SSA (N = 87, group 2) as combined therapy with PRRT and/or as maintenance therapy after PRRT.Results: Data for overall survival (OS) were available from 168 patients, of whom 160 had data for progression-free survival (PFS). The median PFS was 27 months in group 1 versus 48 months in group 2 (P = 0.012). The median OS rates were 47 months in group 1 and 91 months in group 2 (P < 0.001). The death-event rates were lower in group 2 (26%) than in group 1 (63%). SSA as a combination therapy with PRRT and/or as a maintenance therapy showed a clinical benefit rate (objective response or stable disease) of 95%, which was significantly higher than group 1 (79%).Conclusions: SSA as a combination therapy and/or maintenance therapy may play a significant role in tumor control in patients with GEP-NET who underwent a PRRT. Clin Cancer Res; 24(19); 4672-9. ©2018 AACR.

Gastro-entero-pancreatic neuroendocrine tumors in multiple endocrine neoplasia type 1: a therapy update

Gastro-entero-pancreatic neuroendocrine tumors (GEP-NETs) are the second most common tumors in multiple endocrine neoplasia type 1 (MEN1), mainly occurring in pancreatic islets and duodenum, usually as multiple tumors. They can manifest as both nonfunctioning and functioning tumors. Currently, surgical removal of GEP-NETs in MEN1 represents the gold standard curative approach. Conventional medical therapies for sporadic GEP-NETs showed to be effective also in a percentage of MEN1 patients. Innovative medical therapies, that have demonstrated to be effective on sporadic GEP-NETs, still need to be evaluated on MEN1 patients in prospective clinical trials and long-term follow-up. This review resumes current knowledge of MEN1 GEP-NETs, discussing surgical and medical approaches, genetic and molecular bases of tumorigenesis, and presenting novel possible drug therapies.

Large-Cell Neuroendocrine Carcinoma of the Esophagus: A Case from Saudi Arabia

Neuroendocrine carcinomas of the esophagus are very rare, and the majority are high grade (poorly differentiated). They occur most frequently in males in their sixth and seventh decades of life. There have been no concrete data published on clinical features or on prognosis. We report a case of large-cell neuroendocrine carcinoma of the esophagus in a 66-year-old Saudi female with progressive dysphagia and weight loss. Upper endoscopy revealed an esophageal ulcerated mass.

Pancreatic Neuroendocrine Tumors: an Update

Pancreatic neuroendocrine tumors (pNETs) are rare and comprise only 1-2 % of all pancreatic neoplastic disease. Although the majority of these tumors are sporadic (90 %), pNETs can arise in the setting of several different hereditary genetic syndromes, most commonly multiple endocrine neoplasia type 1 (MEN1). The presentation of pNETs varies widely, with over 60 % having malignant distant disease at the time of initial diagnosis involving the liver or other distant sites. Functioning pNETs represent approximately 10 % of all pNETs, secrete a variety of peptide hormones, and are responsible for several clinical syndromes caused by profound hormonal derangement. Surgery remains the cornerstone of therapy and the only curative approach. It should be pursued for localized disease and for metastatic lesions amenable to resection. Multimodality therapies, including liver-directed therapies and medical therapy, are gaining increasing favor in the treatment of advanced pNETs. Their utility is multifold and spans from ameliorating symptoms of hormonal excess (functional pNETs) to controlling the local and systemic disease burden (non-functional pNETs). The recent introduction of target molecular therapy has promising results especially for the treatment of progressive well-differentiated G1/G2 tumor. In this review, we summarize the current knowledge and give an update on recent advancements made in the therapeutic strategies for pNETs.

Pretherapeutic estimation of kidney function in patients treated with peptide receptor radionuclide therapy: can renal scintigraphy be safely omitted?

OBJECTIVE

A pretherapeutic assessment of kidney function before peptide receptor radionuclide therapy (PRRT) is considered essential because of the potential renal toxicity associated with PRRT. The aim of this study was to investigate the diagnostic performance of laboratory testing and Tc-mercaptoacetyltriglycine (MAG3) renal scintigraphy with a focus on patients treated with PRRT.

MATERIALS AND METHODS

From January to December 2013 the kidney function of 152 patients was assessed using laboratory tests [creatinine, blood urea nitrogen (BUN), and glomerular filtration rate (GFR)] and Tc-MAG3 clearance. In 27 patients, kidney function was assessed before PRRT. Results of blood tests and Tc-MAG3 renal scintigraphy, considered the reference standard, were compared in the entire patient cohort (n=152) and in both subgroups (PRRT and non-PRRT) using Student's t-test. The cutoff values for the laboratory tests for the prediction of abnormal Tc-MAG3 clearance were determined by means of receiver operating characteristic analysis. In a further mathematical approach using discriminant analysis, a formula was derived for the prediction of kidney function that included all of the serum parameters.

RESULTS

In the PRRT subgroup, laboratory test-derived kidney function correlated significantly with Tc-MAG3 clearance (creatinine: r=-0.429, P=0.037; BUN: r=-0.45, P=0.027; GFR: r=0.44, P=0.022). The correlation was confirmed in the non-PRRT subgroup. The receiver operating characteristic analysis for prediction of abnormal Tc-MAG3 clearance resulted in area under the curves of 0.779 for creatinine alone (sensitivity 74.3%, specificity 71.1%; cutoff ≥0.995 mg/dl) and for the combination of creatinine, BUN, and GFR (sensitivity was 74.3% and specificity was 69.3%).

CONCLUSION

Laboratory tests of kidney function correlate significantly with Tc-MAG3 clearance. Because of the moderate accuracy for laboratory tests, Tc-MAG3 clearance is recommended as a standard test to assess kidney function before PRRT.

Peptide receptor radionuclide therapy in a patient with disabling non-functioning pituitary adenoma

Non-functioning pituitary adenoma (NFPA) with higher proliferation index (WHO II) are often a therapeutical challenge. Low somatostatin receptor expression in these tumors usually prevents a treatment with somatostatin analogs. In 1996, a 55-year-old patient was referred due to right-sided headache. A pituitary macroadenoma with infiltration into the right cavernous sinus was diagnosed. There was no visual field deficit and the clinical and biochemical work up was consistent with a NFPA. The patient underwent transsphenoidal surgery. Residual adenoma remained in the right cavernous sinus. Histologically, a null-cell adenoma with a high proliferation index was documented (MIB-1: 11.6%, WHO II). Somatostatin receptor autoradiography was performed in the surgical specimen showing a homogenous expression of sst2 receptors. Radiosurgery was completed with stable disease for 8 years. In 2004, the patient was diagnosed with an incomplete palsy of the right oculomotorius nerve and a significant increase in the volume of the adenoma in the right cavernous sinus. After a positive Octreoscan(®) the patient consented to an experimental therapy approach using Lutetium DOTATOC (3 × 200 mCi). The palsy of the oculomotorius nerve improved and remained stable until today (March 2013), the follow-up MRI scans demonstrated stable disease. This is the first case of a patient with a NFPA (WHO II) in whom PRRT successfully improved the local complications of the tumor for more than 8 years after ineffective surgery and gamma knife therapy. The determination of sst2 in vitro using autoradiography and in vivo by Octreoscan was instrumental to administer this therapy in a challenging situation.

Peptide receptor radionuclide therapy with 177Lu-DOTATATE for patients with somatostatin receptor-expressing neuroendocrine tumors: the first US phase 2 experience

OBJECTIVE

Peptide receptor radionuclide therapy with radiolabeled somatostatin analogs is a novel method of treatment in patients with metastatic neuroendocrine tumors (NETs). For the first time in the United States, we present preliminary results of the treatment with Lutetium (177)(Lu) DOTATATE in patients with progressive NETs.

METHODS

Thirty-seven patients with grade 1 and grade 2 disseminated and progressive gastroenteropancreatic NET were enrolled in a nonrandomized, phase 2 clinical trial. Repeated cycles of 200 mCi (7.4 GBq; ±10%) were administered up to the cumulative dose of 800 mCi (29.6 GBq; ±10%).

RESULTS

Among 32 evaluable patients, partial response and minimal response to treatment were seen in 28% and 3%, respectively, and stable disease was seen in 41% of patients. A total of 28% had progressive disease. A response to treatment was significantly associated with lower burden of disease in the liver. No significant acute or delayed hematologic or kidney toxicity was observed. An impressive improvement of performance status and quality of life were seen after Lu-DOTATATE therapy.

CONCLUSIONS

Treatment with multiple cycles of (177)Lu-DOTATATE peptide receptor radionuclide therapy is well tolerated. This treatment results in control of the disease in most patients, whereas systemic toxicities are limited and reversible. Quality of life is also improved.

Nonfunctional pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors are a group of rare, heterogeneous neoplasms that have been increasing in incidence the past few decades largely because of the diagnosis of pancreatic incidentalomas on cross-sectional imaging. Although these tumors are classically associated with clinical syndromes that result from excess secretion of particular hormones, most pancreatic neuroendocrine tumors are nonfunctional tumors presenting with symptoms secondary to mass effect, metastatic disease, or as incidental findings. This article reviews the diagnostic algorithm, surgical management, and available systemic therapies for nonfunctional pancreatic neuroendocrine tumors.

Olfactory receptor 51E1 as a novel target for diagnosis in somatostatin receptor-negative lung carcinoids

Somatostatin receptors (SSTRs) may be used in lung carcinoids (LCs) for diagnosis and therapy, although additional targets are clearly warranted. This study aimed to investigate whether olfactory receptor 51E1 (OR51E1) may be a potential target for LCs. OR51E1 coding sequence was analyzed in LC cell lines, NCI-H727 and NCI-H720. OR51E1 transcript expression was investigated in LC cell lines and frozen specimens by quantitative real-time PCR. OR51E1, SSTR2, SSTR3, and SSTR5 expression was evaluated by immunohistochemistry on paraffin-embedded sections of 73 typical carcinoids (TCs), 14 atypical carcinoids (ACs), and 11 regional/distant metastases and compared with OctreoScan data. Immunohistochemistry results were rendered semiquantitatively on a scale from 0 to 3, taking into account the cellular compartmentalization (membrane vs cytoplasm) and the percentage of tumor cells (<50 vs >50%). Our results showed that WT OR51E1 transcript was expressed in both LC cell lines. OR51E1 mRNA was expressed in 9 out of 12 TCs and 7 out of 9 ACs (P=NS). Immunohistochemically, OR51E1, SSTR2, SSTR3, and SSTR5 were detected in 85, 71, 25, and 39% of TCs and in 86, 79, 43, and 36% of ACs respectively. OR51E1 immunohistochemical scores were higher or equal than those of SSTRs' in 79% of TCs and 86% of ACs. Furthermore, in the LC cases where all SSTR subtypes were lacking, membrane OR51E1 expression was detected in 10 out of 17 TCs and 1 out of 2 ACs. Moreover, higher OR51E1 immunohistochemical scores were detected in 5 out of 6 OctreoScan-negative LC lesions. Therefore, the high expression of OR51E1 in LCs makes it a potential novel diagnostic target in SSTR-negative tumors.

Accurate assessment of long-term nephrotoxicity after peptide receptor radionuclide therapy with (177)Lu-octreotate

PURPOSE

Renal radiation during peptide receptor radionuclide therapy (PRRT) may result in glomerular damage, a potential reduction of glomerular filtration rate (GFR) and ultimately lead to renal failure. While reported PRRT nephrotoxicity is limited to data derived from serum creatinine-allowing only approximate estimates of GFR-the aim of this study is to accurately determine PRRT-induced long-term changes of renal function and associated risk factors according to state-of-the-art GFR measurement.

METHODS

Nephrotoxicity was analysed using (99m)Tc-diethylenetriaminepentaacetic acid (DTPA) clearance data of 74 consecutive patients with gastroenteropancreatic neuroendocrine tumours (GEP NET) undergoing PRRT with (177)Lu-octreotate. The mean follow-up period was 21 months (range 12-50) with a median of five GFR measurements per patient. The change of GFR was analysed by linear curve fit. Potential risk factors including diabetes mellitus, arterial hypertension, previous chemotherapy, renal impairment at baseline and cumulative administered activity were analysed regarding potential impact on renal function loss. In addition, Common Terminology Criteria for Adverse Events (CTCAE) v3.0 were used to compare nephrotoxicity determined by (99m)Tc-DTPA clearance versus serum creatinine.

RESULTS

The alteration in GFR differed widely among the patients (mean -2.1 ± 13.1 ml/min/m(2) per year, relative yearly reduction -1.8 ± 18.9%). Fifteen patients (21%) experienced a mild (2-10 ml/min/m(2) per year) and 16 patients (22%) a significant (>10 ml/min/m(2) per year) decline of GFR following PRRT. However, 11 patients (15%) showed an increase of >10 ml/min/m(2) per year. Relevant nephrotoxicity according to CTCAE (grade ≥3) was observed in one patient (1.3%) with arterial hypertension and history of chemotherapy. Nephrotoxicity according to serum creatinine was discordant to that defined by GFR in 15% of the assessments and led to underestimation in 12% of patients. None of the investigated factors including cumulative administered activity contributed to the decline of renal function.

CONCLUSION

Serious nephrotoxicity after PRRT with (177)Lu-octreotate is rare (1.3%). However, slight renal impairment (GFR loss >2 ml/min/m(2) per year) can frequently (43%) be detected by (99m)Tc-DTPA clearance assessments. Cumulative administered activity of (177)Lu-octreotate is not a major determinant of renal impairment in our study.

Systemic therapy for advanced pancreatic neuroendocrine tumors

Neuroendocrine tumors (NETs) occur throughout the body, and share similar histologic characteristics. However, it has become increasingly evident that pancreatic NETs tend to respond differently to therapeutic agents than do other NET subtypes. In most cases, systemic therapy has been more effective in NETs of pancreatic origin than in NETs arising from other locations. Traditional systemic treatment options for pancreatic NETs include somatostatin analogs or cytotoxic chemotherapy. Recently, the biologically targeted agents everolimus and sunitinib were approved for use in patients with metastatic disease. Novel agents, as well as novel drug combinations, are currently under investigation.

Management of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors account for 1% to 2% of pancreatic neoplasms and may occur sporadically or as part of a hereditary syndrome. Patients may present with symptoms related to hormone secretion by functional tumors or to locally advanced or metastatic nonfunctional tumors. Asymptomatic pancreatic neuroendocrine tumors are increasingly detected incidentally during abdominal imaging performed for other reasons. The management of localized pancreatic neuroendocrine tumors is surgical resection. Hepatic metastases are common and their management involves a variety of liver-directed therapies, which should be tailored according to extent of disease, symptoms, presence of extrahepatic metastases, and patient performance status.

Clinical presentation, recurrence, and survival in patients with neuroendocrine tumors: results from a prospective institutional database

The rarity of neuroendocrine tumors (NET) has contributed to a paucity of large epidemiologic studies of patients with this condition. We characterized presenting symptoms and clinical outcomes in a prospective database of over 900 patients with NET. We used data from patient questionnaires and the medical record to characterize presenting symptoms, disease-free survival (DFS), and overall survival (OS). The majority of patients in this database had gastroenteropancreatic NET. The median duration of patient-reported symptoms before diagnosis was 3.4 months; 19.5% reported durations from 1 to 5 years, 2.5% from 5 to 10 years, and 2% >10 years. The median DFS among patients with resected small bowel NET or pancreatic NET (panNET) was 5.8 and 4.1 years respectively. After correcting for left truncation bias, the median OS was 7.9 years for advanced small bowel NET and 3.9 years for advanced panNET. Chromogranin A (CGA) above twice the upper limit of normal was associated with shorter survival times (hazard ratios 2.8 (1.9, 4.0) P<0.001) in patients with metastatic disease, regardless of tumor subtype. Our data suggest that while most NET patients are diagnosed soon after symptom onset, prolonged symptom duration before diagnosis is a prominent feature of this disease. Though limited to observations from a large referral center, our observations confirm the prognostic value of CGA and suggest that median survival durations may be shorter than that reported in other institutional databases.

Bombesin analogue-mediated delivery preferentially enhances the cytotoxicity of a mitochondria-disrupting peptide in tumor cells

Tumor-homing peptides that recognize specific markers on tumor cells have shown potential as drug carriers for targeted cancer therapy. Bombesin receptors are frequently overexpressed or ectopically expressed in a wide range of human tumors. Bombesin and its analogues have been widely used as drug carriers for tumor imaging and tumor therapy. However, the cargos used in previous studies, including radioactive and chemotherapeutic agents, are usually small molecules. Mitochondrial-disrupting peptides depolarize the mitochondria and trigger apoptosis after entering tumor cells. We are interested in whether the bombesin analogue, Bn(6–14), which contains a bombesin receptor-binding motif, can specifically deliver the mitochondria-disrupting peptide, B28, to tumor cells. To this end, we created a chimeric peptide, B28Bn(6–14), by conjugating B28 to Bn(6–14) at its N-terminus. The cytotoxicity of B28Bn(6–14) in tumor cells was much stronger than unconjugated B28. The IC₅₀ values of B28Bn(6–14) in tumor cells (1.7–3.5 µM) were approximately 10 times lower than B28. However, conjugation of B28 to Bn(2–7), which lacks the bombesin receptor-binding motif, did not increase its cytotoxicity. In addition, the IC₅₀ values of B28Bn(6–14) in tumor cells (1.7–3.5 µM) was 3–10 times lower than in normal cells (10.8–16.8 µM). We found that selective binding of B28Bn(6–14) to tumor cells is Bn(6–14)-dependent. Upon entering the tumor cell, B28Bn(6–14) accumulated in the mitochondria and triggered caspase-dependent apoptosis. Intratumoral and intraperitoneal administration of B28Bn(6–14) substantially suppressed the growth of DU145 tumor xenografts in mice. These results demonstrate that Bn(6–14) is able to deliver the mitochondria-disrupting peptide to tumor cells, and B28Bn(6–14) should be further developed as novel anti-cancer agent.

Olfactory receptor 51E1 protein as a potential novel tissue biomarker for small intestine neuroendocrine carcinomas

OBJECTIVE

Late diagnosis hinders proper management of small intestine neuroendocrine carcinoma (SI-NEC) patients. The olfactory receptor, family 51, subfamily E, member 1 (OR51E1) has been reported as a potential novel SI-NEC marker, without protein expression recognition. Thus, we further studied whether the encoded protein may be a novel SI-NEC clinical biomarker.

DESIGN

OR51E1 coding sequence was cloned using total RNA from SI-NEC patient specimens. Quantitative real-time PCR analysis explored OR51E1 expression in laser capture microdissected SI-NEC cells and adjacent microenvironment cells. Moreover, immunohistochemistry investigated OR51E1 protein expression on operation and biopsy material from primary SI-NECs, mesentery, and liver metastases from 70 patients. Furthermore, double immunofluorescence studies explored the potential co-localization of the vesicular monoamine transporter 1 (SLC18A1, generally referred to as VMAT1) and OR51E1 in the neoplastic cells and in the intestinal mucosa adjacent to the tumor.

RESULTS

OR51E1 coding sequence analysis showed absence of mutation in SI-NEC patients at different stages of disease. OR51E1 expression was higher in microdissected SI-NEC cells than in the adjacent microenvironment cells. Furthermore, both membranous and cytoplasmic OR51E1 immunostaining patterns were detected in both primary SI-NECs and metastases. Briefly, 18/43 primary tumors, 7/28 mesentery metastases, and 6/18 liver metastases were 'positive' for OR51E1 in more than 50% of the tumor cells. In addition, co-localization studies showed that OR51E1 was expressed in >50% of the VMAT1 immunoreactive tumor cells and of the enterochromaffin cells in the intestinal mucosa adjacent to the tumor.

CONCLUSION

OR51E1 protein is a potential novel clinical tissue biomarker for SI-NECs. Moreover, we suggest its potential therapeutic molecular target development using solid tumor radioimmunotherapy.

Radiological and nuclear medicine imaging of gastroenteropancreatic neuroendocrine tumours

Neuroendocrine tumours (NETs) comprise a heterogeneous group of neoplasms with very varying clinical expression. A functioning NET, for instance in the pancreas, may be very small and yet give rise to severe endocrine symptoms whereas a patient with a small bowel tumour may present with diffuse symptoms and disseminated disease with a palpable bulky liver. Imaging of NETs is therefore challenging and the imaging needs in the various patients are diverse. The basic modalities for NET imaging are computed tomography (CT) or magnetic resonance imaging (MRI) in combination with somatostatin receptor imaging (SMI) by scintigraphy with 111In-labelled octreotide (OctreoScan) or more recently by positron emission tomography (PET) with 68Ga-labelled somatostatin analogues. In this review these various morphological and functional imaging modalities and important methodological aspects are described. Imaging requirements for the various types of NETs are discussed and typical image findings are illustrated.

Radiological safety concerns for the accelerator production of diagnostic and therapeutic radionuclides in a university setting

Accelerator production of radionuclides for diagnostic and therapeutic research at a university has many advantages. Radionuclides not commonly available through commercial suppliers may be readily produced for innovative research applications. Loss of material due to decay in transit is minimized, and product lead times may be significantly reduced. Furthermore, graduate students and research assistants have the opportunity to gain considerable hands-on experience during the production, extraction, and processing operations. However, the benefits of implementing accelerator production into an existing radiological protection program must be balanced against increased safety procedures and maintenance of as-low-as-reasonably-achievable work practices. This article outlines the basics for radioactive material production and corresponding issues in radiological protection associated with the production, use, and disposal on a college campus.

Therapy of metastatic pancreatic neuroendocrine tumors (pNETs): recent insights and advances

Neuroendocrine tumors (NETs) [carcinoids, pancreatic neuroendocrine tumors (pNETs)] are becoming an increasing clinical problem because not only are they increasing in frequency, but they can frequently present with advanced disease that requires diagnostic and treatment approaches different from those used in the neoplasms that most physicians are used to seeing and treating. In the past few years there have been numerous advances in all aspects of NETs including: an understanding of their unique pathogenesis; specific classification systems developed which have prognostic value; novel methods of tumor localization developed; and novel treatment approaches described. In patients with advanced metastatic disease these include the use of newer chemotherapeutic approaches, an increased understanding of the role of surgery and cytoreductive methods, the development of methods for targeted delivery of cytotoxic agents, and the development of targeted medical therapies (everolimus, sunitinib) based on an increased understanding of the disease biology. Although pNETs and gastrointestinal NETs share many features, recent studies show they differ in pathogenesis and in many aspects of diagnosis and treatment, including their responsiveness to different therapies. Because of limited space, this review will be limited to the advances made in the management and treatment of patients with advanced metastatic pNETs over the past 5 years.

Current status and perspectives of targeted therapy in well-differentiated neuroendocrine tumors

Although neuroendocrine tumors (NET) are a relatively rare malignancy, the reported incidence is increasing, and some of the current treatment options are limited in their efficacy. Standard first-line therapy for metastatic small bowel NET includes somatostatin analogs. Although these agents can provide symptom relief and can delay disease progression in many patients, ultimately, new treatments are required for patients with progressive disease. In recent years, there has been considerable interest in developing agents specifically targeted against some of the pathways known to be involved in cancer cell growth, survival and invasion. In 2011, the mammalian target of rapamycin (mTOR) inhibitor everolimus and the tyrosine kinase inhibitor sunitinib were approved for the treatment of pancreatic NET. Clinical trials evaluating novel targeted agents are ongoing, both as single agents and in combination regimens. We review the current clinical status of these potential new treatments and highlight those with particular promise for the management of well-differentiated NET.

Targeting aurora kinases with danusertib (PHA-739358) inhibits growth of liver metastases from gastroenteropancreatic neuroendocrine tumors in an orthotopic xenograft model

PURPOSE

Aurora kinases play a crucial role in cell-cycle control. Uncontrolled expression of aurora kinases causes aneuploidy and tumor growth. As conservative treatment options for advanced gastroenteropancreatic neuroendocrine tumors (GEP-NET) are disappointing, aurora kinases may be an interesting target for novel therapeutic strategies.

EXPERIMENTAL DESIGN

Human GEP-NETs were tested for aurora kinase expression. The efficacy of the new aurora kinase inhibitor danusertib was evaluated in two human GEP-NET cell lines (BON1 and QGP) in vitro and in vivo.

RESULTS

The majority of ten insulinomas and all 33 nonfunctional pancreatic or midgut GEP-NETs expressed aurora A despite a mostly high degree of cell differentiation. Both human GEP-NET cell lines expressed aurora kinase A and B, and high Ser10 phosphorylation of histone H3 revealed increased aurora B activity. Remarkably, danusertib led to cell-cycle arrest and completely inhibited cell proliferation of the GEP-NET cells in vitro. Decreased phosphorylation of histone H3 indicated effective aurora B inhibition. In a subcutaneous murine xenograft model, danusertib significantly reduced tumor growth in vivo compared with controls or mice treated with streptozotocine/5-fluorouracil. As a consequence, decreased levels of tumor marker chromogranin A were found in mouse serum samples. In a newly developed orthotopic model for GEP-NET liver metastases by intrasplenic tumor cell transplantation, dynamic MRI proved significant growth inhibition of BON1- and QGP-derived liver metastases.

CONCLUSIONS

These results show that danusertib may impose a new therapeutic strategy for aurora kinase expressing metastasized GEP-NETs.

New treatment strategies in advanced neuroendocrine tumours

Malignant well-differentiated neuroendocrine tumours of the pancreas and the gastrointestinal tract are rare and clinically challenging heterogeneous neoplasms. This review focuses on neuroendocrine tumours grade 1 and grade 2 (new WHO classification 2010), in comparison to the neuroendocrine tumours grade 3 group, corresponding to poorly differentiated neuroendocrine carcinomas. Surgical resection of the primary and metastases remains the only curative treatment, however many patients with neuroendocrine tumours are diagnosed once unresectable metastases have occurred; management of functioning syndromes with somatostatin analogues remains the priority. Pasireotide, a new somatostatin analogue, is currently undergoing evaluation for carcinoid syndrome. Treatment options for advanced neuroendocrine tumours differ from pancreatic gastrointestinal tract neuroendocrine tumours: (a) in pancreatic neuroendocrine tumours, streptozotocin-based chemotherapies are challenged by other cytotoxic agents (dacarbazine, temozolomide and oxaliplatin); two randomized, placebo-controlled phase III studies have demonstrated that everolimus and sunitinib significantly improved progression-free-survival; (b) in midgut neuroendocrine tumours, octreotide improved time-to-progression in patients with a low proliferation index and low liver burden; preliminary data suggesting efficacy of bevacizumab are still to be confirmed; the effect of everolimus associated with octreotide was almost significant on progression-free-survival in a phase III trial. Liver-directed therapies are effective in both tumour types. New techniques of embolization need further evaluation and must be formally compared to other therapies. Finally, peptide receptor radionuclide therapy has shown promising activity in non-comparative studies in advanced neuroendocrine tumours.

Neuroendocrine tumors of the pancreas

PURPOSE OF REVIEW

Pancreatic neuroendocrine tumors (PNETs) are rare tumors, with an incidence of one per 100, 000 individuals per year, and they account for 1-2% of all pancreatic neoplasms. PNETs are a heterogeneous group with varying clinical presentation, tumor biology and prognosis. This article reviews the current diagnostic strategy and treatment armamentarium for PNETs. Special attention is paid to recent and ongoing developments in treatment, particularly with regards to multimodality treatment and newer systemic therapies for unresectable disease.

RECENT FINDINGS

There has been significant progress in the genetic understanding of hereditary syndromes in regards to PNETs, as well as in the diagnosis and treatment of resectable and nonresectable PNETs. Whereas surgical therapy remains the most advisable therapy for resectable neuroendocrine tumors of the pancreas, there have been significant recent advances in systemic therapy for those with unresectable disease. Results from recent clinical trials examining mammalian target of rapamycin inhibitors and tyrosine kinase inhibitors for unresectable disease are promising in expanding treatment options for metastatic PNETs.

SUMMARY

Neuroendocrine tumors of the pancreas are a heterogeneous group of tumors with varying clinical presentation, tumor biology and prognosis. Clinicians must be aware of the variety of manifestations of this disease, as well as the role of systemic chemotherapy in treatment of unresectable disease.

Pregnant with metastatic neuroendocrine tumour of the ovary: what now?

Neuroendocrine tumours (NET) are a heterogeneous group of neoplasms commonly occurring in the gastrointestinal tract or lungs but can occur in other regions. Primary ovarian NET account for 5% of all NET and 0.1% of all ovarian malignancies. In metastatic disease, the therapeutic goal is to extend survival and to improve quality of life. As these tumours express somatostatin receptors, somatostatin analogues are frequently used to control symptoms. Here we present a case of a pregnant woman with an ovarian NET with liver metastases and carcinoid syndrome who was treated with the somatostatin analogue, Octreotide LAR. We also summarize reported data of the use of somatostatin analogues during pregnancy.

Therapeutic monitoring of gastroenteropancreatic neuroendocrine tumors: the challenges ahead

BACKGROUND

Gastroenteropancreatic neuroendocrine tumors (NETs), a heterogeneous family of tumors arising in a variety of anatomic sites, are generally well differentiated and often metastatic at diagnosis. Morphologic and functional imaging modalities have vastly improved the understanding and diagnosis of NETs. However, use of conventional imaging techniques and response criteria to assess treatment response is often complicated by the clinical course and cytostatic nature of oncologic treatments for NETs.

MATERIALS AND METHODS

The means of therapeutic monitoring discussed in this review were based on a PubMed search of the medical literature and on the clinical expertise of the authors.

RESULTS

Morphology-based criteria for assessing tumor response in general oncology are presented, along with their limitations for assessing response in gastrointestinal and pancreatic NETs. Functional imaging and preliminary response criteria incorporating functional imaging are presented as possible solutions to monitoring treatment response in NETs.

CONCLUSIONS

Morphology-based criteria to assess tumor response have limitations for NETs, which are often slow growing and frequently demonstrate low response rates when based on conventional radiological criteria. Furthermore, many NET treatments do not induce cytotoxic effects despite demonstrated clinical benefit. Novel imaging techniques are available which have the potential to measure changes in tumor physiology and metabolism. These include (68)Ga-labelled somatostatin analogs for PET/CT-based monitoring of NET, molecular imaging with PET tracers that are not based on somatostatin receptor targeting, and functional MRI. These techniques should be explored as options for monitoring treatment in patients with NET.

Clinical review: Pituitary carcinoma: difficult diagnosis and treatment

CONTEXT

Although pituitary tumors are common, pituitary carcinoma is very rare and is only diagnosed when pituitary tumor noncontiguous with the sellar region is demonstrated. Diagnosis is difficult, resulting in delays that may adversely effect outcome that is traditionally poor. Barriers to earlier diagnosis and management strategies for pituitary carcinoma are discussed.

EVIDENCE ACQUISITION

PubMed was employed to identify relevant studies, a review of the literature was conducted, and data were summarized and integrated from the author's perspective.

EVIDENCE SYNTHESIS

The available data highlight the difficulties in diagnosis and management and practical challenges in conducting clinical trials in this rare condition. They suggest that earlier diagnosis with aggressive multimodal therapy may be advantageous in some cases.

CONCLUSIONS

Although pituitary carcinoma remains difficult to diagnose and treat, recent developments have led to improved outcomes in selected cases. With broader use of molecular markers, efforts to modify current histopathological criteria for pituitary carcinoma diagnosis may now be possible. This would assist earlier diagnosis and, in combination with targeted therapies, potentially improve long-term survival.

New therapeutic options for metastatic malignant insulinomas

Insulinomas are the most common, functioning, pancreatic neuroendocrine tumours. The great majority (>90%) of insulinomas are nonmetastatic at presentation and can be surgically cured. The <10% patients with distant (liver-bone) metastases have a median survival of < 2 years. Everolimus and sunitinib have been recently introduced as targeted therapies for metastatic pancreatic neuroendocrine tumours. An additional advantage of everolimus in the treatment of patients with metastatic insulinomas is its capability to increase blood glucose levels. Peptide receptor radiotherapy using radiolabelled somatostatin analogues has also been shown to be successful in controlling tumour growth of metastatic pancreatic neuroendocrine tumours. In patients with metastatic insulinomas, this therapeutic modality was also effective in controlling hypoglycaemia, even in the presence of tumour regrowth. With the introduction of these new therapeutic modalities, the therapeutic arsenal for the 'tailor-made' approach of patients with metastatic insulinomas is further expanded.