High Expression Of Somatostatin Receptors Research Articles

Efficacy and Safety of 225 Ac-DOTATATE in the Treatment of Neuroendocrine Neoplasms With High SSTR Expression.

We aimed to evaluate the efficacy and safety of 225 Ac-DOTATATE targeted α therapy (TAT) in various neuroendocrine neoplasms (NENs) with high somatostatin receptor (SSTR) expression. This single-center prospective study included 10 patients with histologically diagnosed NENs that exhibited increased SSTR expression on 68 Ga-DOTATATE PET/CT imaging. All patients received 225 Ac-DOTATATE TAT. The primary end points were molecular imaging-based response and disease control rate (DCR), measured using the slightly modified Positron Emission Tomography Response Criteria in Solid Tumors 1.0. The secondary end points were adverse event profiles and clinical responses. The adverse event profile was determined according to the Common Terminology Criteria for Adverse Events version 5.0. Clinical response was assessed using the EORTC QLQ-C30 v3.0 (European Organization for Research and Treatment of Cancer Core Quality of Life questionnaire version 3.0). A molecular imaging-based partial response was observed in 40% of all patients, SD in 40%, PD in 20%, and DCR in 80%. The DCR was 83.3% (5/6) in patients who were previously treated with 177 Lu-DOTATATE. According to the EORTC QLQ-C30 v3.0 score, most symptoms improved after 225 Ac-DOTATATE treatment, with only diarrhea showing no improvement. Grade III/IV hematological, kidney, and liver toxicities were not observed. The median follow-up time was 14 months (7-22 months), and no deaths were reported. This initial study suggests that 225 Ac-DOTATATE is a potentially promising option for treating NENs with elevated SSTR expression, with an acceptable toxicity profile and well-tolerated adverse effects.

177Lu-DOTATATE (Lutathera) Therapy in 68Ga-DOTATATE PET/CT-Negative Liver Metastases of a Neuroendocrine Tumor.

A 73-year-old man with metastatic pancreatic neuroendocrine tumor was evaluated with 68Ga-DOTATATE PET/CT for peptide receptor radionuclide therapy. Both PET-positive and negative lesions were seen in the liver, along with extrahepatic metastases. Histopathology was obtained from one of the PET-negative liver lesions to exclude secondary malignancy. Histology confirmed a well-differentiated (G2) metastasis of pNET with high somatostatin receptor expression. We initiated peptide receptor radionuclide therapy with close monitoring of the PET-negative liver metastases. We present a rare case, where posttherapeutic scintigraphy revealed vigorous uptake of 177Lu-DOTATATE even in the 68Ga-DOTATATE PET-negative liver metastases. Follow-up PET/CT showed a partial response to therapy.

SAT610 Multiple Endocrine Neoplasia Type 1 - The First Reported Case In An Indigenous Australian

Abstract Disclosure: E. Mignone: None. K. Neal: None. Background: Multiple Endocrine Neoplasia type 1 (MEN1) is a rare and under recognised syndrome. It has not been previously reported in Indigenous Australians for this reason. Clinical Case: A 48-year-old Indigenous Australian female was consulted on by an inpatient endocrine team in March 2020 for persistent hypercalcaemia on a background of a parathyroidectomy in 2011 for primary hyperparathyroidism (PHPTH). She was admitted to a remote Australian hospital for investigation and management of acute on chronic abdominal pain. Relevant medical history included a parathyroidectomy at age 40, multiple PE/DVT, MI, AF, CTEPH, right heart failure, HTLV-1 and recurrent abdominal pain presumed secondary to GORD. Gastroscopy from 2013 revealed chronic gastritis with hundreds of gastric polyps discovered on subsequent gastroscopy in 2015. The young age of PHPTH combined with her chronic gastritis and polyps prompted neuroendocrine tumour (NET) screening, including MEN1. At time of consult in 2020, laboratory studies were consistent with recurrence of PHPTH with a corrected calcium of 2.9 mmol/L (2.15-2.57mmol/L), serum PTH level 31.5 pmol/L (1-7pmol/L), vitamin D level 30 nmol/L, 24-hour urinary calcium variable between low and high. NET markers were markedly elevated with a gastrin level of 14042 ng/L (<100 ng/L), pancreatic polypeptide 2905 pmol/L (<55 pmol/L), urine 5HIAA ratio 8 mmol/L (<4 mmol/L), vasoactive intestinal peptide and glucagon levels normal. Pituitary studies, serum calcitonin, plasma metanephrines and PTH related protein levels were within normal limits. A CT of the abdomen showed thickened gastric folds, and persistent liver and IVC lesions from 2018. A diagnosis of Zollinger Ellison Syndrome (ZES) was made. Eventually, genetic testing was positive for a rare heterozygous variant of c.207dupC in exon 2 of MEN1 gene. A 68-gallium-DOTATATE PET/CT showed multiple avid pancreatic, gastric, nodal and liver lesions with high somatostatin receptor expression, suggestive of a neuroendocrine malignancy. Treatment was based largely on symptom control due to poor overall prognosis from underlying cardiorespiratory comorbidities. Abdominal pain from ZES was managed with a high dose PPI, H2 receptor antagonist and subcutaneous somatostatin analogue were trialled. Hypercalcaemia was treated with IV bisphosphonate therapy. Calcimimetic analogues were considered however patient declined. Genetic counselling was attempted however many cultural and logistical barriers were identified and family declined further testing. Unfortunately, our patient died in 2021 from presumed multifactorial respiratory failure. Conclusion: High index of suspicion is required to diagnose MEN1. This is particularly true within the Indigenous Australian population, with no prior documented cases reported. Presentation: Saturday, June 17, 2023

Predictors of long-term remission in acromegaly – an updated review

Abstract Acromegaly is a rare chronic disorder due to growth hormone (GH) - secreting pituitary tumor. The first-line treatment of acromegaly is a transsphenoidal adenomectomy. Surgical remission rates range from 30-50% for macroadenomas to 70-90% for microadenomas. Thus in patients with active acromegaly after surgery, medical treatment is recommended. Treatment outcome on medical therapy differs a lot depending on medications. The aim of this paper is to summerize the current knowledge of factors predicting acromegaly remission after surgery and biochemical control on medical treatment. Factors affecting treatment outcome, not related to the patient and the tumor, are neurosurgeon’s experience and visualisation tools used during surgery. Younger patients, as well as women tend to achieve acromegaly remission after surgery less often. Patients with lower GH and insulin-like growth factor-1 (IGF-1) concentrations at diagnosis, in oral glucose tolerance test (OGTT) and postoperatively have a greater chance of surgical remission. However, some publications do not confirm that. Patients presenting with larger and more invasive tumors achieve surgical remisson less often. Hypointensive tumors on T2-weighted magnetic resonance imaging (MRI) scans are associated with better response to first-generation somatostatin receptor ligands (SRLs) and to pasireotide. Pathologic factors increasing the chance of acromegaly remission are densely granulated tumors, lower Ki-67 index, high expression of somatostatin receptors (SSTRs) and high expression of E-cadherin. A thorough analysis of the abovementioned factors predicting the treatment outcome in acromegaly may be helpful for selecting the best treatment option for each patient.

Gastrointestinal: Pancreatic NETs with GCGR heterozygous mutation: Mahvash disease.

A 61 year old female was found to have a pancreatic tumor in 2013. Preoperative laboratory tests showed fasting and 2-h postprandial glucagon levels were more than 400 pg/mL (upper limit, 150 pg/mL) with normal gastrin, blood glucose, and insulin. Preoperative contrast-enhanced CT (CECT) showed diffusely enlarged and inhomogeneously enhanced pancreas with a 2-cm high-density tumor in the pancreatic body. The tumor was obviously enhanced (Fig. 1a–c). Octreotide imaging showed high somatostatin receptor expression in the tumor. The patient underwent subtotal distal pancreatectomy and splenectomy. On postoperative pathological examination, two gray and white solid tumors were found, measuring 1.2 and 2 cm, respectively. On histology, diffuse hyperplastic islets, dysplasia, and microadenomas were detected in residual pancreatic tissue and the pancreatic resected stump. The two lesions were immune-positive for Ki-67 (index 1%), chromogranin A, synaptophysin, E-cadherin, glucagon, gastrin, and insulin (partial) (Fig. 2). The patient was treated with octreotide acetate 20 mg per injection after surgery. But postoperative fasting glucagon level was still high, fluctuating from 513.16 to 3197.49 during 7-year follow-up. Meanwhile, postoperative CECT showed enlargement of the residual pancreatic head (Fig. 1d). Whole-genome sequencing of peripheral blood demonstrated heterozygous mutation of c.1345C>T, which lead to premature termination of translation, and c.922C>T, which lead to arginine replaced by tryptophan. The case was finally diagnosed as Mahvash disease. Mahvash disease is a rare autosomal recessive hereditary pancreatic neuroendocrine neoplasms caused by defective glucagon receptor gene (GCGR) in the liver and associated reactive pancreatic α-cell hyperplasia. Although whole-genome sequencing demonstrated two heterozygous mutations of GCGR, the clinical and pathological features highly suggested Mahvash diagnosis. Diffusely enlarged and unevenly enhanced pancreas indicated coexistence of hyperplastic α cell, hyperplastic islets, and microadenomas. Significant hyperglucagonemia without glucagonoma syndrome further strengthen diagnostic confidence. Most Mahvash diseases were homozygous mutation, and heterozygous mutation are extremely rare. However, reports of patients with heterozygous mutation often showed sub-centimeter lesions (5.5 mm reported by Miller et al. and 5 mm reported by Henopp et al.). To our knowledge, this is the first time large lesions (>1 cm) has been reported in patient with heterozygous mutation of GCGR. There is possibility that heterozygous mutation of GCGR can also be Mahvash disease.

Detection of "Incidentalomas" on Brain and Body 68Ga-DOTATOC-PET Scans: A Retrospective Study and Case Illustration.

One of the main limitations of standard imaging modalities is microscopic tumor extension, which is often difficult to detect on magnetic resonance imaging (MRI) and computer tomography (CT) in the early stages of the tumor. (68)Ga-DOTA(0)-Phe(1)-Tyr(3)-octreotide positron-emission tomography/computed tomography (68Ga-DOTATOC PET/CT) has shown efficacy in detecting lesions previously undiagnosed by neuroimaging modalities, such as MRI or CT, and has enabled the detection of multiple benign tumors (like multiple meningiomas in a patient presenting with a single lesion on MRI) or additional secondary metastatic locations. We retrospectively reviewed data from the Cannizzaro Hospital on brain and body 68Ga-DOTATOC PET/CT "incidentalomas", defined as tumors missed on CT or MRI scans, but detected on 68Ga-DOTATOC PET/CT scans. "Incidentalomas" were classified into "brain" and "body" groups based on their location. The standardized uptake values (SUVs) were compared between the two groups. A total of 61 patients with "incidentalomas" documented on the 68Ga-DOTATOC PET/CT were identified: 18 patients with 25 brain lesions and 43 patients with 85 body lesions. The mean SUV at baseline was 9.01±7.66 in the brain group and 14.8±14.63 in the body group. We present the first series on brain and body "incidentalomas" detected on 68Ga-DOTATOC PET/CT. Whole-body 68Ga-DOTATOC PET/CT may be considered in selected patients with brain tumors with high expression of somatostatin receptors to assist radiosurgical or surgical planning and, simultaneously, provide accurate follow-up with early detection of potential metastases.

Combined anti-tumor efficacy of somatostatin fusion protein and vaccinia virus on tumor cells with high expression of somatostatin receptors

Somatostatin, a growth hormone-release inhibiting peptide, exerts antiproliferative and antiangiogenic effects on tumor cells. However, the short half-life of somatostatin limits its application in human therapy, and long-acting somatostatin fusion protein is also limited by its severe terminal degradation. Therefore, oncolytic virus delivery system was introduced to express somatostatin fusion protein and the anti-tumor effects of both somatostatin and oncolytic virus were combined to destroy tumor tissues. Here, a vaccinia VG9/(SST-14)2-HSA recombinant was constructed by replacing somatostatin fusion gene into TK locus of attenuated VG9 strain via homologous recombination. Results showed that vaccinia VG9/(SST-14)2-HSA possessed a combined anti-tumor effect on sstr-positive tumor cells in vitro. In the tumor burden models, BALB/c mice with complete immunity are most suitable for evaluating tumor regression and immune activation. Complete tumor regression was observed in 3 out of 10 mice treated with vaccinia VG9/TK− or VG9/(SST-14)2-HSA, and the survival of all mice in both groups was significantly prolonged. Besides, vaccinia VG9/(SST-14)2-HSA is more effective in prolonging survival than VG9/TK−. Vaccinia VG9/(SST-14)2-HSA exerts a combined anti-tumor efficacy including the oncolytic ability provided by the virus and the anti-tumor effect contributed by (SST-14)2-HSA, which is expected to become a potent therapeutic agent for cancer treatment.

Efficacy, safety and unmet needs of evolving medical treatments for carcinoid syndrome

This review reports on the currently available medical treatment options for the control of symptoms due to carcinoid syndrome in patients with neuroendocrine tumors. The efficacy and adverse events (AEs) of approved drugs such as somatostatin analogues (SSA), telotristat ethyl (TE) and interferon-alpha, are reviewed. Somatostatin analogues remain the standard treatment of carcinoid syndrome based on the high expression of somatostatin receptors and the resulting inhibition of secretion of bioactive compounds; their use is associated with relatively mild AEs, involving mainly the gastrointestinal system, and being usually transient. Although dose escalation of SSA remains an unapproved option, it is clinically implemented to alleviate symptoms in refractory carcinoid syndrome and supported by the most recent guidelines. The side effects associated with the increased dose are in general mild and consistent with standard dose of SSA. Telotristat ethyl, an oral inhibitor of tryptophan hydroxylase, the rate-limiting enzyme in serotonin biosynthesis, represents a rather novel innovative treatment option in patients with carcinoid syndrome suffering from diarrhea and complements the standard therapy of SSA. Given the low toxicity profile, TE may be considered an early add-on treatment to SSA in patients with uncontrolled carcinoid syndrome. However, further prolonged follow-up of patients treated with TE may be needed to exclude potential AEs, such as liver toxicity or depressed mood, in patients with long-term treatment. Interferon alpha is a cytokine with direct inhibitory effect on hormone secretion and tumor cell proliferation and an approved therapy in carcinoid syndrome but is associated with significant AEs in the majority of the patients requiring frequently dose reduction. The finding of a more favorable tolerability of pegylated interferon needs to be confirmed in a prospective study.

Neuroendocrine neoplasms of the small intestine and the appendix - update of the diagnostic and therapeutic guidelines (recommended by the Polish Network of Neuroendocrine Tumours) [Nowotwory neuroendokrynne jelita cienkiego i wyrostka robaczkowego - uaktualnione zasady diagnostyki i leczenia (rekomendowane przez Polską Sieć Guzów Neuroendokrynnych)

Updated Polish recommendations for the management of patients with neuroendocrine neoplasms (NENs) of the small intestine (SINENs) and of the appendix (ANENs) are presented here. The small intestine, and especially the ileum, is one of the most common locations for these neoplasms. Most of them are well-differentiated and slow-growing tumours; uncommonly - neuroendocrine carcinomas. Their symptoms may be untypical and their diagnosis may be delayed or accidental. Najczęściej pierwszą manifestacją ANEN jest jego ostre zapalenie. Typical symptoms of carcinoid syndrome occur in approximately 20-30% of SINENs patients with distant metastases. In laboratory diagnostics the assessment of 5-hydroxyindoleacetic acid concentration is helpful in the diagnosis of carcinoid syndrome. The most commonly used imaging methods are ultrasound examination, computed tomography, magnetic resonance imaging, colonoscopy and somatostatin receptor imaging. Histopathological examination is crucial for the proper diagnosis and treatment of patients with SINENs and ANENs. The treatment of choice is a surgical procedure, either radical or palliative. Long-acting somatostatin analogues (SSAs) are essential in the medical treatment of functional and non-functional SINENs. In patients with SINENs, at the stage dissemination with progression during SSAs treatment, with high expression of somatostatin receptors, radioisotope therapy should be considered first followed by targeted therapies - everolimus. After the exhaustion of the above available therapies, chemotherapy may be considered in selected cases. Recommendations for patient monitoring are also presented.

Somatostatin analogs in patients with Zollinger Ellison syndrome (ZES): an observational study.

Zollinger Ellison syndrome (ZES) is a rare syndrome caused by gastrin hypersecretion from a gastrinoma. Gastrinoma treatment has two goals: the control of acid hypersecretion and the control of tumor growth. While therapy for the syndrome is univocally based on proton pump inhibitors, the one for disease control is still debated. We here aimed at evaluating the role of somatostatin analogs (SSAs) in the control of tumor progression in a series of ZES patients. A retrospective analysis of a prospectively collected database of ZES patients, followed and managed from 1990 to 2019, was performed. The patients' clinical, pathological, treatment, and follow-up data were analyzed. Data regarding SSAs therapy start, dosage, duration, and side effects were collected. 33 patients with ZES were diagnosed. Fourteen patients (42%) had a grade 1 (G1) neuroendocrine neoplasm (NEN), five had G2 (15%), none had G3. Fifteen patients (45%) had metastatic disease. Overall, 12 (36%) underwent SSAs therapy. The median treatment duration was 36 months. Eight patients (67%) had a sustained response to SSAs, four (33%) showed an early progression, with a significant difference in terms of PFS between the patients with early and late progression (84 vs 2 months, p = 0.004). No differences in terms of OS and PFS were observed between the treated and non-treated patients, despite the proportion of metastatic patients was greater in the SSAs-treated group (75% vs 29% in the non-treated group, p = 0.01). Present data support the use of SSAs in ZES, considering that gastrinoma is mainly a well-differentiated low-grade tumor (G1 or G2), with a high expression of somatostatin receptors.

Gastrinoma and Zollinger Ellison syndrome: A roadmap for the management between new and old therapies.

Zollinger-Ellison syndrome (ZES) associated with pancreatic or duodenal gastrinoma is characterized by gastric acid hypersecretion, which typically leads to gastroesophageal reflux disease, recurrent peptic ulcers, and chronic diarrhea. As symptoms of ZES are nonspecific and overlap with other gastrointestinal disorders, the diagnosis is often delayed with an average time between the onset of symptoms and final diagnosis longer than 5 years. The critical step for the diagnosis of ZES is represented by the initial clinical suspicion. Hypergastrinemia is the hallmark of ZES; however, hypergastrinemia might recognize several causes, which should be ruled out in order to make a final diagnosis. Gastrin levels > 1000 pg/mL and a gastric pH below 2 are considered to be diagnostic for gastrinoma; some specific tests, including esophageal pH-recording and secretin test, might be useful in selected cases, although they are not widely available. Endoscopic ultrasound is very useful for the diagnosis and the local staging of the primary tumor in patients with ZES, particularly in the setting of multiple endocrine neoplasia type 1. Some controversies about the management of these tumors also exist. For the localized stage, the combination of proton pump inhibitory therapy, which usually resolves symptoms, and surgery, whenever feasible, with curative intent represents the hallmark of gastrinoma treatment. The high expression of somatostatin receptors in gastrinomas makes them highly responsive to somatostatin analogs, supporting their use as anti-proliferative agents in patients not amenable to surgical cure. Other medical options for advanced disease are super-imposable to other neuroendocrine neoplasms, and studies specifically focused on gastrinomas only are scant and often limited to case reports or small retrospective series. The multidisciplinary approach remains the cornerstone for the proper management of this composite disease. Herein, we reviewed available literature about gastrinoma-associated ZES with a specific focus on differential diagnosis, providing potential diagnostic and therapeutic algorithms.

Two Birds with One Stone: Skull Base Meningioma and Jugulotympanic Paragangliomas with Somatostatin Receptor Positron Emission Tomography.

We describe the case of a 74-year-old female patient previously treated with radiation therapy for a meningioma of the skull base and with surgery for a right tympanic paraganglioma. After the morphological progression of the meningioma demonstrated by magnetic resonance imaging (MRI), the patient underwent somatostatin receptor positron emission tomography/computed tomography (SR-PET/CT) with Gallium-68 DOTATATE for restaging. This examination showed increased somatostatin receptor expression by the meningioma and confirmed its extension as already assessed by MRI (endocranial extension, skull base involvement and invasion of the right orbit). Furthermore, SR-PET/CT detected two small right jugulotympanic pararagangliomas with high somatostatin receptor expression. Lastly, SR-PET/CT demonstrated that this patient would be an ideal candidate for peptide receptor radionuclide therapy (PRRT) that can be used for the treatment of progressive/treatment-refractory meningiomas and relapsed paragangliomas with high somatostatin receptors expression, both conditions coexisting in this case.

Efficacy and Safety of 177Lu-DOTATATE in Lung Neuroendocrine Tumors: A Bicenter study.

The purpose of this study was to assess the efficacy and safety of 177Lu-DOTATATE in patients with somatostatin receptor (SSR)-positive lung neuroendocrine tumors (NETs). Methods: This is a retrospective review of the outcome of patients with typical carcinoid (TC) and atypical carcinoid (AC), treated with 177Lu-DOTATATE at 2 ENETS Centers of Excellence. Morphologic imaging (RECIST 1.1) and 68Ga-DOTATATE PET/CT responses were assessed at 3 mo after completion of 177Lu-DOTATATE. Concordance between 2 response assessment methods was evaluated by κ statistics. Progression-free survival (PFS) and overall survival (OS) were estimated by Kaplan-Meier analysis and compared by Log-rank test. Treatment-related adverse events (AEs) were graded based on Common Terminology Criteria for Adverse Events, version 5. Results: Of 48 patients (median age, 63 y; 13 women), 43 (90%) had AC and 5 (10%) TC. Almost all patients (47, 98%) were treated due to progression. Most patients (40, 83%) received somatostatin analogs, and 10 patients (20%) had prior everolimus, chemotherapy, or both. All patients had high SSR expression (≥ modified Krenning score 3) on pretreatment 68Ga-DOTATATE PET/CT. Patients received a median 4 (range, 1-4) cycles of 177Lu-DOTATATE (33% with concurrent radiosensitizing chemotherapy) to a median cumulative activity of 27 GBq (range, 6-43GBq). At a median follow-up of 42 mo, the median PFS and OS were 23 mo (95% CI, 18-28 mo) and 59 mo (95% CI, 50-not reached [NR]), respectively. Of 40 patients with RECIST-measurable disease and 39 patients with available 68Ga-DOTATATE PET/CT, response categories were partial response, 20% (95% CI, 10%-35%) and 44% (95% CI, 30%-59%); stable disease, 68% (95% CI, 52%-80%) and 44% (95% CI, 30%-59%); and progressive disease, 12% (95% CI, 5%-27%) by both, respectively. There was a moderate concordance between response categories by RECIST and 68Ga-DOTATATE PET/CT, weighted κ of 0.51 (95% CI, 0.21-0.68). Of patients with stable disease by RECIST, those with partial response on 68Ga-DOTATATE PET/CT had a longer OS than those with no response, NR versus 52 mo (95% CI, 28-64), hazard ratio 0.2 (95% CI, 0.1-0.6), P < 0.001. Most grade 3/4 AEs were reversible and the most common was lymphopenia (14%) with no incidence of myelodysplasia or leukemia. Conclusion: In patients with advanced progressive lung NET and satisfactory SSR expression, 177Lu-DOTATATE is effective and safe with a high disease control rate and encouraging PFS and OS.

Prospective Within-Patient Assessment of the Impact of an Unlabeled Octreotide Pre-dose on the Biodistribution and Tumor Uptake of 68Ga DOTATOC as Assessed by Dynamic Whole-body PET in Patients with Neuroendocrine Tumors: Implications for Diagnosis and Therapy.

Gastroenteropancreatic neuroendocrine tumors (GEP NETs) are often associated with high expression of somatostatin receptors (SSTRs) which allows for PET/CT imaging with radiolabeled somatostatin analogs such as 68Ga-DOTATOC. The interplay between 68Ga-DOTATOC and the synthetic somatostatin analogs commonly used to manage patient symptoms may lead to competition between the labelled and unlabeled peptides for receptor binding sites and current product labelling recommends patients be taken off somatostatin analogs before imaging. In this study, we prospectively investigated in human patients the effect of a pre-dose of octreotide, a short-acting somatostatin analog, on the distribution of 68Ga-DOTATOC in GEP NETs and normal organs. Research participants with GEP NETs were studied on two occasions using dynamic whole-body 68Ga-DOTATOC PET/CT. The two imaging studies were performed within 21 days of each other, using an identical acquisition protocol except for the administration of 50 μg of short-acting octreotide (pre-dose) immediately before the second PET/CT. Paired t-tests were used to compare tracer uptake with and without octreotide, for tumor and various normal organs. Seven participants with a mean age of 53 ± 10 years were studied. Octreotide pre-dosing decreased radiotracer uptake in the normal liver and spleen by 25 % (p = 0.04) and 47 % (p = 0.05) respectively but did not significantly change uptake in tumor (p = 0.53), red marrow (p = 0.12), kidneys (p =0.57), or pituitary gland (p = 0.27). Our data indicate SSTR imaging can be improved with a pre-dose of unlabeled octreotide given just prior to injection of the radiotracer. These data suggest there may be no need to discontinue somatostatin analog therapy prior to PET/CT with 68Ga-DOTATOC, allowing for a simpler, less disruptive patient protocol. This approach warrants further study in a variety of settings.

Feasibility and Therapeutic Potential of Combined Peptide Receptor Radionuclide Therapy With Intensive Chemotherapy for Pediatric Patients With Relapsed or Refractory Metastatic Neuroblastoma.

Recent evidence has demonstrated high expression of somatostatin receptors in neuroblastoma (NB) cells. Because of this, we endeavored to evaluate the diagnostic performance and clinical efficacy of 68Ga-DOTATATE PET/CT and peptide receptor radionuclide therapy (PRRT) using 177Lu-DOTATATE combined with chemotherapy in pediatric NB patients. In total, 14 pediatric patients with histopathologically confirmed NB underwent 68Ga-DOTATATE PET/CT. Among them, the patients who were refractory or relapsed after therapy with 131I-MIBG and had intensive uptake of 68Ga-DOTATATE were referred for PRRT using 177Lu-DOTATATE. Treatment response based on follow-up imaging was classified into complete response, partial response, stable disease, and progressive disease. After each cycle of PRRT, laboratory tests were performed for evaluation of hematological, renal, and hepatic toxicities. The CTCAE (Common Terminology Criteria for Adverse Events; version 4.03) was used for grading adverse event. Curie score and International Society of Pediatric Oncology Europe Neuroblastoma score were used for semiquantitative analysis of scans of patients who underwent PRRT. In addition, overall survival was calculated as the time interval between the date of the first cycle and the end of follow-up or death. Overall, 14 refractory NB children including 7 boys and 7 girls with a median age of 5.5 years (ranged from 4 to 9) underwent 68Ga-DOTATATE PET/CT. PET/CT was positive in 10/14 patients (71.4%), and the median number of detected lesions in positive patients was 2 (range, 1-13). Of 14 patients, 5 patients underwent PRRT, including 3 boys and 2 girls. A total of 19 PRRT cycles and 66.4 GBq 177Lu-DOTATATE were given. Among these 5 patients, 2 showed an initial complete response, which relapsed a few months later, 1 showed a partial response, and 2 showed progressive disease. According to the Kaplan-Meier test, the overall survival was estimated at 14.5 months (95% confidence interval, 8.9-20.1). In evaluation of PRRT-related toxicity according to the CTCAE, 4 patients showed grade 1, and 1 showed grade 2 leukopenia. Two patients showed grade 1, and 2 others showed grade 2 anemia. Two patients showed grade 1, and 3 patients showed grade 2 thrombocytopenia. Serum creatinine in 1 patient increased to grade 1. Combination of 177Lu-DOTATATE with chemotherapeutic agents might achieve worthwhile responses with low toxicity, encouraging survival in NB patients who have relapsed or are refractory to conventional therapy, including 131I-MIBG therapy. Imaging with 68Ga-DOTATATE PET/CT in such patients has a relatively high detection efficacy, demonstrating its potential use as an alternative imaging tool to conventional modalities such as 123I/131I-MIBG. However, further well-designed trials are highly warranted.

Peptide receptor radionuclide therapy controls inappropriate calcitriol secretion in a pancreatic neuro-endocrine tumor: a case report

BackgroundHypercalcemia of malignancy is not uncommon in patients with advanced stage cancer. In rare cases the cause of the hypercalcemia is excessive production of calcitriol, the active form of vitamin D. Although inappropriate tumoral secretion of calcitriol is typically associated with lymphomas and some ovarian germ cell tumors, we present a case of calcitriol overproduction-induced hypercalcemia due to a pancreatic neuroendocrine tumor. The high expression of somatostatin receptors on this neuroendocrine neoplasm opened up the opportunity to treat the patient with radiolabelled somatostatin analogs, which successfully controlled the refractory hypercalcaemia and calcitriol levels. This case documents a rare finding of refractory hypercalcaemia of underlying malignancy due to a calcitriol-producing pancreatic neuroendocrine tumor, responding to peptide receptor radionuclide therapy (PRRT).Case presentationA 57 years-old patient presented with back pain, general discomfort, polydipsia, polyuria, fatigue and recent weight loss of 10 kg. Clinical examination was normal and there was no relevant medical history. Biochemical evaluation showed hypercalcemia with markedly increased calcitriol levels. CT-thorax-abdomen and ultrasound guided biopsy revealed a pancreatic neuroendocrine tumor with multifocal liver metastases, suggesting that excessive overproduction of calcitriol by this neuroendocrine tumor was the cause of the refractory hypercalcemia. The patient was eligible for PRRT. Four cycles of 177Lu-DOTATATE PRRT resulted in a morphological response and a normalization of serum calcium levels, confirming the hypothesis of a calcitriol producing pancreatic neuroendocrine tumor. Progression of liver metastases warranted further therapy and temozolomide-capecitabine was started with morphological and biochemical (serum calcium, calcitriol) stabilization.ConclusionAlthough up to 30–40% of gastroenteropancreatic neuroendocrine tumors are known to be functional (i.e. producing symptoms associated with the predominant hormone/peptide secreted), calcitriol secreting pancreatic neuroendocrine tumors are very rare. However, treatment with PRRT resulted in normalization of calcium and calcitriol levels, strongly supporting the hypothesis of a calcitriol-producing pancreatic neuroendocrine tumor.

P-254 An experience of two Croatian centers in the treatment of gastroenteropancreatic neuroendocrine neoplasms with long-acting octreotide treatment

Neuroendocrine neoplasms (NENs) are a heterogeneous group of tumors whose incidence has increased steadily over the past decades. Octreotide is a somatostatin analogue which has traditionally been used for the relief of symptoms that result from the release of peptides and amines (carcinoid syndrome), although a substantial amount of evidence suggests that it has anti-proliferative effects and lengthens the time to progression of the disease. We’ve aimed to evaluate the relationship between octreotide use and progression-free survival (PFS) and overall survival (OS). Medical records of 76 patients with gastroenteropancreatic NENs treated with long-acting octreotide in the University Hospital Centre Zagreb and University Hospital Center Sisters of Charity were collected in the period from March 2011 to March 2019. A retrospective analysis was completed with the Kaplan-Meier method using the PFS and OS as a primary endpoint. Previous to octreotide treatment patients had confirmed high expression of somatostatin receptors (sst-rs) by tetroktyde scintigraphy. All patients were followed for a median of 38 months, all of them where grade 1 (27%) or grade 2 (73%). Median PFS for all patients was estimated at 12 ± 2,5 months (95% CI 9,62-14,38). Median PFS for patients with pancreatic NETs was estimated at 10 ± 0,5 months (95% CI 7,03-12,97; median Ki-67 10%), patients with NET of large intestine at 10 ± 3,67 months (95% CI 2,87-17,13; median Ki-67 14%), patients with NETs of unknown primary at 12 ± 2,6 months (95% CI 4,93-19,07; median Ki-67 6%) and for patients with NETs of small intestine at 30 ± 14,5 months (95% CI 1,57-58,48; median Ki-67 5%). Median OS was not reached in any subgroup of patients. Although overall median PFS is lower than in the PROMID study, the fact that the median OS was not reached renders long-acting octreotide as an effective treatment option with acceptable tolerability. This patient population was more heterogenous than in clinical trials and reflects the real-life setting of clinical practice.

High somatostatin receptor expression and efficacy of somatostatin analogues in patients with metastatic Merkel cell carcinoma.

Merkel cell carcinoma (MCC) is an aggressive, high-grade, cutaneous neuroendocrine tumour (NET). Agents blocking programmed death 1/programmed death ligand 1 have efficacy in metastatic MCC (mMCC), but half of patients do not derive durable benefit. Somatostatin analogues (SSAs) are commonly used to treat low- and moderate-grade NETs that express somatostatin receptors (SSTRs). To assess SSTR expression and the efficacy of SSAs in mMCC, a high-grade NET. Methods In this retrospective study of 40 patients with mMCC, SSTR expression was assessed radiologically by somatostatin receptor scintigraphy (SRS; n = 39) and/or immunohistochemically when feasible (n = 9). Nineteen patients (18 had SRS uptake in MCC tumours) were treated with SSA. Disease control was defined as progression-free survival (PFS) of ≥ 120 days after initiation of SSA. Thirty-three of 39 patients (85%) had some degree (low 52%, moderate 23%, high 10%) of SRS uptake. Of 19 patients treated with SSA, seven had a response-evaluable target lesion; three of these seven patients (43%) experienced disease control, with a median PFS of 237 days (range 152-358). Twelve of 19 patients did not have a response-evaluable lesion due to antecedent radiation; five of these 12 (42%) experienced disease control (median PFS of 429 days, range 143-1757). The degree of SSTR expression (determined by SRS and/or immunohistochemistry) did not correlate significantly with the efficacy endpoints. In contrast to other high-grade NETs, mMCC tumours appear frequently to express SSTRs. SSAs can lead to clinically meaningful disease control with minimal side-effects. Targeting of SSTRs using SSA or other novel approaches should be explored further for mMCC.

SUN-118 Somatostatin Agonist Conjugated to the Evans Blue Moiety Is a Superior Analog in the Diagnosis and Treatment of Tumors Characterized by High Somatostatin Receptor Expression

Background: Radiolabeled somatostatin (SST) analogs have been proven to be effective in the diagnosis and treatment of neuroendocrine tumors (NETs), which are characterized by high somatostatin receptor (SSTR2) expression. At present, there are several SST analogs available that differ from each other in the affinity for SSTR2 and tumor retention time. To date, only a single SST agonist -DOTA-TATE- has been approved by the FDA for imaging and treatment of NETs. Recent studies have shown that addition of Evans blue (EB) moiety to an SST agonist results in superior uptake and increased retention time within the tumors. The goal of our study was to compare the diagnostic and therapeutic efficacy of three different radiolabeled SST analogs in a tumor mice model: EB-TATE - a novel modified agonist; DOTA-TATE - an agonist and JR11 - an antagonist. Methods: A rat pancreatic cell line (AR42J), characterized by high SSTR2 expression, was used to create a subcutaneous xenograft mice model. The AR42J cells formed sizable tumors within two weeks post-injection. The 86Y-EB-TATE, 68Ga-DOTA-TATE, and 68Ga-DOTA-JR11 were used to determine standard uptake values by positron emission tomography (PET) imaging. For treatment purposes, the SST analogs were labeled with 177Lu to generate 177Lu-EB-TATE, 177Lu-DOTA-TATE and 177Lu-DOTA-JR11. The mice were assigned to treatment groups based on comparable tumor volume at baseline and received two doses (0.5mCi) of the 177Lu-labeled analogs one week apart. Tumor measurements were performed twice per week and the mice were euthanized if their tumor burden exceeded 2 cm at any point in the study or after 6 weeks - landmark of the end of the study. Results: Among the three analogs tested, the novel SST analog 86Y-EB-TATE was characterized by 4.3- and 3.7- fold higher tumor uptake in comparison to 68Ga-DOTA-TATE (p<0.001) and 68Ga-DOTA-JR11 (p<0.001), respectively. There was no significant difference between the uptake of 68Ga-DOTA-TATE and 68Ga-DOTA-JR11 (p=0.9). Consistently with higher tumor uptake on imaging, 177Lu-EB-TATE-treated mice responded to the treatment with an overall 86.5±13.2% reduction in the tumor volume after two weeks post-therapy. On the contrary, despite therapy with 177Lu-DOTA-TATE and 177Lu-DOTA-JR11, the mice treated with these agents presented with tumor progression exceeding 2 cm and were euthanized. Consequently, the progression-free survival (PFS) was significantly longer in 177Lu-EB-TATE group (24±0 days) compared with 177Lu-DOTA-TATE (7.7±2.6 days, p<0.001) and 177Lu-DOTA-JR11 (6.3±3 days, p<0.001). There was no difference in PFS between 177Lu-DOTA-TATE and 177Lu-DOTA-JR11-treated mice (p=0.3). Conclusion: EB-TATE is characterized by superior diagnostic and therapeutic efficacy in comparison to DOTA-TATE and DOTA-JR11. EB-TATE might be used as imaging and therapeutic agent in tumors characterized by high SSTR2 expression.

Pituitary Function after High-Dose 177Lu-DOTATATE Therapy and Long-Term Follow-Up

Introduction: The pituitary gland has a high expression of somatostatin receptors and is therefore a potential organ at risk for radiation-induced toxicity after ¹⁷⁷Lu-DOTATATE treatment. Objective: To study changes in pituitary function in patients with neuroendocrine tumors (NETs) treated with dosimetry-based ¹⁷⁷Lu-DOTATATE to detect possible late toxicity. Methods: 68 patients from a phase II clinical trial of dosimetry-based, individualized ¹⁷⁷Lu-DOTATATE therapy were included in this analysis. Patients had received a median of 5 (range 3–9) treatment cycles of 7.4 GBq/cycle. Median follow-up was 30 months (range 11–89). The GH/IGF-1 axis, gonadotropins, and adrenal and thyroid axes were analyzed at baseline and on a yearly basis thereafter. Percent changes in hormonal levels over time were analyzed statistically using a linear mixed model and described graphically using box plots. The absorbed radiation dose to the pituitary was estimated based on post-therapeutic imaging, and the results analyzed versus percent change in IGF-1 levels over time. Results: A statistically significant decrease in IGF-1 levels was found (p < 0.005), which correlated with the number of treatment cycles (p = 0.008) and the absorbed radiation dose (p = 0.03). A similar decrease, although non-significant, was seen in gonadotropins in postmenopausal women, while in men there was an increase during the first years after therapy, after which the levels returned to baseline. No change was observed in the adrenal or thyroid axes. Conclusions: No signs of severe endocrine disorders were detected, although a significant decrease in the GH/IGF-1 axis was found, where dosimetric analyses indicated radiation-induced damage to the pituitary gland as a probable cause.