The joint IAEA, EANM, and SNMMI practical guidance on peptide receptor radionuclide therapy (PRRNT) in neuroendocrine tumours.

Peptide receptor radionuclide therapy (PRRNT) is a molecularly targeted radiation therapy involving the systemic administration of a radiolabelled peptide designed to target with high affinity and specificity receptors overexpressed on tumours. PRRNT employing the radiotagged somatostatin receptor agonists (90)Y-DOTATOC ([(90)Y-DOTA(0),Tyr(3)]-octreotide) or (177)Lu-DOTATATE ([(177)Lu-DOTA(0),Tyr(3),Thr(8)]-octreotide or [(177)Lu-DOTA(0),Tyr(3)]-octreotate) have been successfully used for the past 15 years to target metastatic or inoperable neuroendocrine tumours expressing the somatostatin receptor subtype 2. Accumulated evidence from clinical experience indicates that these tumours can be subjected to a high absorbed dose which leads to partial or complete objective responses in up to 30 % of treated patients. Survival analyses indicate that patients presenting with high tumour receptor expression at study entry and receiving (177)Lu-DOTATATE or (90)Y-DOTATOC treatment show significantly higher objective responses, leading to longer survival and improved quality of life. Side effects of PRRNT are typically seen in the kidneys and bone marrow. These, however, are usually mild provided adequate protective measures are undertaken. Despite the large body of evidence regarding efficacy and clinical safety, PRRNT is still considered an investigational treatment and its implementation must comply with national legislation, and ethical guidelines concerning human therapeutic investigations. This guidance was formulated based on recent literature and leading experts' opinions. It covers the rationale, indications and contraindications for PRRNT, assessment of treatment response and patient follow-up. This document is aimed at guiding nuclear medicine specialists in selecting likely candidates to receive PRRNT and to deliver the treatment in a safe and effective manner. This document is largely based on the book published through a joint international effort under the auspices of the Nuclear Medicine Section of the International Atomic Energy Agency.

Somatostatin receptor gene expression in human ocular tissues: RT-PCR and immunohistochemical study.

PURPOSE: Somatostatin (SST) analogues have been used to treat proliferative diabetic retinopathy, pseudotumor cerebri, thyroid orbitopathy, and cystoid macular edema. There is a paucity of published data in regards to cell-specific distribution of SST receptors (SSTR) in normal human eye tissues. Gene expression for all five known SSTRs in normal human ciliary body/iris, retina, choroid, and cultured retinal pigment epithelial (RPE) cells were studied. METHODS: mRNA was isolated from human ocular tissues (iris/ciliary body, retina, and choroid) dissected from eight pairs of normal eyes (9-62 years) and from RPE cells grown in culture. RT-PCR was done for all five SSTRs in all analyzed tissues. Immunohistochemistry for SSTR1 and SSTR2 was performed on eight pairs of normal human eyes (28-74 years) imbedded in paraffin. RESULTS: SSTR1 to 5 genes are expressed in retina, SSTR1 and SSTR2 genes in cultured RPE cells, and SSTR1, 2, and 4 in ciliary body and choroid. SSTR1 and SSTR2 immunoreactivity (-ir) was observed on a variety of cells within all analyzed tissues including cornea, iris, trabecular meshwork, Schlemm's canal, ciliary processes, ciliary muscle, retina, choroid, cultured RPE cells, and optic nerve. CONCLUSIONS: SSTR genes are widely expressed in normal human eye tissues, with genes for SSTR1 and SSTR2 being the most widely expressed. Genes for all SSTRs are expressed in retina. SSTR1-ir and SSTR2-ir were observed in all analyzed ocular tissues. Detailed knowledge of SSTRs distribution and function in the human eye will result in a better understanding of their role in health and disease.

Growing vascular endothelial cells express somatostatin subtype 2 receptors.

We hypothesized that non-proliferating (quiescent) human vascular endothelial cells would not express somatostatin receptor subtype 2 (sst 2) and that this receptor would be expressed when the endothelial cells begin to grow. To test this hypothesis, placental veins were harvested from 6 human placentas and 2 mm vein disks were cultured in 0.3% fibrin gels. Morphometric analysis confirmed that 50-75% of cultured vein disks developed radial capillary growth within 15 days. Sst 2 gene expression was determined by reverse transcription-polymerase chain reaction (RT-PCR) analysis of the RNA from veins before culture and from tissue-matched vein disks that exhibited an angiogenic response. The sst 2 gene was expressed in the proliferating angiogenic sprouts of human vascular endothelium. The presence of sst 2 receptors on proliferating angiogenic vessels was confirmed by immunohistochemical staining and in vivo scintigraphy. These results suggest that sst 2 may be a unique target for antiangiogenic therapy with sst 2 preferring somatostatin analogues conjugated to radioisotopes or cytotoxic agents.

Serum pancreastatin levels predict response to hepatic artery chemoembolization and somatostatin analogue therapy in metastatic neuroendocrine tumors.

INTRODUCTION: Neuroendocrine tumors often metastasize to the liver and present with disabling hormonal symptoms. Hepatic artery chemoembolization (HACE) combined with somatostatin therapy, pre-embolization, peri-embolization and post-embolization, at doses to control symptoms, is an aggressive approach that can relieve hormonal symptoms with minimal morbidity and mortality. METHODS: Chemoembolization was performed using 30 mg of adriamycin, 50 mg of mitomycin, 12 ml of hexabrix, 10 ml of ethiodol, and 360-500-microm particles. Pancreastatin, a split product of chromogranin A, was measured pre-HACE and post-HACE in all patients. RESULTS: Forty-three chemoebolization procedures were performed in 34 symptomatic patients from December 1995 to August 1999. Seventeen patients had intestinal primaries (50%), seven had pancreatic primaries (20%), five had bronchial primaries (15%), and five had unknown primaries (15%). Systemic pancreastatin levels were improved or stable in 31 patients (78%). Symptoms were improved in these 31 patients (78%). Systemic serotonin levels were improved or stable in 24 patients (60%). Radiographic improvement or stability was seen in 18 patients (45%). Procedural related morbidity included pain, fevers, nausea, vomiting, and transient elevations of liver function studies in 75-100% of patients. There was one procedural related mortality (2%). Less than 20% improvement in pancreastatin levels from baseline was associated with death in five of five patients (100%). This was not observed with serotonin levels. CONCLUSION: Measurement of serum pancreastatin levels is an easy and useful method to predict success in patients who undergo HACE plus somatostatin therapy for metastatic neuroendocrine tumors to the liver. This therapeutic approach is effective in relieving symptoms in 78% of patients, with minimal major morbidity or mortality.

Somatostatin receptor gene expression in neuroblastoma.

Somatostatin receptor expression is a favorable prognostic factor in human neuroblastoma. Somatostatin receptors have been demonstrated in vitro by pharmacologic analysis of tumor tissue and in vivo by diagnostic radioreceptor scintigraphy. However, which receptor subtypes (sst(1), sst(2), sst(3), sst(4), and sst(5)) are expressed in these tumors has not yet been delineated. We used RT-PCR to analyze expression of the five somatostatin receptor genes in 32 neuroblastoma tumor specimens. All 32 tumor specimens expressed mRNA for c-abl and sst(1); sst(2) mRNA was detected in 27/32 samples and somatostatin mRNA was detected in 30/32 tumor specimens. The remaining receptor subtypes, sst(3), sst(4), and sst(5) were variably expressed. Receptor protein for sst(1) and sst(2) was visualized in tumor neuroblasts as well as in endothelial cells of tumor vessels using immunostaining with specific anti-receptor antibodies. The effect of high expression of somatostatin receptors on cell proliferation was examined in SKNSH neuroblastoma cells transfected with sst(1) and sst(2). SS(14) binding to wild-type SKNSH cells was undetectable; but the native peptide bound with high affinity to the SKNSH/sst(1) and SKNSH/sst(2) neuroblastoma cell lines. Pharmacologic analysis of binding with two long-acting analogues, CH275 and octreotide, confirmed selective expression of sst(1) and sst(2) in stably transfected SKNSH cells. Formation of neuroblastoma xenograft tumors in nude mice was significantly delayed for both SKNSH/sst(1) (P<0.001) and SKNSH/sst(2) (P<0.05) cells compared to wild-type SKNSH. We conclude that: (1) Somatostatin receptors, sst(1) and sst(2), are expressed in the majority of neuroblastomas at diagnosis; and (2) upregulation of functional sst(1) or sst(2) in neuroblastoma cell lines suppresses tumorigenicity in a xenograft model. These observations suggest that somatostatin receptors may be a useful therapeutic target in neuroblastoma.

Desaturation function does not decline after menopause in human females.

Aging appears to decrease delta6-desaturase activity in males, but in females it is uncertain. delta6- and delta5-desaturase functions were investigated in pre- and post-menopausal women who were normoglycemic or had type 2 diabetes (2 x 2 factorial, n = 37). Subjects were compared for indicators of diabetic control, estrogen levels, fatty acid profiles and indices of delta6- and delta5-desaturase activity. Diet intakes that were compared to determine whether results were a function of dietary factors known to influence desaturase activity revealed no differences (P>0.05). Post-menopausal women with type 2 diabetes had more 18:2 n6 in serum phospholipids (P<0.05) than did the pre- and post-menopausal control subjects. Fatty acid ratios of 18:3 n6/18:2 n6 indicated greater delta6-desaturase activity for women with type 2 diabetes, but differences were not found between pre- and post-menopausal groups. Significant correlation (P < 0.05) indicates an association between diabetic status and desaturase function, but function did not appear to be affected by menopausal status. In contrast to reports using male subjects, we found no evidence that desaturase function decreased in aging females, as reported for males, or increased as hypothesized in this study.

Carcinoid syndrome caused by an atypical carcinoid of the uterine cervix.

Neuroendocrine tumors of the cervix are rare and are often under- or misdiagnosed. Because these tumors are very aggressive, early diagnosis and subsequent treatment are warranted. We describe a 46-yr-old woman with carcinoid syndrome caused by an atypical carcinoid of the uterine cervix. At age 44, she had dysplasia on Pap smear and underwent total abdominal hysterectomy with the diagnosis of adenocarcinoma. Fourteen months postoperatively, she developed the carcinoid syndrome and was found to have numerous liver metastases. Histological and immunohistochemical investigations of biopsy specimens from the patient's liver lesions and original cervical lesion ("adenocarcinoma") suggested that this woman had a primary atypical carcinoid of the uterine cervix with metastases to the liver. Treatment with octreotide and alkylating agents decreased the episodes of flushing and diarrhea within 8 weeks. If an adenocarcinoma of the uterine cervix is diagnosed, atypical carcinoid should be in the differential diagnosis. Symptoms of the carcinoid syndrome should be pursued and, if present, a urinary 5-hydroxyindolacetic acid level should be obtained. Timely diagnosis of a neuroendocrine tumor of the cervix may improve survival.

Intraoperative gamma detection of 125I-lanreotide in women with primary breast cancer.

BACKGROUND: Somatostatin receptors are present in most human breast cancers. We performed a pilot trial of intraoperative tumor-gamma detection using the radiolabeled somatostatin analog 125I-lanreotide in 13 women with 14 primary breast carcinomas. METHODS: All patients were given 125I-lanreotide intravenously before surgery. Patients underwent lumpectomy, and postresection margins were evaluated with the gamma probe. Axillary dissection specimens were evaluated ex vivo. RESULTS: Seven of 13 women had gamma probe-positive or clinically suspicious margins re-excised at the time of lumpectomy. Four of six probe-positive margins were histologically positive, and two of six probe-positive margins were histologically negative; a single clinically suspicious margin was histologically positive. A total of 270 axillary lymph nodes were evaluated ex vivo by gamma probe and histology. McNemar's contingency tests demonstrated a highly statistical correlation between histology and gamma probe counts (P < .0001). CONCLUSIONS: The overall accuracy of nodal evaluation with 125I-lanreotide/intraoperative gamma detection was 77%; the negative predictive value of this technique was 97%, however. This technique predicted the presence of tumor in 20% of axillary lymph nodes that were negative by routine histology. This technique appears safe and is able to detect positive tumor resection margins and accurately predict axillary lymph node negativity. Further trials of this technique are required to validate its utility.

Synthesis and characterization of multiply-tyrosinated, multiply-iodinated somatostatin analogs.

Radio-labeled somatostatin analogs have recently gained popularity as agents useful in intraoperative tumor localization, external scintigraphy and in situ radiotherapy. We have synthesized and characterized a series of novel N-terminally extended multiply-tyrosinated somatostatin analogs that possess high binding affinity for somatostatin receptors, exhibit biological activity comparable to the native peptide and retain these characteristics after iodination. These analogs can be radio-iodinated to high specific activities. Following radioiodination, these analogs exhibit minimal radiolysis and may be clinically useful for tumor localization, scanning and therapy.

Combination ACE inhibitor and angiotensin II receptor antagonist therapy in diabetic nephropathy.

The benefit of angiotensin-converting enzyme (ACE) inhibitor (i) therapy in diabetic glomerulosclerosis is thought to be largely the result of attenuation of angiotensin II (AngII) effects on blood pressure, glomerular hemodynamics and hypertrophy, and tissue fibrosis. The present study was undertaken to determine whether the addition of AngII receptor antagonist therapy to ACEi therapy in diabetic nephropathy results in attenuation of AngII effects beyond that achieved by ACEi therapy alone. Seven patients were studied as inpatients on the General Clinical Research Center each for 3 consecutive weeks as follows: week 1, the patients' usual regimen which included daily oral moderate to high dose ACEi therapy; week 2, the patients' usual regimen plus oral losartan (an antagonist (a) of the angiotensin type 1 receptor, AT1) 50 mg (n = 3) or 100 mg (n = 4) daily; week 3, return to the patients' usual regimen. Diet, physical activity, and blood glucose were held as constant as possible during the three weeks of daily testing. We found that plasma renin levels increased significantly during combination therapy and then returned to baseline values with discontinuation of AT1a therapy: mean baseline renin values (week 1) 3.0 ng/ml/min +/- 1.1 SE, mean renin values during combination therapy (week 2) 7.0 ng/ml/min +/- 3.2 (p = 0.0078 by Wilcoxon rank sum test), mean renin values after discontinuation of AT1a therapy (week 3) 3.9 ng/ml/min +/- 2.0 (NS compared to baseline values). In addition, 2 patients developed transient hypotension when losartan therapy was initiated. During this short-term study, 24-hour proteinuria, serum creatinine, serum potassium, and plasma aldosterone were not changed significantly by combination therapy. We conclude that in patients with diabetic nephropathy addition of AT1a therapy to ACEi therapy attenuates AngII effects better than ACEi therapy alone. We suggest that combination therapy for the management of diabetic glomerulosclerosis merits further investigation.

Multiple endocrine neoplasia type 2A: a 25-year review.

BACKGROUND/PURPOSE: Before 1970, treatment decisions for the thyroid lesions in patients with multiple endocrine neoplasia (MEN) were based on physical findings. For the next 20 years, biological markers assumed a preeminent role, and at present, DNA testing is being used to define the need for therapeutic intervention. This report presents a 25-year review of 22 children with MEN-2A, with a mean follow-up of 12.5 years. METHODS: All 22 children underwent a total thyroidectomy, and four (18%) were rendered permanently hypoparathyroid. Since 1976, however, only one patient (6.7%) has lost parathyroid function. Despite the fact that biological screening studies routinely were performed once a year in the majority of our patients and surgery was recommended for any elevation in the serum calcitonin (CT) levels, medullary carcinoma of the thyroid (MTC) developed in 17 children (77%) and only five had C cell hyperplasia (CCH). Thirteen of the 17 had macroscopic tumor described by the pathologist, evidence of recurrent disease (MTC-REC) has developed in four children (24%). RESULTS: There was considerable overlap in both the basal and stimulated CT levels among the five children with CCH, the 13 with localized MTC (MTC-NED), and the four who later had recurrent MTC. The basal calcitonin levels were between 25 and 110 (mean, 58) in the CCH patients, 30 to 1,130 (mean, 184) in the MTC-NED group, and 108 to 201 (mean, 140) in those with recurrent MTC. The corresponding stimulated calcitonin levels were 45 to 417 (mean, 179) in CCH, 111 to 9,510 (mean, 1,407) in MTC-NED, and 449 to 5,093 (mean, 3,383) in MTC-REC. CONCLUSIONS: (1) Basal and pentagastrin-stimulated CT levels did not reliably discriminate between CCH and MTC and should not be used to define the timing of thyroid surgery in children with MEN-2A. (2) Surgical therapy should be undertaken early in childhood on the basis of molecular genetic testing. (3) Postoperative complications are infrequent in the modern era.

Identification of MEN1 mutations in sporadic enteropancreatic neuroendocrine tumors by analysis of paraffin-embedded tissue.

Gastrinomas and other gastrointestinal neuroendocrine tumors may occur sporadically or as part of the inherited syndrome multiple endocrine neoplasia type 1 (MEN1). Mutations in the recently identified MEN1 gene have been described in sporadic gastrinomas and insulinomas. This study describes techniques used to identify mutations in the MEN1 gene in DNA extracted from paraffin-preserved tissue. Two novel mutations are identified in the MEN1 gene from nine archived paraffin-embedded neuroendocrine tumors, demonstrating that retrospective genetic analysis can be used to identify mutations in the MEN1 gene from preserved tissue. Conditions are provided by which paraffin-embedded tissue can be used as a source of genetic material for sequence information of sufficient quality for mutational studies of the MEN1 gene. It should also be possible to apply this retrospective genetic analysis of paraffin-embedded tissue to other disease models.

Cell trafficking, mediator release, and articular metabolism in acute inflammation of innervated or denervated isolated equine joints.

OBJECTIVES: To describe the acute cellular response, inflammatory mediator release, and effect on chondrocyte metabolism of interleukin 1 beta (IL-1 beta) in isolated innervated or denervated equine metacarpophalangeal joints. ANIMALS: One metacarpophalangeal joint of 24 adult horses. PROCEDURES: The metacarpophalangeal joint was isolated for 6 hours in a pump-perfused, auto-oxygenated, innervated or denervated metacarpophalangeal joint preparation. Isolated joints were assigned to 4 groups: control, control-denervated, inflamed, and inflamed-denervated, and inflammation was induced by intra-articular injection of IL-1 beta. Synovial fluid was collected for cytologic examination and determination of IL (IL)-1 beta, (IL-6), prostaglandin E2 (PGE2), and substance P (SP) values. Synovial membrane was immunostained with SP and nerve-specific enolase (NSE) antibodies. Cartilage was collected for determination of proteoglycan (PG) synthesis and degradation. RESULTS: IL-1 beta induced significant neutrophilic leukocytosis in synovial and synovial membrane. IL-1 beta concentration and returned to baseline by 5.5 hours, but IL-6 concentration significantly increased throughout the study. Total SP content was significantly higher in inflamed joints. There was a significant increase in 24- and 48-hour PG degradation in inflamed innervated joints. CONCLUSION: Cellular response to IL-1 beta was rapid and sustained; joint clearance of IL-1 beta was rapid, and endogenous production of IL-1 beta did not follow. The IL-6 and PGE2 concentrations significantly increased, and SP content was increased in association with inflammation but not denervation. A degradative response of cartilage of IL-1 beta was observed, and was enhanced by innervation. This model was useful for investigation of the articular response to acute inflammation and the influence of denervation in modulating this response.

Localization of ectopic corticotropin-producing carcinoid tumor with use of indium-111 pentetreotide scintigraphy.

OBJECTIVE: To report on the diagnosis of ectopic corticotropin (adrenocorticotropic hormone [ACTH])-producing bronchial carcinoid tumor by indium-111 pentetreotide (octreotide scan) scintigraphy. METHODS: We present a case of ectopic ACTH syndrome caused by an occult bronchial carcinoid tumor arising in a lymph node and review the pertinent literature. RESULTS: Biochemical diagnosis of ACTH syndrome can be difficult, and conventional imaging modalities often do not demonstrate these small carcinoid tumors. After biochemical proof of the presence of ectopic ACTH syndrome in our patient, conventional radiographic studies did not demonstrate any lesions. An octreotide scan showed a lesion in the lung, which was confirmed surgically. ACTH values returned to normal after resection of the lesion, and octreotide scans confirmed the completeness of surgical resection. The carcinoid tumor originated in a lymph node outside the bronchus. The differential diagnosis of ACTH syndrome, the localization of ectopic ACTH-producing tumors, the bronchial carcinoids, and the uniqueness of the carcinoid tumor arising in a lymph node are briefly discussed. CONCLUSION: Octreotide scintigraphy is useful in localizing occult carcinoid tumors and can be used in the follow-up of patients after successful removal of these tumors.

Intravitreal injection of octreotide acetate.

This study was conducted to determine the feasibility of injecting the somatostatin analogue, octreotide acetate (OA), into the vitreous cavity. Previous work suggests that octreotide effectively inhibits angiogenesis in vitro, thus its use in vivo may slow the progression of proliferative eye disease. Fifty micrograms of aqueous OA in 50 microliters aqueous solution was injected into the mid-vitreous of kitten eyes (n = 6), and OA levels were monitored over 4 days. A long-acting release form of octreotide (OA-LAR) was also injected into the mid-vitreous of rabbit eyes at doses of 0.36 (n = 16), 1.1 (n = 1), 2.1 (n = 1), 4.05 (n = 1), 8.2 (n = 1), and 36 mg (n = 3) in solution; and octreotide concentrations were measured at various time points over 42 days. OA concentrations were determined by a highly specific radioimmunoassay. Aqueous octreotide was eliminated rapidly (t1/2 = 16 hours) from the vitreous of the kitten eye, with only negligible amounts recoverable 4 days post-injection. In the long-acting form, OA in the rabbit eye reached peak levels at 28 days. By 42 days, OA levels had declined to the 14-day level. Doses of OA-LAR of 1.1 mg or less produced no gross evidence of clinical toxicity and elicited no grossly visible ocular side effects. Doses greater than 1.1 mg produced significant toxicity, including cataracts and rubeosis. The 28-day peak release for long-acting OA implies that monthly intravitreal injections could provide continual high levels of OA. Intravitreal injection of long-acting OA provides sustained, high concentrations of drug, and deserves further study as a potential treatment of proliferative eye diseases.

Somatostatin expression in human renal cortex and mesangial cells.

Somatostatin modulates important physiologic functions of the kidney, including mesangial cell contraction, glomerular prostaglandin synthesis, and phosphate, water and sodium excretion. In diabetic nephropathy, somatostatin inhibits renal hypertrophy. High affinity somatostatin receptors are expressed in the kidney. Circulating somatostatin concentrations, however, are generally well below the affinity constants of known somatostatin receptors. Thus, we hypothesized that somatostatin is produced in the kidney and released locally to act in an autocrine/paracrine manner. Using reverse transcriptase and polymerase chain reaction (RT-PCR) analysis, we found that fresh human renal cortex and cultured human mesangial cells express somatostatin mRNA. Restriction enzyme and Southern blot analysis confirmed that RT-PCR cDNA products were derived from somatostatin mRNA. Radioimmunoassay of mesangial cell culture supernatants demonstrated SS-immunoreactive peptide (87 +/- 30 pg/ml compared to 19 +/- 9 pg/ml in medium not exposed to cells; P < 0.05). In contrast, renal cells did not transcribe detectable levels of vasoactive intestinal peptide (VIP) or neuropeptide Y (NPY) mRNA, nor did they synthesize measurable peptide. Our results demonstrate that renal cells produce somatostatin and suggest that kidney-derived somatostatin may regulate renal function in an autocrine/paracrine manner. Characterization of this pathway may lead to novel methods to alter the course of diabetic nephropathy and other renal diseases.

Vasoactive intestinal polypeptide-secreting tumours: biology and therapy.

VIP-secreting tumours are rare, but they produce a dramatic clinical picture, the most prominent feature being profuse, watery diarrhoea and hypokalaemia. VIPomas are malignant and require sophisticated diagnostic and localization techniques in order to identify their presence. Delays in diagnosis are the rule rather than the exception. Improvements in the diagnosis of VIPomas appear to result in an increase in resectability rates. A definitive diagnosis is aided by the determination of plasma VIP concentrations through the use of sensitive radioimmunoassays. With heightened awareness of this syndrome, increasing numbers of patients can be identified and more effective treatments developed for the refractory and recurrent tumours.