ENETS standardized (synoptic) reporting for molecular imaging studies in neuroendocrine tumours

The European Neuroendocrine Tumor Society (ENETS) promotes practices and procedures that aim to improve the standard of care delivered to patients diagnosed with or suspected of having neuroendocrine neoplasia (NEN). At its annual Scientific Advisory Board Meeting in 2018, experts in imaging, pathology and clinical care of patients with NEN drafted guidance for the standardised reporting of diagnostic studies critical to the diagnosis, grading, staging and treatment of NEN. These included pathology, radiology, endoscopy and molecular imaging procedures. In an iterative process, a synoptic reporting template for molecular imaging procedures was developed to guide personalised therapies. Following pilot implementation and refinement within the ENETS Center of Excellence network, harmonisation with specialist imaging societies including the Society of Nuclear Medicine, European Association of Nuclear Medicine and the International Cancer Imaging Society will be pursued.

Interobserver agreement of transvaginal ultrasound and magnetic resonance imaging in local staging of cervical cancer

OBJECTIVE

To evaluate interobserver agreement for the assessment of local tumor extension in women with cervical cancer, among experienced and less experienced observers, using transvaginal ultrasound (TVS) and magnetic resonance imaging (MRI).

METHODS

The TVS observers were all gynecologists and consultant ultrasound specialists, six with and seven without previous experience in cervical cancer imaging. The MRI observers were five radiologists experienced in pelvic MRI and four less experienced radiology residents without previous experience in MRI of the pelvis. The less experienced TVS observers and all MRI observers underwent a short basic training session in the assessment of cervical tumor extension, while the experienced TVS observers received only a written directive. All observers were assigned the same images from cervical cancer patients at all stages (n = 60) and performed offline evaluation to answer the following three questions: (1) Is there a visible primary tumor? (2) Does the tumor infiltrate > ⅓ of the cervical stroma? and (3) Is there parametrial invasion? Interobserver agreement within the four groups of observers was assessed using Fleiss kappa (κ) with 95% CI.

RESULTS

Experienced and less experienced TVS observers, respectively, had moderate interobserver agreement with respect to tumor detection (κ (95% CI), 0.46 (0.40-0.53) and 0.46 (0.41-0.52)), stromal invasion > ⅓ (κ (95% CI), 0.45 (0.38-0.51) and 0.53 (0.40-0.58)) and parametrial invasion (κ (95% CI), 0.57 (0.51-0.64) and 0.44 (0.39-0.50)). Experienced MRI observers had good interobserver agreement with respect to tumor detection (κ (95% CI), 0.70 (0.62-0.78)), while less experienced MRI observers had moderate agreement (κ (95% CI), 0.51 (0.41-0.62)), and both experienced and less experienced MRI observers, respectively, had good interobserver agreement regarding stromal invasion (κ (95% CI), 0.80 (0.72-0.88) and 0.71 (0.61-0.81)) and parametrial invasion (κ (95% CI), 0.69 (0.61-0.77) and 0.71 (0.61-0.81)).

CONCLUSIONS

We found interobserver agreement for the assessment of local tumor extension in patients with cervical cancer to be moderate for TVS and moderate-to-good for MRI. The level of interobserver agreement was associated with experience among TVS observers only for parametrial invasion. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

ENETS Consensus Recommendations for the Standards of Care in Neuroendocrine Neoplasms: Follow-Up and Documentation

ENETS consensus recommendations for the standards of care in neuroendocrine neoplasms (NEN) concerning follow-up and documentation are considered in this review. The documentation of patients with NEN should include the most relevant data characterizing an individual patient from the first contact with his/her physician/hospital until his/her last presentation during follow-up. It is advocated that follow-up occurs in specialized NEN centers with regular NEN tumor boards with expert panels. The follow-up should be in accordance with the ENETS consensus guidelines from 2011 and 2016, the present and coming WHO classification and ENETS/UICC recommendations for TNM staging. The recommendations for follow-up in patients with thymic, bronchopulmonary and gastroenteropancreatic NEN are given in Table 1. However, it should be stressed that evidence-based studies for follow-up are largely missing.

Multidetector CT of pancreatic ductal adenocarcinoma: Effect of tube voltage and iodine load on tumour conspicuity and image quality

OBJECTIVES

To compare a low-tube-voltage with or without high-iodine-load multidetector CT (MDCT) protocol with a normal-tube-voltage, normal-iodine-load (standard) protocol in patients with pancreatic ductal adenocarcinoma (PDAC) with respect to tumour conspicuity and image quality.

METHODS

Thirty consecutive patients (mean age: 66 years, men/women: 14/16) preoperatively underwent triple-phase 64-channel MDCT examinations twice according to: (i) 120-kV standard protocol (PS; 0.75 g iodine (I)/kg body weight, n = 30) and (ii) 80-kV protocol A (PA; 0.75 g I/kg, n = 14) or protocol B (PB; 1 g I/kg, n = 16). Two independent readers evaluated tumour delineation and image quality blindly for all protocols. A third reader estimated the pancreas-to-tumour contrast-to-noise ratio (CNR). Statistical analysis was performed with the Chi-square test.

RESULTS

Tumour delineation was significantly better in PB and PA compared with PS (P = 0.02). The evaluation of image quality was similar for the three protocols (all, P > 0.05). The highest CNR was observed with PB and was significantly better compared to PA (P = 0.02) and PS (P = 0.0002).

CONCLUSION

In patients with PDAC, a low-tube-voltage, high-iodine-load protocol improves tumour delineation and CNR leading to higher tumour conspicuity compared to standard protocol MDCT.

KEY POINTS

• Low-tube-voltage high-iodine-load MDCT improves pancreatic cancer conspicuity compared to a standard protocol. • The pancreas-to-tumour attenuation difference increases significantly by reducing the tube voltage. • The radiation exposure dose decreases by reducing the tube voltage.

Evaluation of a new system for chest tomosynthesis: aspects of image quality of different protocols determined using an anthropomorphic phantom

OBJECTIVE

To compare the image quality obtained with the different protocols in a new chest digital tomosynthesis (DTS) system.

METHODS

A chest phantom was imaged with chest X-ray equipment with DTS. 10 protocols were used, and for each protocol, nine acquisitions were performed. Four observers visually rated the quality of the reconstructed section images according to pre-defined quality criteria in four different classes. The data were analysed with visual grading characteristics (VGC) analysis, using the vendor-recommended protocol [12-s acquisition time, source-to-image distance (SID) 180 cm] as reference, and the area under the VGC curve (AUCVGC) was determined for each protocol and class of criteria.

RESULTS

Protocols with a smaller swing angle resulted in a lower image quality for the classes of criteria "disturbance" and "homogeneity in nodule" but a higher image quality for the class "structure". The class "demarcation" showed little dependency on the swing angle. All protocols but one (6.3 s, SID 130 cm) obtained an AUCVGC significantly <0.5 (indicating lower quality than reference) for at least one class of criteria.

CONCLUSION

The study indicates that the DTS protocol with 6.3 s yields image quality similar to that obtained with the vendor-recommended protocol (12 s) but with the clinically important advantage for patients with respiratory impairment of a shorter acquisition time.

ADVANCES IN KNOWLEDGE

The study demonstrates that the image quality may be strongly affected by the choice of protocol and that the vendor-recommended protocol may not be optimal.

Computed tomography staging of pancreatic cancer: a validation study addressing interobserver agreement

BACKGROUND/OBJECTIVES

Ductal adenocarcinoma in the head of the pancreas (PDAC) is usually unresectable at the time of diagnosis due to the involvement of the peripancreatic vessels. Various preoperative classification algorithms have been developed to describe the relationship of the tumor to these vessels, but most of them lack a surgically based approach. We present a CT-based classification algorithm for PDAC based on surgical resectability principles with a focus on interobserver variability.

METHODS

Thirty patients with PDAC undergoing pancreaticoduodenectomy were examined by using a standard CT protocol. Nine radiologists, representing three different levels of expertise, evaluated the CT examinations and the tumors were classified into four categories (A-D) according to the proposed system. For the interobserver agreement, the Intraclass Correlation Coefficient (ICC) was estimated.

RESULTS

The overall ICC was 0.94 and the ICCs among the trainees, experienced radiologists, and experts were 0.85, 0.76, and 0.92, respectively. All tumors classified as category A1 showed no signs of vascular invasion at surgery. In category A2, 40% of the tumors had corresponding infiltration and required resection of the superior mesenteric vein/portal vein (SMV/PV). One of two tumors in category B2 and two of three in category C required SMV/PV resection. All six patients in category D had both arterial and venous involvement.

CONCLUSION

There is almost perfect agreement among radiologists with different levels of expertise in regards to the local staging of PDAC. For tumors in a more advanced preoperative category, an increased risk for vascular involvement was noticed at surgery.

The initial change in tumor size predicts response and survival in patients with metastatic colorectal cancer treated with combination chemotherapy

BACKGROUND

To determine whether the change in tumor diameters at the first follow-up computed tomography (CT) examination after baseline examination (first change) correlates with outcome in patients with metastatic colorectal cancer (mCRC) treated with combination chemotherapy.

PATIENTS AND METHODS

The first change was analyzed in a multicenter randomized phase III trial (Nordic VI, N = 567) comparing first-line irinotecan with either bolus or infused 5-fluorouracil. Cox proportional hazards multiple regression model and Kaplan-Meier survival analyses after correction for guarantee-time bias were carried out to evaluate correlations between first change, objective response according to RECIST 1.0, progression-free survival (PFS), and overall survival (OS).

RESULTS

The hazard ratios for PFS and OS decreased along with first change. A decrease between 10% and <30%, albeit RECIST does not regard this as a partial response, was a positive prognostic factor for PFS and OS. Patients who had new lesions or unequivocal progression of nonmeasurable lesions had a worse prognosis than those with only an increase in size of >20%.

CONCLUSIONS

The change in tumor size at the first follow-up CT is strongly prognostic for PFS and OS in mCRC.

The value of 11C-5-hydroxy-tryptophan positron emission tomography in neuroendocrine tumor diagnosis and management: experience from one center

Many neuroendocrine tumors (NET) are small and may escape localization by conventional imaging techniques. In such cases, 11C-5-hydroxy-tryptophan (11C-5-HTP) positron emission tomography (PET) has been tested as an additional diagnostic tool. Nine patients with clinically, biochemically and/or histologically confirmed NET and negative computerized tomography (CT) or magnetic resonance imaging (MRI), and 111In-pentetreotide (Octreoscan) scintigraphy underwent imaging with 11C-5-HTP-PET/CT in order to: 1) detect the primary tumor lesion in three patients; 2) detect residual disease in two patients with appendiceal carcinoid, one with rectal carcinoid, one with midgut carcinoid, and one with ectopic ACTH secretion (EAS) due to residual pulmonary carcinoid; and 3) restage a patient with medullary thyroid carcinoma (MTC) and hepatic metastases. 11C-5-HTP-PET/CT detected lesions in the mediastinum in a patient with EAS due to a pulmonary carcinoid, further hepatic metastases in a patient with carcinoid syndrome (CS) from a NET of unknown primary, further hepatic metastases in the patient with MTC, and hepatic metastases in the patient with midgut carcinoid. The 11C-5-HTP-PET/CT findings contributed to radical cure of the patient with recurrent EAS, and pointed towards bilateral adrenalectomy in the patient with EAS without evident primary tumor. In addition, 11C-5- HTP-PET/CT directed towards combined surgical and medical treatment in the patient with CS and multiple rather than single hepatic metastases and in the patient with midgut carcinoid, and towards continuation of medical treatment in the patient with MTC. 11C-5-HTP-PET/CT is a useful imaging technique, providing additional information for the diagnosis, staging and decision-making regarding management of patients with NET.

Positron emission tomography in clinical islet transplantation

The fate of islets in clinical transplantation is unclear. To elude on this positron emission tomography combined with computed tomography (PET/CT) was performed for 60 min during islet transplantation in five patients receiving six transplants. A fraction of the islets (23%) were labeled with 18F-fluorodeoxyglucose ([(18)F]FDG) and carefully mixed with unlabeled islets just prior to intraportal transplantation. The peak radioactivity concentration in the liver was found at 19 min after start of islet infusion and corresponded to only 75% of what was expected, indicating that islets are lost during the transplantation procedure. No accumulation of radioactivity was found in the lungs. A nonphysiological peak of C-peptide was found in plasma during and immediately after transplantation in all subjects. Distribution in the liver was heterogeneous with wide variations in location and concentration. Islets found in areas with concentrations of >400 IEQ/cc liver tissue varied between 1% and 32% of the graft in different subjects. No side effects attributed to the PET/CT procedure were found. Clinical outcome in all patients was comparable to that previously observed indicating that the [(18)F]FDG labeling procedure did not harm the islets. The technique has potential to be used to assess approaches to enhance islet survival and engraftment in clinical transplantation.

Long-term effects of surgical correction of adrenal hyperplasia and adenoma causing primary aldosteronism

PURPOSE

The purpose of this is to study long-time results of surgery for primary aldosteronism.

MATERIALS AND METHODS

Thirty patients operated on for primary aldosteronism were followed for an average of 7 years. All but five required potassium substitution. Systolic as well as diastolic hypertension (mean 157/93 mmHg) was present necessitating one to five antihypertensive drugs daily (mean 2.33). Preoperative indications for surgery included presumed adenoma (aldosterone-producing adenoma (APA)) or in one case unilateral dominance of hyperplasia.

RESULTS

Histopathology was classified into adenoma (n = 9), dominant nodule (n = 16), and general hyperplasia without dominating nodules (n = 5), demonstrating a higher frequency of hyperplasia than anticipated. Long-term results revealed well-controlled blood pressure (BP; mean 134/80 mmHg). Antihypertensive medication was reduced (average of 1.78 per day), but only 36% of the patients were taken off these drugs completely. S-Aldosterone was normalized. All but one (a recurrence) were normokalemic without potassium substitution at follow-up. The APA group needed less medication (median 0.5 vs. 1.5 and 2 per day) and more patients in this group were totally medication free (50%). Two recurrences occurred in the group with general hyperplasia without dominating nodules.

CONCLUSION

Nodular hyperplasia is more common than anticipated. Hypersecretion of aldosterone may be released from a large nodule identified as an adenoma, as well as from a generally hyperplastic gland that has not been identified as such. Nevertheless, surgery for lateralized disease results in good long-term control of BP with less antihypertensive medication. However, patients with dominant nodule or general hyperplasia without dominating nodules need more postoperative treatment than patients with APA. The majority of patients do not achieve normotension without medications, but they do become normokalemic.

Early prediction of response to first-line chemotherapy by sequential [18F]-2-fluoro-2-deoxy-D-glucose positron emission tomography in patients with advanced colorectal cancer

BACKGROUND

To evaluate [(18)F]-2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET), for early evaluation of response to palliative chemotherapy and for prediction of long-term outcome, in patients with metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

In a randomized trial, patients with mCRC received irinotecan-based combination chemotherapy. FDG-PET was carried out before treatment and after two cycles in 51 patients at two centers. Visual changes in tumor FDG uptake and changes measured semi-automatically, as standard uptake values (SUVs), were compared with radiological response after four and eight cycles.

RESULTS

The mean baseline SUV for all tumor lesions per patient was higher in nonresponders than in responders (mean 7.4 versus 5.6, P = 0.02). There was a strong correlation between metabolic response (changes in SUV) and objective response (r = 0.57, P = 0.00001), with a sensitivity of 77% and a specificity of 76%. There was no significant correlation between metabolic response and time to progression (P = 0.5) or overall survival (P = 0.1).

CONCLUSIONS

Although metabolic response assessed by FDG-PET reflects radiological tumor volume changes, the sensitivity and specificity are too low to support the routine use of PET in mCRC. Furthermore, PET failed to reflect long-term outcome and can, thus, not be used as surrogate end point for hard endpoint benefit.

Thioureido N-acetyllactosamine derivatives as potent galectin-7 and 9N inhibitors

Derivatives of N-acetyllactosamine carrying structurally diverse thioureido groups at galactose C3 were prepared from a C3'-azido N-acetyllactosamine derivative in a three-step reaction sequence involving azide reduction and isothiocyanate formation by thiophosgene treatment of the C3-amine, followed by reaction of the isothiocyanate with a panel of amines. Evaluation of the N-acetyllactosamine thioureas as inhibitors against galectins-1, 3, 7, 8N (N-terminal domain), and 9N (N-terminal domain) revealed thiourea-mediated affinity enhancements for galectins-1, 3, 7, and 9N. In particular, good inhibitors were discovered against galectin-7 and 9N (K(d) 23 and 47 microM, respectively, for a 3-pyridylmethylthiourea derivative), which represents more than an order of magnitude affinity enhancement over the parent natural N-acetyllactosamine.

Carbidopa pretreatment improves image interpretation and visualisation of carcinoid tumours with 11C-5-hydroxytryptophan positron emission tomography

PURPOSE

Positron emission tomography (PET) with 11C-5-hydroxytryptophan (5-HTP) as tracer is a promising imaging instrument in the management of patients with neuroendocrine tumours (NETs). However, high radioactivity concentrations in the urinary collecting system sometimes produce image reconstruction artefacts that can make detection of small NETs difficult. As a means to decrease urinary excretion of radioactivity and thereby improve image quality, we examined the effect of pretreatment with carbidopa (CD), a peripheral inhibitor of aromatic amino acid decarboxylase (AADC), which converts 5-HTP to serotonin (5-hydroxytryptamine, 5-HT).

METHODS

Six patients with midgut carcinoid metastases were examined with 11C-5-HTP PET before and 1 h after oral administration of 100 or 200 mg of CD.

RESULTS

There was a fourfold significant reduction of tracer uptake in the urinary collecting system after CD administration (p=0.0277, n=6), with a mean standard uptake value (SUV) of 155+/-195 before CD and 39+/-14 after CD. In tumour lesions there was a significant increase in SUV after CD administration (p<0. 0001, n=18), with a mean SUV of 11+/-3 before CD and 14+/-3 after CD. There was no difference between the doses (100 and 200 mg) of CD in this respect. In all patients, image interpretation and tumour detection were markedly improved after CD administration.

CONCLUSION

We conclude that CD premedication improves 11C-5-HTP PET image quality and facilitates detection of NET lesions. Because of the similarity of metabolic pathways, this method could probably be applied to improve PET imaging using other tracers like 18F-DOPA and 11C-DOPA.

Whole-body (11)C-5-hydroxytryptophan positron emission tomography as a universal imaging technique for neuroendocrine tumors: comparison with somatostatin receptor scintigraphy and computed tomography

Neuroendocrine tumors (NETs) can be small and situated almost anywhere throughout the body. Our objective was to investigate whether whole-body (WB) positron emission tomography (PET) with (11)C-5-hydroxytryptophan (5-HTP) can be used as a universal imaging technique for NETs and to compare this technique with established imaging methods. Forty-two consecutive patients with evidence of NET and a detected lesion on any conventional imaging (six bronchial, two foregut, 16 midgut, and two thymic carcinoids; one ectopic Cushing's syndrome; four gastrinomas; one insulinoma; six nonfunctioning endocrine pancreatic tumors; one gastric carcinoid, one paraganglioma; and two endocrine-differentiated pancreatic carcinomas) were studied. The WB-(11)C-5-HTP-PET examinations were compared with WB-computed tomography (CT) and somatostatin receptor scintigraphy (SRS). Tumor lesions were imaged with PET in 95% of the patients. In 58% of the patients, PET could detect more lesions than SRS and CT and equal numbers in 34%, whereas in three cases, SRS or CT showed more lesions. In 84% (16 of 19 patients), PET could visualize the primary tumor compared with 47 and 42% for SRS and CT, respectively. The surgically removed PET-positive primary tumor sizes were 6-30 mm. To conclude, this study indicates that WB-(11)C-5-HTP-PET can be used as a universal imaging method for detection of NETs. This study also shows that WB-(11)C-HTP-PET is sensitive in imaging small NET lesions, such as primary tumors, and can in a majority of cases image significantly more tumor lesions than SRS and CT.

Developments in PET for the detection of endocrine tumours

Positron emission tomography (PET) supplies a range of labelled compounds to be used for the characterization of tumour biochemistry. Some of these have proved to be of value for clinical diagnosis, treatment follow-up, and clinical research. (18)F-fluorodeoxyglucose PET scanning is now a widely accepted imaging approach in clinical oncology, reflecting increased expression of glucose transporters in cancerous tissue. This tracer, however, does not show sufficient uptake in well-differentiated tumours such as neuroendocrine tumours. Endocrine tumours have the unique characteristics of taking up and decarboxylating amine precursors. These so-called APUD characteristics offer highly specific targets for PET tracers. Using this approach, radiopharmaceuticals such as [(11)C]-5-hydroxytryptophan and [(11)C]-L-dihydroxyphenylalanine for localization of carcinoid and endocrine pancreatic tumours, 6-[(18)F]-fluorodopamine and [(11)C]-hydroxyephedrine for phaeochromocytomas, and [(11)C]-metomidate for adrenal cortical tumours have been developed. Functional imaging with PET using these compounds is now being employed to complement rather than replace other imaging modalities. Development of new PET radiopharmaceuticals may in the future allow in vivo detection of tumour biological properties, such as malignant potential and responsiveness to treatment.

Uptake of 5-fluorouracil (5-FU) in peritoneal metastases in relation to the route of drug administration and tumour debulking surgery

Patients with peritoneal metastases from colorectal cancer have a poor prognosis. Aggressive treatment by debulking surgery and intraperitoneal (i.p.) chemotherapy has been suggested as an alternative therapy. However, the drug penetrance into the tumour in relation to the administration route and surgical reduction of the tumour is not well known. We compared locoregional administration with intravenous (i.v.) injection. Thirty-four in-bred rats with peritoneal metastases were randomly allocated into eight groups and injected with 14C-labelled 5-fluorouracil (5-FU) either through the i.v. or i.p. route, with or without a preceding tumour debulking, and were sacrificed after 2 or 8 h. Tumour radioactivity was visualised by autoradiography and quantified by a computer-based image analysis. After 8 h, 19 debulked and i.p.-injected tumours had a higher drug uptake, 63.2+/-28 (mean+/-standard deviation (SD)) kBq/g than 62 native i.p.-injected tumours (32.8+/-14) or 22 debulked and i.v.-injected tumours (18.5+/-18, P=0.002). After 8 h, 9 small tumours (<median 571 pixels) which underwent i.p. injection and tumour reduction had a higher drug uptake (77.4+/-26) than 29 non-debulked and i.p.-injected (35.1+/-17) or eight debulked and i.v. injected tumours (23.0+/-16, P=0.004). For larger tumours (>/=median 571 pixels), 16 debulked and i.p.-injected tumours had a higher radioactivity (drug uptake) (150.7+/-63) at 2 h than 49 i.p.-injected native tumours (48.5+/-59) or 11 reduced and i.v.-injected tumours (19.9+/-13, P=0.03). At 8 h, 10 debulked and i.p.-injected tumours had a higher drug uptake (50.3+/-24) than 33 native and i.p.-injected (30.8+/-10) or 14 debulked and i.v.-injected tumours (16.0+/-19, P=0.001). These results indicate that a debulking procedure and locoregional treatment of peritoneal metastases is associated with an increased level of 5-FU in the tumours.

Demonstration of high monoaminoxidase-A levels in neuroendocrine gastroenteropancreatic tumors in vitro and in vivo-tumor visualization using positron emission tomography with 11C-harmine

BACKGROUND AND AIMS

A majority of neuroendocrine gastroenteropancreatic (GEP) tumors can be detected by conventional radiological methods and scintigraphic techniques. Still there are problems to visualize small tumor lesions and non-functioning tumors. The aim of this study was to investigate some of the monoamine processing pathways of neuroendocrine GEP-tumors and try to find a new tracer substance for in vivo characterization and visualization by Positron Emission Tomography (PET).

SUBJECTS AND METHODS

Autoradiography of tumor sections from 8 midgut carcinoids (MGC) and 8 endocrine pancreatic tumors (EPT) was performed with (11)C-labeled tracers for serotonin and dopamine transporters, serotonin HT2A-, dopamine D1- and muscarinic receptors and for monoamine oxidase A (MAO-A). The in vitro results initiated PET studies with (11)C-Harmine in 4 patients with MGC and 7 patients with EPT (one insulinoma, two glucagonomas and four non-functioning EPT).

RESULTS

The MAO-A-ligand Harmine expressed specific in vitro binding of 87 +/-21% for MGC and 125 +/- 50% for EPT, compared to reference tissue (rat brain, 100%). All other substances showed relatively low specific binding. (11)C-harmine-PET could visualize tumors in all patients. The mean standardized uptake value (SUV) for MGC was 7.5 +/- 3.9 and for EPT 12.9 +/- 2.7, whereas the SUV of normal liver, intestine and pancreas were 3.1 +/- 0.5, 3.4 +/- 1.2 and 8.9 +/- 3.0 respectively.

CONCLUSIONS

This study demonstrates in vitro and in vivo that neuroendocrine GEP-tumors are characterized by a high MAO-A-expression, thereby adding to the similarities of neuronal and neuroendocrine tissue. It also indicates a possible application for (11)C-harmine as a new PET-tracer for neuroendocrine GEP-tumors with the potential to visualize also non-functioning EPT's.

An unusual case of tumor thrombus in the inferior vena cava. A case report

Adrenal cortical carcinoma (ACC) is a rare malignancy. Patients present either with a functional tumor or secondary to mass effect. In non-functioning tumors, the tumor size often exceeds 5 cm by the time of diagnosis, and tumor thrombus can occur. We report on a case of a small non-functioning ACC causing a large tumor thrombus in the inferior vena cava.

An unusual case of tumor thrombus in the inferior vena cava. A case report

Adrenal cortical carcinoma (ACC) is a rare malignancy. Patients present either with a functional tumor or secondary to mass effect. In non-functioning tumors, the tumor size often exceeds 5 cm by the time of diagnosis, and tumor thrombus can occur. We report on a case of a small non-functioning ACC causing a large tumor thrombus in the inferior vena cava.

Treatment of malignant endocrine pancreatic tumors with a combination of alpha-interferon and somatostatin analogs

Somatostatin analogs and alpha-interferon induce good responses as single drugs in the treatment of endocrine pancreatic tumors. We examined the efficacy and tolerability of the combination of alpha-interferon and somatostatin analogs in 16 patients with metastatic endocrine pancreatic tumors. All patients except one had received prior treatment and were in a progressive state. Doses of alpha-interferon and somatostatin analogs were individually titrated. The alpha-interferon doses varied between 9 and 25 million units per week and were combined with 100-1500 microg of octreotide or 6000 microg of lanreotide daily. Radiological response was seen in 3 of 16 (19%) patients (median duration 23 mo). Biochemical response was seen in 10 of 16 (62.5%) patients (median duration 22 mo). All three patients previously progressing on both alpha-interferon and somatostatin analog as single drugs achieved a stabilization of the disease when treated with the combination (median duration 10 mo). Seven of eight (88%) patients previously progressing on alpha-interferon treatment benefited from the combination with biochemical partial response or stabilization. All six patients previously progressing during somatostatin analog treatment achieved biochemical partial response or stabilization. More than 80% of patients who progressed during previous treatment with either drug benefited from the combined treatment, which also was well tolerated. Thus, a combination of alpha-interferon and somatostatin analogs may be considered for patients previously progressing on treatment with alpha-interferon or somatostatin analogs. However, in this study, the value of sequential treatment has not been evaluated.

Positron emission tomography of experimental melanoma with

Positron emission tomography (PET) has evolved as a new diagnostic modality in cancer patients. Thioureylenes, such as thiouracil and methimazole, are known to be incorporated into growing melanin and selectively retained in melanotic melanoma. In the present study we used [(76)Br]5-bromo-2-thiouracil as tracer for PET imaging of human and murine melanotic melanoma transplanted subcutaneously into rats. The melanomas were clearly depicted 1 day after the injection, when [(76)Br]5-bromo-2-thiouracil was retained in the tumors though the overall radioactivity concentration in the body had declined. Accumulation of (76)Br was also seen in bladder, liver, and kidney. In addition, the rats were simultaneously injected with [(125)I]5-iodo-2-thiouracil and the tissue distribution of radioactivity was mapped by whole-body autoradiography. The results confirmed the selective uptake of thiouracil in the melanoma where the concentration of (125)I-radioactivity was about three-fold higher than that in the liver and lungs. These results show the possibility of using [(76)Br]5-bromo-2-thiouracil for PET diagnostics of melanoma, including dosimetry, prior to targeted therapy using [(131)I]5-iodo-2-thiouracil or [(211)At]5-astato-2-thiouracil.

Optimized indirect (76)Br-bromination of antibodies using N-succinimidyl para-[76Br]bromobenzoate for radioimmuno PET

Monoclonal antibody 38S1 was radiobrominated with the positron emitter (76)Br (T(1/2) = 16.2 h). Indirect labeling was performed using N-succinimidyl para-(tri-methylstannyl)benzoate (SPMB) as the precursor molecule. SPMB was labeled using Chloramine-T yielding N-succinimidyl para-[(76)Br]bromobenzoate, which was then conjugated to the antibody. Optimization of the labeling conditions and further conjugation gave a total yield ( mean+/-max error) of 49+/-2%. The immunoreactivity of the antibodies was retained after labeling. Thus, antibodies intended for positron emission tomography can be labeled with (76)Br, which gives high yields and preserved immunoreactivity when using the SPMB technique described.

[11C]Hyaluronan uptake with positron emission tomography in liver disease

BACKGROUND

A hyaluronan-loading test has been developed for assessment of hyaluronan kinetics and applied in patients with liver and joint diseases. This test describes the metabolic process of hyaluronan but cannot define the specific contribution of different organs. A method for labelling of hyaluronan with the short-lived positron-emitting radionuclide 11C has been published and in this study applied in healthy subjects and liver diseases.

MATERIALS AND METHODS

Positron emission tomography (PET) was used for the regional assessment and quantification of [11C]hyaluronan uptake in three healthy subjects, four patients with alcoholic liver cirrhosis, one with alcoholic hepatitis and one with liver steatosis. After intravenous administration of 60 MBq of 11C-labelled hyaluronan, a 55-min PET scan was performed over the liver and plasma radioactivity was analysed. Rate constants describing the transport of the [11C]hyaluronan tracer from plasma to the liver were calculated.

RESULTS

High uptake was observed in the liver combined with a rapid elimination of tracer from plasma. The liver uptake rate (k1) was significantly lower in patients (0.018 min-1) than in healthy subjects (0.043 min-1, P = 0.002). The rate constants seem to be related to the severity of the disease as defined by the Child-Pugh score.

CONCLUSIONS

The study suggests that PET with [11C]hyaluronan could be an accurate method by which to assess liver dysfunction, in conditions where endothelial cell function is impaired. The possibility of quantification over extended portions of the body also opens up possibilities to explore regional differences in liver function and to assess other elimination routes of hyaluronan.

Symptoms, signs, and functional disability in adult spondylolisthesis

STUDY DESIGN

A cross-sectional clinical study.

OBJECTIVES

To determine whether there are specific symptoms, signs, and functional disability associated with adult spondylolisthesis.

SUMMARY OF BACKGROUND DATA

In spite of the common occurrence of adult spondylolisthesis, the symptoms, signs, and disability associated with it have not been analyzed in a large, well-defined group of patients.

METHODS

The symptoms, signs, and disability of 111 consecutive patients with adult spondylolisthesis, before randomized treatment with fusion or physiotherapy, were compared with those of 39 patients with nonspecific low back pain before lumbar fusion. The patients completed a questionnaire covering clinical history and symptoms and submitted a pain drawing. The signs were documented. Functional disability and pain were quantified by 12-function and 2-pain visual analog scales, respectively.

RESULTS

Sixty-two percent of the patients reported low back pain as well as sciatica, 7% sciatica only, and 31% low back pain only. Specific signs were infrequent. A positive straight leg raising test result in 12% and an L5 sensory disturbance in 13% were the most common. The symptoms were similar in patients with spondylolisthesis and chronic low back pain, but the chronic low back pain group reported more functional disability. Patients with a nonorganic pain drawing (widespread, nonspecific pain) were more often blue collar workers; were more often and longer on sick leave; and reported reduced mental condition, sexual function, functional ability, and more pain than patients with an organic pain drawing (localized, specific pain).

CONCLUSIONS

The clinical pattern and functional disability in adult spondylolisthesis and in low back pain of nonspecific origin are similar. Sciatica in adult spondylolisthesis is typically not associated with a positive straight leg raising test result.

Use of PET in neuroendocrine tumors. In vivo applications and in vitro studies

Positron emission tomography (PET) performed with various radiolabelled compounds facilitates the study of tumor biochemistry. If the tumor uptake of an administered tracer is greater than that of surrounding normal tissue, it is also possible to localize the tumor. In initial studies, 18F-labeled deoxyglucose (FDG) was attempted to visualize the tumors, since this tracer had been successfully used in oncology, reflecting increased glucose metabolism in cancerous tissue. However, this tracer was not to any significant degree taken up by the neuroendocrine tumors. Instead, the serotonin precursor 5-hydroxytryptophan (5-HTP) labeled with 11C was used and showed an increased uptake and irreversible trapping of this tracer in carcinoid tumors. The uptake was selective and the resolution so high that we could detect more liver and lymph node metastases with PET than with CT or octreotide scintigraphy. One problem was, however, the high renal excretion of the tracer producing streaky artifacts in the area of interest. Using the decarboxylase inhibitor carbidopa, given as peroral premedication, the renal excretion decreased 6-fold and at the same time the tumor uptake increased 3-fold, hence improving the visualization of the tumors. When patients were followed during treatment with PET using 5-HTP as a tracer, a > 95% correlation between changes in urinary 5-hydroxyindoleacetic acid (U-5-HIAA) and changes in the transport rate constant for 5-HTP was observed. Thus, PET can be used to monitor treatment effects. Elevation of U-5-HIAA is considered to be uncommon in endocrine pancreatic tumors (EPTs). Initially, 11C-labeled L-DOPA was attempted as another amine important in the APUD system. With L-DOPA about half of the EPTs, mainly functioning tumors, could be detected. Recently, 5-HTP was explored as a universal tracer also for EPT and foregut carcinoids, extending the PET-examination to both thorax and abdomen (whole-body PET-examination). With this method we were able to visualize small lesions in the pancreas and thorax (e.g. ACTH-producing bronchial carcinoids) not detectable by any other method including octreotide scintigraphy, MRI and CT. Several other tracers have been investigated, e.g. the monoamineoxidase (MAO-A) inhibitor harmine with promising results in non-functioning EPTs. We are currently exploring a wide range of biochemical systems, including enzymes and receptors, both for neurotransmitters and for peptides and proteins in in vitro assays with the potential to use some of the developed tracers for in vivo visualization and tumor biological studies. In conclusion, PET is a valuable tool in the diagnosis of neuroendocrine tumors. It can detect small lesions in the thorax and abdomen not detected by other methods, which has been of great value preoperatively in several cases. It detects more lesions in the liver and lymph nodes than other methods and furthermore, it can be used to monitor treatment effects.

PET imaging of adrenal cortical tumors with the 11beta-hydroxylase tracer 11C-metomidate

The purpose of the study was to evaluate PET with the tracer 11C-metomidate as a method to identify adrenal cortical lesions.

METHODS

PET with 11C-metomidate was performed in 15 patients with unilateral adrenal mass confirmed by CT. All patients subsequently underwent surgery, except 2 who underwent biopsy only. The lesions were histopathologically examined and diagnosed as adrenal cortical adenoma (n = 6; 3 nonfunctioning), adrenocortical carcinoma (n = 2), and nodular hyperplasia (n = 1). The remaining were noncortical lesions, including 1 pheochromocytoma, 1 myelolipoma, 2 adrenal cysts, and 2 metastases.

RESULTS

All cortical lesions were easily identified because of exceedingly high uptake of 11C-metomidate, whereas the noncortical lesions showed very low uptake. High uptake was also seen in normal adrenal glands and in the stomach. The uptake was intermediate in the liver and low in other abdominal organs. Images obtained immediately after tracer injection displayed high uptake in the renal cortex and spleen. The tracer uptake in the cortical lesions increased throughout the examination. For quantitative evaluation of tracer binding in individual lesions, a model with the splenic radioactivity concentration assigned to represent nonspecific uptake was applied. Values derived with this method, however, did show the same specificity as the simpler standardized uptake value concept, with similar difference observed for cortical versus noncortical lesions.

CONCLUSION

PET with 11C-metomidate has the potential to be an attractive method for the characterization of adrenal masses with the ability to discriminate lesions of adrenal cortical origin from noncortical lesions.

Demonstration of [11C] 5-hydroxy-L-tryptophan uptake and decarboxylation in carcinoid tumors by specific positioning labeling in positron emission tomography

In three patients with carcinoid liver and/or lymph node metastases, we studied the process of tumor tracer uptake and decarboxylation by means of positron emission tomography (PET) using 5-hydroxy-L-tryptophan (5-HTP) 11C-labeled in the beta-position (HTP) and later the same day with 5-HTP 11C-labeled in the carboxyl group (HTC). With HTP, in which the 11C-label follows the molecule through decarboxylation to form 11C-serotonin, a high tumor accumulation of the tracer was found. With HTC, in which the label is rapidly eliminated from the tissues as 11CO2 if decarboxylation takes place, there was virtually no uptake by the tumors. By utilizing data from PET scanning with both tracers, we could quantify the decarboxylation rate and tissue accumulation of [11C]-serotonin and hence the enzymatic action of aromatic amino acid decarboxylase.

High yield direct 76Br-bromination of monoclonal antibodies using chloramine-T

Monoclonal antibody (MAb) A33 was labeled with the positron emitter 76Br (T(1/2) = 16.2 h). Direct labeling was done using the conventional chloramine-T method. After optimization of the labeling conditions, a maximum yield (mean +/- max error) of 77 +/- 2% was obtained at pH 6.8. In vitro binding of 76Br-A33 to SW1222 colonic cancer cells showed that the immunoreactivity was retained. Also, the MAbs 38S1 and 3S193 and the peptide hEGF were 76Br-labeled, resulting in labeling yields (mean +/- max error) of 75 +/- 3%, 63 +/- 4%, and 73 +/- 0.1%, respectively. We conclude that antibodies and peptides can be labeled conveniently with 76Br for the purpose of whole-body tumour imaging by positron emission tomography.

Effects of dextranation on the pharmacokinetics of short peptides. A PET study on mEGF

The effects of dextranation on the biodistribution of mouse epidermal growth factor (mEGF, 6 kDa) were assessed. By reductive amination, mEGF was coupled to 13 and 46 kDa dextran. The two dextranated conjugates and free mEGF were labeled with the positron-emitting nuclide (76)Br (T(1/2) = 16 h). After intravenous administration to Sprague Dawley rats, the radioactivity biodistribution was evaluated by positron emission tomography (PET) and by measurements of dissected tissues. The dextranation prolonged the retention time in blood, especially when the dextran chain was long. [(76)Br]mEGF-dextran conjugates were shown to have significantly, more than 5 times, lower kidney accumulation than the nonconjugated [(76)Br]mEGF. In conclusion, dextranation affects the biodistribution of mEGF in vivo giving a prolonged circulation time, a decreased uptake in kidney, and an increased spleen accumulation.

Positron emission tomography in neuroendocrine tumours

Positron emission tomography is an in vivo tracer and imaging technique that utilizes short-lived positron emitting radionuclides (11C, 15O, 13N, 18F) with half-lives ranging between 2 min and 2 hours. These radionuclides are interesting from the labelling viewpoint since they are natural constituents of most biologically active compounds. The short half-life is an advantage with regard to the irradiation dose to the patient but it is also a limitation since it requires the production of these radionuclides in close vicinity to the positron emission tomography camera.

Positron emission tomography and radioimmunotargeting--aspects of quantification and dosimetry

Positron emission tomography (PET) is a medical imaging tool with high resolution and good quantitative properties, which makes it suitable for in vivo quantification of radioimmunotargeting agents. Most radionuclides used in radioimmunotherapy have positron-emitting analogues, which can be used for PET imaging, and this opens the possibility of performing dosimetry with PET. These isotopes, however, often emit gamma radiation and high-energy positrons in their decay, influencing the imaging properties of PET. Spatial resolution, reconstructed background and line source recovery for a number of non-pure positron emitters were investigated and compared with the imaging properties of 18F. PET imaging properties did not degrade severely for these non-pure positron emitters, but caution has to be applied when doing quantitative measurements. To assess the possibility of conducting PET studies during therapy, by combining, for example, a small amount of 124I with 131I, the influence of the presence of large amounts of gamma radiation on PET count rate characteristics was studied. The results of these studies were related to the necessary amounts of radioactivity needed for treatment of post-operative remains of glioma. The results indicate that the count rate capabilities of 2D PET permit PET studies for dose evaluation during radioimmunotherapy.

Conjugate chemistry and cellular processing of EGF-dextran

Conjugates with specific binding to the epidermal growth factor receptor, EGFR, of interest for radionuclide based imaging and therapy were prepared using mouse epidermal growth factor, mEGF, and dextran. In one type of conjugate, mEGF was coupled to dextran by reductive amination in which the free amino group on the mEGF N-terminal reacted with the aldehyde group on the reductive end of dextran. The end-end coupled conjugate could be further activated by the cyanopyridinium agent CDAP, thereby introducing tyrosines to the dextran part. In the other type of conjugate, the cyanylating procedure using CDAP was applied, first to activate dextran and then allowing for the amino terminus of mEGF to randomly attach to the dextran. In the latter case, radionuclide-labelled tyrosines or glycines could be added in the same conjugation step. All types of mEGF-dextran conjugates had EGFR-specific binding since the binding could be displaced by an excess of non-radioactive mEGF. The conjugates were to a large extent internalized in the test cells and the associated radioactivity was retained intracellularly for different times depending on both the type of cells and conjugate applied. Different intracellular 'traffic routes' for the radionuclides are discussed as well as applications for both imaging and therapy.

Positron emission tomography and radioimmunotargeting--general aspects

To optimize radioimmunotherapy, in vivo information on individual patients, such as radionuclide uptake, kinetics, metabolic patterns and optimal administration methods, is important. An overriding problem is to determine accurately the absorbed dose in the target organ as well as critical organs. Positron Emission Tomography (PET) is a superior technique to quantify regional kinetics in vivo with a spatial resolution better than 1 cm3 and a temporal resolution better than 10 s. However, target molecules often have distribution times of several hours to days. Conventional PET nuclides are not applicable and alternative positron-emitting nuclides with matching half-lives and with suitable labelling properties are thus necessary. Over many years we have systematically developed convenient production methods and labelling techniques of suitable positron nuclides, such as 110In(T(1/2) = 1.15 h), 86Y(T(1/2) = 14 h), 76Br(T(1/2) = 16 h) and 124I(T(1/2) = 4 days). 'Dose planning' can be done, for example, with 86Y- or 124I-labelled ligands before therapy, and 90Y- and 131I-labelled analogues and double-labelling, e.g. with a 86Y/90Y-labelled ligand, can be used to determine the true radioactivity integral from a pure beta-emitting nuclide. The usefulness of these techniques was demonstrated in animal and patient studies by halogen-labelled MAbs and EGF-dextran conjugates and peptides chelated with metal ions.

Closo-dodecaborate(2-) as a linker for iodination of macromolecules. Aspects on conjugation chemistry and biodistribution

Boron-containing compounds like closo-dodecaborate(2-) are in theory suitable for radioactive labeling with halogens. The boron-halogen bond is stronger than carbon-halogen bond and is not likely to be recognized by deiodinating enzymes in vivo. Peptides and proteins may be conjugated with various closo-dodecaborate(2-)-containing ligands, and thereafter, the conjugate can be iodinated. Since closo-dodecaborate(2-) is more avidly iodinated than tyrosine in moderately acidic media, such conjugates may be directly labeled on the boron part with radioisotopes of iodine using the standard Chloramine-T procedure. Mercapto-undecahydro-closo-dodecaborate(2-) (BSH) was reacted with the double bond of allyldextran to form a boronated dextran compound of the molecular size of about 70 kDa. This compound, in the text denoted as Dx-BS, and cesium dodecahydro-closo-dodecaborate(2-) were labeled using iodine-125. The two compounds were administered to rats in order to study their in vivo stability. The results indicate that iodinated Dx-BS is stable for about 20 h in vivo. The degradation rate, as indicated by thyroid uptake, was found low. [125I]Iodo-closo-dodecaborate(2-), which is a possible degradation product of [125I]Dx-BS-I, was rapidly excreted in urine without significant accumulation in any organ.

[111In-DPTA-D-Phe1]-octreotide scintigraphy in the management of patients with advanced renal cell carcinoma

Somatostatin receptor scintigraphy using the 111In-labelled somatostatin analogue octreotide (Octreoscan) was performed in 9 patients with metastatic renal cell carcinoma. In total 11 scintigraphies were performed. Positive tumor uptakes were observed in 9 patients. The results of the octreotide scans were correlated to diagnostic CT and/or X-ray images. Forty (59%) out of 68 known tumor localizations were visualized with the octreotide scan. A second scan following therapy was performed in two patients. These patients showed progressive disease despite treatment and also exhibited intensified uptakes at octreotide scintigraphy. One false positive lesion was observed in the 40 lesions visualized in scintigraphy. It was concluded that renal cell carcinoma expresses somatostatin receptors, as could be visualized with Octreoscan scintigraphy. The scintigraphic technique can be used as an instrument for in vivo characterization of the disease. The data could also form a basis for future investigations regarding the possible therapeutic effect of octreotide in the management of renal cell cancer.

Absorption of L-DOPA from the proximal small intestine studied in the rhesus monkey by positron emission tomography

Positron emission tomography (PET) seems to be a valuable method for the understanding of intestinal absorption mechanisms, for simultaneous quantitation of absorption rate and distribution kinetics to the tissues of interest after oral drug delivery. PET was evaluated in three Rhesus monkeys for quantitation of the absorption rate from the gastrointestinal tract and the distribution kinetics into different organs. To obtain optimal standardized conditions for the measurement of absorption the drug was administered via a naso-duodenal catheter directly to the absorption site in the proximal small intestine. l-DOPA was used as study drug given in a suspension together with carbidopa and the radiomarker l-[beta-11C]DOPA. The l-DOPA suspension was given into the duodenum without and after administration of a suspension of six l-amino acids (120 mM) in order to investigate any interaction on the intestinal absorption and distribution of l-DOPA into the liver and brain tissue. Intestinal absorption was in general minor during the first study period and higher together with administered l-amino acids. The somewhat contradictory result with increased absorption when amino acids were present in the intestinal lumen, may be a consequence of increased intestinal motility initiated by the nutrient load.

Kinetics of 76Br-labeled anti-CEA antibodies in pigs; aspects of dosimetry and PET imaging properties

A monoclonal antibody labeled with the positron-emitting radionuclide 76Br (T(1/2) 16.2 h) has previously been shown useful for positron emission tomography (PET) imaging of experimental tumors. Our aim in the present study was to investigate the effects of the complex decay scheme of this radionuclide on normal organ dosimetry and PET image quality. Three mini-pigs were injected intravenously with 46-75 MBq of the 76Br-labeled anti-CEA antibody 38S1, and the whole-body kinetics followed by PET imaging for 19 h. From PET data, absorbed doses in human organs were estimated using the MIRDOSE 3.0 software. The highest 76Br concentrations were found in lungs, after a correction for the air volume in this organ. The lungs received the highest absorbed dose (mGy/MBq, mean+/-maximum error), 0.84+/-0.16, followed by liver, 0.74+/-0.28, and small intestine, 0.55+/-0.05, while the effective dose equivalent was 0.41+/-0.03 mSv/MBq. The PET imaging properties of 76Br in a two-dimensional 2D PET camera, including central area resolution and scattering effects, were investigated in phantoms and compared to those of 18F. In a 0.97 g/cm3 material, approximating soft tissue density, the FMHW ("full width at half-maximum") value of the point spread function was 7.7+/-0.2 mm for 76Br and 6.0+/-0.1 mm for 18F. In conclusion, radioimmuno PET using 76Br-labeled antibodies resulted in a fairly even distribution of the radiation dose, where the highest absorbed organ doses were only about two to three times higher than the mean absorbed body dose. The high energy beta+ spectrum in the 76Br decay had only minor effects on the resolution, but may decrease the quantification accuracy, especially in organs with a lower density such as a lung.