Patient radiation dose in percutaneous biliary interventions: recommendations for DRLs on the basis of a multicentre study

OBJECTIVE

Percutaneous biliary interventions (PBIs) can be associated with a high patient radiation dose, which can be reduced when national diagnostic reference levels (DRLs) are kept in mind. The aim of this multicentre study was to investigate patient radiation exposure in different percutaneous biliary interventions, in order to recommend national DRLs.

METHODS

A questionnaire asking for the dose area product (DAP) and the fluoroscopy time (FT) in different PBIs with ultrasound- or fluoroscopy-guided bile duct punctures was sent to 200 advanced care hospitals. Recommended national DRLs are set at the 75th percentile of all DAPs.

RESULTS

Twenty-three facilities (9 interventional radiology depts. and 14 gastroenterology depts.) returned the questionnaire (12%). Five hundred sixty-five PBIs with 19 different interventions were included in the analysis. DAPs (range 4-21,510 cGy·cm2) and FTs (range 0.07-180.33 min) varied substantially depending on the centre and type of PBI. The DAPs of initial PBIs were significantly (p < 0.0001) higher (median 2162 cGy·cm2) than those of follow-up PBIs (median 464 cGy·cm2). There was no significant difference between initial PBIs with ultrasound-guided bile duct puncture (2162 cGy·cm2) and initial PBIs with fluoroscopy-guided bile duct puncture (2132 cGy·cm2) (p = 0.85). FT varied substantially (0.07-180.33 min).

CONCLUSIONS

DAPs and FTs in percutaneous biliary interventions showed substantial variations depending on the centre and the type of PBI. PBI with US-guided bile duct puncture did not reduce DAP, when compared to PBI with fluoroscopy-guided bile duct puncture. National DRLs of 4300 cGy·cm2 for initial PBIs and 1400 cGy·cm2 for follow-up PBIs are recommended.

KEY POINTS

• DAPs and FTs in percutaneous biliary interventions showed substantial variations depending on the centre and the type of PBI. • PBI with US-guided bile duct puncture did not reduce DAP when compared to PBI with fluoroscopy-guided bile duct puncture. • DRLs of 4300 cGy·cm2for initial PBIs (establishing a transhepatic tract) and 1400 cGy·cm2for follow-up PBIs (transhepatic tract already established) are recommended.

Angiopoietin-2 drives lymphatic metastasis of pancreatic cancer

Lymphatic metastasis constitutes a critical route of disease dissemination, which limits the prognosis of patients with pancreatic ductal adenocarcinoma (PDAC). As lymphangiogenesis has been implicated in stimulation of lymphatic metastasis by vascular endothelial growth factor-C (VEGF-C) and VEGF-D, we studied the effect of the angioregulatory growth factor angiopoietin-2 (Ang-2) on PDAC progression. Ang-2 was found to be expressed in transformed cells of human PDAC specimens, with corresponding Tie-2 receptors present on blood and lymphatic endothelium. In vitro in PDAC cells, Ang-2 was subject to autocrine/paracrine TGF-β stimulation (2-fold induction, P=0.0106) acting on the -61- to +476-bp element of the human Ang-2 promoter. In turn, Ang-2 regulated the expression of genes involved in cell motility and tumor suppression. Orthotopic PDAC xenografts with forced expression of Ang-2, but not Ang-1, displayed increased blood and lymphatic vessel density, and an enhanced rate of lymphatic metastasis (6.7- to 9.1-fold, P<0.01), which was prevented by sequestration of Ang-2 via coexpression of soluble Tie-2. Notably, elevated circulating Ang-2 in patients with PDAC correlated with the extent of lymphatic metastasis. Furthermore, median survival was reduced from 28.4 to 7.7 mo in patients with circulating Ang-2 ≥ 75th percentile (P=0.0005). These findings indicate that Ang-2 participates in the control of lymphatic metastasis, constitutes a noninvasive prognostic biomarker, and may provide an accessible therapeutic target in PDAC.

Prognostic factors of long-term outcome in gastroenteropancreatic neuroendocrine tumours

Neuroendocrine tumours (NET) of the gastroenteropancreatic system comprise a malignant entity with a low incidence. Only limited information is available on long-term clinical outcome and clinically applicable prognostic factors. We performed a retrospective analysis of a large, well-characterized centre-based patient cohort of 399 patients with histologically proven NET. Data were analysed according to epidemiological, clinical and histopathological characteristics. Detailed survival analyses using the Kaplan-Meier method were performed. Prognostic factors were tested by log-rank testing and independent risk factors were analysed using a Cox regression model. In the studied cohort, primary tumours originated in the fore-, mid- and hindgut in 46.1, 37.1 and 4.5% respectively. Extra-intestinal or unknown primary tumours were present in 8.4 and 10.5% respectively. Distant metastasis was present at initial diagnosis in 69.4%. Most frequent metastatic sites were liver (85%), peritoneal cavity (18%), bones (8%), other intra-abdominal sites (6%) and lungs (4%). Overall, 5- and 10-year survival rates were 78 and 63% respectively. Time to progression after initial diagnosis was significantly shorter in pancreatic as compared with ileal NET. Survival analysis revealed significantly better clinical outcome for primary tumours smaller than 25 mm, absence of metastasis, absence of any clinical symptoms, positive immunohistochemical staining for chromogranin A and a lower Ki67 index. These results were confirmed as independent by multivariate analysis. Therefore, this large retrospective analysis of a well-documented cohort of patients with NET demonstrates several prognostic factors of clinical relevance and wide availability, which should be considered for risk stratification in the management of NET.

Health-related quality of life in patients with pancreatic cancer

BACKGROUND

Pancreatic cancer is an aggressive cancer with low survival time, with health-related quality of life (HRQoL) being of major importance. The aim of our study was to assess both generic and disease-specific HRQoL in patients with pancreatic cancer.

METHODS

Patients with pancreatic cancer were consecutively included at admission to hospital. HRQoL was determined with the disease-specific European Organization for Research and Treatment of Cancer (EORTC) and generic EuroQoL (EQ-5D) health status instruments. Scores of patients were compared to those of norm populations. The association of symptoms with overall HRQoL was analysed using linear regression.

RESULTS

A total of 45 patients with pancreatic cancer were included. The mean age was 64 years, 53% were females. Of all patients, 44% had metastases at the time of admission. HRQoL was significantly impaired for most EORTC and EQ-5D scales in comparison to norm populations. Symptoms of fatigue (-0.34 regression coefficient; 95% CI -0.63, -0.11) and pain (-0.21; 95% CI -0.39, -0.02) were significantly associated with impaired overall HRQoL.

CONCLUSIONS

HRQoL was severely impaired in patients with pancreatic cancer. Symptom control and palliative care appear to be of particular importance.

Impact of FDG-PET/MRI image fusion on the detection of pancreatic cancer

BACKGROUND

This study assessed the value of image fusion with (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET) and magnetic resonance imaging (MRI) in patients suspected of having pancreatic cancer.

METHODS

32 patients (12 women, 20 men; age 24-79 years; mean 56.6 years) were included. All patients underwent whole-body FDG-PET examinations and contrast-enhanced MRI. Image fusion used a semiautomatic voxel-based algorithm. Separate reading, side-by-side analysis and evaluation of fused PET/MRI images were performed. Results were correlated to histopathology (n = 30), or clinical follow-up (n = 2).

RESULTS

15/32 patients had pancreas cancer and 17/32 patients benign disease. The sensitivity and specificity for cancer detection by FDG-PET were 93 and 41% for visual and 86 and 58% for semiquantitative analysis whereas MRI achieved 100 and 76% respectively. Topographical assignment of PET foci by image fusion was superior to side-by-side analysis in 11/39 (28%) foci (in 8/32 patients). However, a true impact on therapeutic strategy was observed only in 1/8 patients as the presence of multiple metastases, irresectable primaries or medical reasons for inoperability prevented a curative setting.

CONCLUSION

Compared to side-by-side analysis, PET/MRI image fusion improves the anatomical assignment and interpretation of FDG foci. The therapeutic benefit for the patient however is limited in patients with multiple lesions or incurable primaries.

In vivo assessment of the gastric mucosal tolerance dose after single fraction, small volume irradiation of liver malignancies by computed tomography–guided, high-dose-rate brachytherapy

PURPOSE

The aim of this study was to assess the tolerance dose of gastric mucosa for single-fraction computed tomography (CT)-guided, high-dose-rate (HDR) brachytherapy of liver malignancies.

METHODS AND MATERIALS

A total of 33 patients treated by CT-guided HDR brachytherapy of liver malignancies in segments II and/or III were included. Dose planning was performed upon a three-dimensional CT data set acquired after percutaneous applicator positioning. All patients received gastric protection post-treatment. For further analysis, the contours of the gastric wall were defined in every CT slice using Brachyvision Software. Dose-volume histograms were calculated for each treatment and correlated with clinical data derived from questionnaires assessing Common Toxicity Criteria (CTC). All patients presenting symptoms of upper GI toxicity were examined endoscopically.

RESULTS

Summarizing all patients the minimum dose applied to 1 ml of the gastric wall (D(1 ml)) ranged from 6.3 to 34.2 Gy; median, 14.3 Gy. Toxicity was present in 18 patients (55%). We found nausea in 16 (69%), emesis in 9 (27%), cramping in 13 (39%), weight loss in 12 (36%), gastritis in 4 (12%), and ulceration in 5 patients (15%). We found a threshold dose D(1 ml) of 11 Gy for general gastric toxicity and 15.5 Gy for gastric ulceration verified by an univariate analysis (p = 0.01).

CONCLUSIONS

For a single fraction, small volume irradiation we found in the upper abdomen a threshold dose D(1 ml) of 15.5 Gy for the clinical endpoint ulceration of the gastric mucosa. This in vivo assessment is in accordance with previously published tolerance data.

Magnetic resonance imaging in the assessment of cystic pancreatic lesions: differentiation of benign and malignant lesion status

PURPOSE

To characterize cystic pancreatic lesions and tumors with magnetic resonance imaging (MRI), and to assess the value of morphological criteria in differentiating pseudocysts versus cystic tumors and benign versus malignant cystic tumors.

MATERIAL AND METHODS

Twenty-three patients with cystic pancreatic tumors or lesions underwent plain and contrast-material-enhanced MRI, including magnetic resonance cholangiopancreatography (MRCP). The MR findings were characterized and analyzed by two readers, and the role of various imaging criteria and combinations thereof for final lesion assignment were assessed. Final diagnoses were obtained from the results of open surgery (n = 19) and/or biopsy (n = 4).

RESULTS

Final diagnoses included cystic tumors (n = 11) and pseudocysts (n = 12). The lesions were located in the head (56%) and body or tail (44%). Lesion diameters ranged from 7 to 50 mm. Various lesion contrast enhancement patterns were observed for both benign and malignant lesions. Serous cystadenomas were located in the head, they were lobulated, and had wall diameters < or = 2 mm; with the combination of these characteristics all patients with serous cystadenoma could be identified, whereas in no other patient was this constellation observed.

CONCLUSION

MRI facilitated the diagnosis of serous cystadenomas, although no definite morphologic criterion for the differentiation between pseudocysts and mucinous cystadenomas was identified. In consideration of the substantial therapeutic consequences, either diagnostics in unclear cystic pancreatic lesions should comprise cyst fluid analysis if necessary, or eligible patients should be referred for surgical resection.

Direct and indirect costs in a prospective cohort of patients with pancreatic cancer

BACKGROUND

Pancreatic cancer is an aggressive cancer with a low survival time. So far, there have been no studies assessing direct and indirect costs in individual patients.

AIM

To assess prospectively the cost of illness in patients with pancreatic cancer.

METHODS

Patients were consecutively included at first admission to hospital. Sociodemographic factors, medical resource use and employment status were assessed by patient interviews and from medical records in a standardized way. Costs were calculated from the perspectives of the hospital, social insurance and society. Linear regression analyses were used to determine factors associated with costs.

RESULTS

A total of 57 patients were admitted with suspected pancreatic cancer. Of these patients, 45 (79%) had pancreatic cancer as final diagnosis, 11 (19%) pancreatitis and one patient cystadenoma. The median survival was 10.9 months in patients with pancreatic cancer. Per month of observation from societal perspective, total costs were 4075 for patients. Costs of hospitalizations were responsible for 75% of total costs. In multivariable analyses, surgery, a lower educational level, younger age, and the prevalence of metastases were significantly associated with higher total costs.

CONCLUSIONS

Costs are considerable in patients with pancreatic cancer. Our results may facilitate further economic evaluations and aid health policy-makers in resource allocation.

Magnetic resonance cholangiopancreatography: image quality, ductal morphology, and value of additional T2- and T1-weighted sequences for the assessment of suspected pancreatic cancer

PURPOSE

To assess image quality and duct morphology on magnetic resonance cholangiopancreatography (MRCP) and also the value of additional T2- and T1-weighted sequences for differentiation of benignity and malignancy in patients with suspected pancreatic tumors.

MATERIAL AND METHODS

One-hundred-and-fourteen patients received MRCP and unenhanced and contrast material-enhanced MR imaging. MR results were analyzed independently by two blinded readers, and subsequently correlated with the results from surgery, biopsy, and follow-up. Assessment included the evaluation of image quality, duct visualization and morphology, and the differentiation of pancreatic lesion status (benign versus malignant).

RESULTS

Overall, 49 patients had benign final diagnoses, while 65 had a malignant diagnosis. Image quality of single-shot thick-slab MRCP was rated significantly better than the MIP images of multisection MRCP. With MRCP alone, the two readers' accuracy in the assessment of pancreatic lesion status was 72% (95% CI, 64% to 83%) and 69% (95% CI, 56% to 77%), respectively; with the addition of T2- and T1-weighted images the accuracy significantly improved to 89% (95% CI, 82% to 95%) and 84% (95% CI, 77% to 92%) for readers 1 and 2, respectively.

CONCLUSION

Single-shot thick-slab MRCP and multisection MRCP provide complementary results; however, single-shot MRCP had superior image quality. Moreover, assessment of ductal morphology with MRCP alone facilitated the diagnosis of different pathologic conditions of the pancreatobiliary system in the majority of patients. However, with the addition of T2- and T1-weighted sequences the overall diagnostic accuracy was significantly improved and thus we consider that a comprehensive MR approach should comprise both MRCP techniques and parenchymal sequences.

Value of image fusion using single photon emission computed tomography with integrated low dose computed tomography in comparison with a retrospective voxel-based method in neuroendocrine tumours

The objective was the evaluation of single photon emission computed tomography (SPECT) with integrated low dose computed tomography (CT) in comparison with a retrospective fusion of SPECT and high-resolution CT and a side-by-side analysis for lesion localisation in patients with neuroendocrine tumours. Twenty-seven patients were examined by multidetector CT. Additionally, as part of somatostatin receptor scintigraphy (SRS), an integrated SPECT-CT was performed. SPECT and CT data were fused using software with a registration algorithm based on normalised mutual information. The reliability of the topographic assignment of lesions in SPECT-CT, retrospective fusion and side-by-side analysis was evaluated by two blinded readers. Two patients were not enrolled in the final analysis because of misregistrations in the retrospective fusion. Eighty-seven foci were included in the analysis. For the anatomical assignment of foci, SPECT-CT and retrospective fusion revealed overall accuracies of 91 and 94% (side-by-side analysis 86%). The correct identification of foci as lymph node manifestations (n=25) was more accurate by retrospective fusion (88%) than from SPECT-CT images (76%) or by side-by-side analysis (60%). Both modalities of image fusion appear to be well suited for the localisation of SRS foci and are superior to side-by-side analysis of non-fused images especially concerning lymph node manifestations.

Survival and clinical outcome of patients with neuroendocrine tumors of the gastroenteropancreatic tract in a german referral center

Neuroendocrine tumors (NETs) are rare neoplasms. Approximately 75% of all cases manifest in the gastroenteropancreatic (GEP) system. Because of the low incidence of NETs, limited data about the clinical outcome and prognostic variables are available. In an attempt to identify prognostic parameters, we investigated the distribution of primary tumors, pattern of metastasis formation, clinical presentation, histological classification, and outcome of therapeutic interventions in a large patient cohort cared for in a German referral center. In 254 patients with GEP-NETs, the primary tumor was of foregut, midgut, or hindgut origin in 44.1% (28.7% pancreas), 43.7% (34.7% jejunoileum), and 4.3%, respectively. No primary tumor was found in 7.9%. Metastases occurred preferentially in lymph nodes and the liver. The overall 5-year survival rate was 57.1%. In the absence or presence of metastases at initial diagnosis the 5-year survival rate was 80.0% and 51.7%, respectively. The 5-year survival rate was related to the localization of the primary and was 75.0% and 42.9% for jejunoileal and pancreatic tumors, respectively. The size of the primary tumor (<2 cm) and histological grading as low-grade malignant were both associated with a significantly longer survival. Surgery with curative intent was attempted in 141 patients. However, an R(0) resection was achieved in only 66.0% of these patients. Five-year survival rate in the latter group was significantly higher (77.3%) as compared with all surgical patients (55.4%). Long-term tumor-free survival was obtained in only 53.7% of successfully resected patients. Palliative medical treatment, either with chemotherapy (i.e., especially for foregut NETs) or biotherapy (especially for midgut NETs), was only moderately effective for both therapeutic regimens.

Diagnosis of neuroendocrine tumours by retrospective image fusion: is there a benefit?

This study evaluated the use of image fusion in the preoperative staging of neuroendocrine tumors (NET) of the pancreas and the gastrointestinal tract (GIT). Thirty-eight patients suffering from a metastasized NET with location of the primary in the pancreas ( n=15) or the GIT ( n=23) were examined by somatostatin receptor scintigraphy (SRS) and computed tomography (CT). Consecutive image registration and fusion were performed using custom-built software integrated in AVS/Express (Advanced Visual Systems, Waltham, MA, USA). Registration was performed by a voxel-based algorithm based on normalized mutual information. Image fusion was feasible in 36/38 patients. A total of 87 foci were assigned to anatomical regions (e.g. gut, pancreas, liver, lymph node or others) by two independent observers in both SRS and SRS/CT fusion images. The assignments used a binary ranking system (1="definite", 0="not definite"). These results were then retrospectively compared to the classification of the foci, based on postoperative histology or clinical follow-up. Imaging by SRS allowed a definite anatomical assignment in 57% (50/87) and 61% (53/87) of all lesions in the case of observers A and B, respectively. Image fusion improved the topographic assignment to 91% (79/87) and to 93% (81/87). The number classified as "definite" by both observers increased from 54% (47/87) to 86% (77/87). The increase in definite assignments was highly significant for both observers ( P<0.0001 for each). In the case of foci classified as liver metastases, image fusion allowed improved assignment to the corresponding liver segment from 45% (18/40) to 98% (39/40) and from 58% (23/40) to 100% (40/40) by observers A and B, respectively. Furthermore, the improved assignment of foci classified as lesions by image fusion was relevant for therapy in 7/36 patients (19%). Therefore, the image fusion technique presented herein appears to be a very useful method for clinical routine.

Pankreaskarzinom

Despite considerable progress in the areas of epidemiology and molecular genetics, pancreatic cancer is still characterized by a dismal prognosis. The current overview attempts a critical analysis of the published data resulting in recommendations for diagnostic and therapeutic algorithms. The diagnostic work-up of suspected pancreatic cancer patients includes an initial abdominal ultrasound which in case of ambiguous results or the absence of distant metastases is followed by "one-stop-MRI" and explorative laparotomy. Locally confined tumour disease should proceed to resective surgery which however results in cure only in a minority of resected patients even in specialized centers. Adjuvant chemotherapy might be of some benefit in terms of survival. Locally advanced but irresectable disease can be considered for combined radiochemotherapy. Systemic chemotherapy with Gemcitabine -results in marginal benefit of overall survival and may offer clinical benefit to a subgroup of patients. Best supportive care still remains the mainstay of irresectable disease. This summary highlights the urgent need for the development of innovative diagnostic and therapeutic strategies.

N34S, a pancreatitis associated SPINK1 mutation, is not associated with sporadic pancreatic cancer

BACKGROUND

The SPINK1 mutation N34S is associated to chronic pancreatitis of idiopathic, alcoholic and tropic origin. Our aim was to evaluate its prevalence in patients with sporadic pancreatic cancer.

METHODS

The N34S allele of SPINK1 was analyzed by melting curve analysis using fluorescence resonance energy transfer (FRET) probes and the LightCycler in 159 German patients with sporadic pancreatic cancer (83 male, 76 female, median age of diagnosis 61 years, range 36-84 years) and 492 healthy controls.

RESULTS

The N34S mutation was detected in 2 (1.3%) of the 159 patients with pancreatic cancer and in 8 (1.6%) of the 492 controls (not significant).

CONCLUSION

The N34S mutation of SPINK1 appears not to be a distinct genetic risk factor in patients with sporadic pancreatic cancer.

Prospective, randomized, multicenter trial on the antiproliferative effect of lanreotide, interferon alfa, and their combination for therapy of metastatic neuroendocrine gastroenteropancreatic tumors--the International Lanreotide and Interferon Alfa Study Group

PURPOSE

Somatostatin analogs and interferon alfa control hormone-active/functional neuroendocrine gastroenteropancreatic tumors. In addition to hormonal control, variable degrees of antiproliferative effects for both agents have been reported. Until now, however, no prospective, randomized studies in therapy-naive patients have compared somatostatin analogs or interferon alfa alone with a combination of the two.

METHODS

Eighty therapy-naive patients with histologically verified neuroendocrine tumor disease (primary localization: foregut, n = 36; midgut, n = 30; hindgut, n = 3; unknown, n = 11; functional, n = 29; nonfunctional, n = 51) were randomly treated either with lanreotide (1 mg three times a day administered subcutaneously [SC]) or interferon alfa (5 x 106 U three times a week SC) or both. All patients had disease progression in the 3 months before study entry, verified with imaging procedures.

RESULTS

Twenty-five patients were treated with lanreotide, 27 patients were treated with interferon alfa, and 28 patients were treated with the combination. Partial tumor remission was seen in four patients (one patient who received lanreotide, one patient who received interferon alfa, and two patients who received the combination). During the 12 months of therapy, stable disease was observed in 19 patients (seven patients who received lanreotide, seven patients who received interferon alfa, and five patients who received the combination), whereas tumor progression occurred in 14 of 25 patients (lanreotide), 15 of 27 patients (interferon alfa), and 14 of 28 patients (combination). Side effects leading to an interruption of therapy were more frequent in the combination group than in the monotherapy arms.

CONCLUSION

This prospective, randomized, multicenter study shows for the first time that somatostatin analogs, interferon alfa, or the combination of the two had comparable antiproliferative effects in the treatment of metastatic neuroendocrine gastroenteropancreatic tumors. Response rates were lower compared with those published in previous, nonrandomized studies. The antiproliferative effect of the tested substances was similar for functional and nonfunctional neuroendocrine tumors.

Prospective evaluation of pancreatic tumors: accuracy of MR imaging with MR cholangiopancreatography and MR angiography

PURPOSE

To prospectively assess accuracy of magnetic resonance (MR) imaging, MR cholangiopancreatography (MRCP), and MR angiography in patients suspected of having pancreatic tumors.

MATERIALS AND METHODS

Sixty-six patients suspected of having pancreatic tumors underwent MR imaging (unenhanced and contrast material-enhanced MR, MRCP, and contrast-enhanced MR angiography). Two blinded readers prospectively analyzed the images by consensus, and results were correlated with surgery, biopsy, or follow-up findings. Results were tabulated in two-by-two tables.

RESULTS

MR assessment of pancreatic lesion status (differentiation of benign vs malignant) resulted in 60 correct diagnoses (accuracy, 91%), and six (10%) false diagnoses. Among histologically proved malignant tumors, MR imaging yielded correct diagnoses in 42 of 44 patients (sensitivity, 95%; 95% CI: 85%, 99%), whereas 18 of 22 patients with benign findings were classified correctly. At MR imaging, findings in four patients with chronic pancreatitis were wrongly categorized as malignant tumors (specificity, 82%; 95% CI: 60%, 95%), and in one patient, a distal common bile duct carcinoma was not detected. In no patient with pancreatic adenocarcinoma was this tumor misdiagnosed as benign. In patients with malignant tumors who underwent resection, local-regional tumor growth and vascular infiltration were accurately classified in 89% and 94%, respectively. MR imaging depicted histologically proved synchronous hepatic metastases in 82%. The positive and negative predictive values for cancer nonresectability were 90% and 83%, respectively, and the accuracy, sensitivity, and specificity were 85%, 69%, and 95%, respectively.

CONCLUSION

Unenhanced and contrast-enhanced MR imaging with MRCP and MR angiography offers potential as a noninvasive tool for assessment of patients suspected of having pancreatic tumors.

Dominant negative action of an abnormal secretin receptor arising from mRNA missplicing in a gastrinoma

BACKGROUND & AIMS

The provocative secretin-stimulation test has an important role in the diagnosis and management of gastrin-secreting neuroendocrine tumors. The aim of the present study was to explore the molecular basis for positive and false-negative secretin-stimulation test results in patients with these tumors.

METHODS

One of the rare patients with this histologically proven tumor who had a normal serum gastrin level and a negative secretin-stimulation test result, and 2 more typical patients with this syndrome were investigated using immunohistochemistry, reverse-transcription polymerase chain reaction, receptor binding, and signaling assays.

RESULTS

We confirmed the molecular nature of the secretin receptor in the gastrinomas with a positive provocative test result and identified a novel mechanism for a false-negative result. Tumor expression of the class B G protein-coupled secretin receptor mediates a positive result. The false-negative result was explained by messenger RNA missplicing, resulting in a receptor variant missing exon 3 that encodes residues 44-79 in the amino-terminal tail of the mature receptor. This variant with an in-frame deletion was shown to be synthesized and to traffic to the cell surface normally, where it could neither bind secretin nor mediate a secretin-stimulated adenosine 3',5'-cyclic monophosphate response. It was able to act as a dominant negative inhibitor of wild-type secretin receptor function.

CONCLUSIONS

These data may explain some of the atypical presentations of this syndrome and provide important insights into basic mechanisms of disease.

Vasoactive intestinal peptide receptor scintigraphy in patients with pancreatic adenocarcinomas or neuroendocrine tumours

Human adenocarcinomas of the gastroenteropancreatic system overexpress vasoactive intestinal peptide (VIP) receptors and therefore represent logical diagnostic targets for receptor scintigraphy. Using iodine-123 labelled VIP, the newly employed diagnostic procedure termed VIP receptor scintigraphy (VIP-RS) appears to detect tumour tissue, especially pancreatic metastatic tumours, in almost all cases. So far, however, only a single centre has demonstrated convincing positive results. The aim of this study was to compare the sensitivity and specificity of VIP-RS with those of computer tomography (CT) and transabdominal ultrasound in patients with extensive pancreatic metastatic adenocarcinomas and neuroendocrine tumours. VIP was radiolabelled with carrier-free 123I using the chloramine T-method and preparative high-performance liquid chromatography for purification. Patients with metastatic pancreatic (n=12) and colorectal (n=3) carcinomas (adenocarcinoma: n=13, neuroendocrine tumour: n=2) were studied by VIP-RS, CT, ultrasound and, in one case, also by radioligand receptor autoradiography. Carrier-free radioiodinated VIP of maximum specific radioactivity maintained a high biological activity as determined by cAMP formation in receptor-expressing tumour cell lines. Intravenous injection of 123I-VIP did not cause any side-effects. Biodistribution, determined over 24 h, was high in the lungs and low in abdominal organs. Although all patients had extensive metastatic disease as evidenced by CT and ultrasound, VIP-RS was unable to detect either primaries or metastases in these patients. Only in two patients could a significant uptake of radiolabel be detected in organs directly infiltrated by the primary. To exclude false-negative findings, tumour tissue in one patient with a large primary, undetectable by VIP-RS, was analysed by radioligand receptor autoradiography and shown to be receptor positive. Moreover, in vitro receptor determinations showed that pancreatic carcinomas usually have fewer VIP receptors than the normal tissues to which they metastasize, like the liver. It is concluded that VIP can be radioactively labelled with maximum specific radioactivity while maintaining biological activity. Intravenous administration leads to a biodistribution almost identical to that reported previously. However, in contrast to these reports, very low sensitivity and specificity were observed for the detection of pancreatic cancers. In retrospect, these findings are not surprising since VIP receptor expression was observed to be higher in normal tissues than in neoplastic ones.

Combined imaging techniques for pancreatic cancer

Advanced pancreatic cancer has a poor prognosis. Early detection with imaging techniques can, however, improve the outlook for patients who undergo surgical resection, the only potential curative treatment. Individual techniques, however, have poor sensitivity for small masses and cannot easily differentiate tumour tissue from pancreatic masses associated with chronic pancreatitis. We combined biochemical detection on positron emission tomography with the anatomical accuracy of computed tomography and were able to improve accuracy of interpretation of imaging for patients with pancreatic cancer.

[Therapy of pancreatic adenocarcinoma]

BACKGROUND

Despite significant advances in the areas of epidemiology, risk factors, molecular genetics and diagnosis pancreatic carcinoma is characterized by a dismal prognosis and ranks 5th among malignancy-associated deaths. This article attempts to critically review the current literature and analyze therapeutic recommendations based on published evidence. Therapeutic options are based on the stage of the disease.

SURGICAL TREATMENT

Surgical resection with curative intention is feasible only in a minority of patients presenting with locally confined tumor disease. RADIO- AND CHEMOTHERAPY: Adjuvant combined radiochemotherapy might potentially improve survival and can also be considered in unresectable, locally advanced disease. The role of chemotherapy in advanced disease is exclusively palliative. Up to now, no chemotherapeutic regimen has demonstrated convincing impact on survival. Newer substances, such as gemcitabine, appear to be of some value in respect to quality of life. Best supportive care oriented at clinical symptoms remains a cornerstone in the therapeutic concept of patients with pancreatic carcinoma.

CONCLUSION

Development of innovative therapeutic strategies is therefore mandatory.

K+ channels and the intracellular calcium signal in human melanoma cell proliferation

K+ channels, membrane voltage, and intracellular free Ca2+ are involved in regulating proliferation in a human melanoma cell line (SK MEL 28). Using patch-clamp techniques, we found an inwardly rectifying K+ channel and a calcium-activated K+ channel. The inwardly rectifying K+ channel was calcium independent, insensitive to charybdotoxin, and carried the major part of the whole-cell current. The K+ channel blockers quinidine, tetraethylammonium chloride and Ba2+ and elevated extracellular K+ caused a dose-dependent membrane depolarization. This depolarization was correlated to an inhibition of cell proliferation. Charybdotoxin affected neither membrane voltage nor proliferation. Basic fibroblast growth factor and fetal calf serum induced a transient peak in intracellular Ca2+ followed by a long-lasting Ca2+ influx. Depolarization by voltage clamp decreased and hyperpolarization increased intracellular Ca2+, illustrating a transmembrane flux of Ca2+ following its electrochemical gradient. We conclude that K+ channel blockers inhibit cell-cycle progression by membrane depolarization. This in turn reduces the driving force for the influx of Ca2+, a messenger in the mitogenic signal cascade of human melanoma cells.