Andreas K. Buck

Gene silencing by adenovirus-delivered siRNA

RNA interference is the process that double‐stranded RNA induces the homology‐dependent degradation of cognate mRNA mediated by 21–23 nucleotide short interfering RNA (siRNA). Here, we describe a simple virus vector for efficient delivery of siRNA into mammalian cells utilizing the well‐defined H1‐RNA promoter and conventional adenovirus. In this pilot study, p53 was targeted by this vector. Our results demonstrate efficient and specific knock‐down of p53 in breast cancer MCF‐7 and lung carcinoma A549 cells and indicate a prospective application of this siRNA expressing recombinant adenovirus system in functional genomics, cancer gene therapy and virus inhibition.

Initial results in the assessment of multiple myeloma using 18F-FDG PET.

Abstract. This prospective study was undertaken to investigate the appearance of multiple myeloma on fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET). Furthermore, the accuracy of FDG-PET in detecting myeloma lesions and its influence on patient management were evaluated. Forty-three patients with known multiple myeloma (n=28) or solitary plasmacytoma (n=15) underwent FDG-PET. The results of routinely performed radiographs and of scans obtained using all available imaging modalities (MRI, CT), as well as the clinical course, were used for verification of detected lesions. Focally increased tracer uptake was observed in 38 of 41 known osteolytic bone lesions (sensitivity 92.7%) in 23 patients. In addition, 71 further bone lesions which were negative on radiographs were detected in 14 patients. Twenty-six (36.6%) of these lesions could be confirmed in ten patients. As a result of FDG-PET imaging, clinical management was influenced in five (14.0%) patients. The positive predictive value for active disease was 100% in patients with focal or mixed focal/diffuse skeletal FDG uptake and 75% in patients with diffuse bone marrow uptake. Depending on the interpretation of the PET scans in patients with diffuse bone marrow uptake, the sensitivity ranged from 83.8% to 91.9% and the specificity from 83.3% to 100%. FDG-PET thus proved highly accurate in detecting multiple myeloma, and revealed a greater extent of disease than routine radiographs in 14 of 23 (60.9%) patients who had osteolytic bone lesions. FDG-PET might contribute to the initial staging of solitary plasmacytoma.

F-18 NaF PET for Detection of Bone Metastases in Lung Cancer: Accuracy, Cost-Effectiveness, and Impact on Patient Management†

As bone metastases might be present in lung cancer despite a normal bone scan, we examined various alternatives prospectively. Positron emission tomography using F‐18 sodium fluoride (PET) and single photon emission tomography (SPECT) were more sensitive than a planar bone scan. PET was more accurate with a shorter examination time than SPECT but had higher incremental costs.

Clinical relevance of imaging proliferative activity in lung nodules

PurposeRecently, the thymidine analogue 3′-deoxy-3′[18F]fluorothymidine (FLT) has been introduced for imaging proliferation with positron emission tomography (PET). In this prospective study, we examined the accuracy of FLT for differentiation of benign from malignant lung lesions and for tumour staging.MethodsA total of 47 patients with newly diagnosed pulmonary nodules on chest CT suspicious for malignancy were examined with FLT-PET in addition to routine staging procedures. A total of 43xa0patients also underwent 2-[18F]fluoro-2-deoxy-D-glucose (FDG) PET imaging. Within 2 weeks, patients underwent resective surgery or core biopsy of the pulmonary lesion.ResultsHistopathology revealed malignant lung tumours in 32 patients (20 non-small cell lung cancer, 1 small cell lung cancer, 1 pulmonary carcinoid, 1 non-Hodgkin’s lymphoma, nine metastases from extrapulmonary tumours) and benign lesions in 15 patients. Increased FLT uptake was exclusively related to malignant tumours. FLT-PET was false negative in twoxa0patients with non-small cell lung cancer, in the patient with a pulmonary carcinoid and in threexa0patients with lung metastases. The sensitivity of FLT-PET for detection of lung cancer was 90%, the specificity 100% and the accuracy 94%. Fifteen out of 21 patients with lung cancer had mediastinal lymph node metastases. FLT-PET was true positive in 7/15xa0patients, resulting in a sensitivity of 53% for N-staging (specificity 100%, accuracy 67%). Clinical TNM stage was correctly identified in 67% (20/30) patients, compared to 85% (23/27) with FDG-PET.ConclusionFLT-PET has a high specificity for the detection of malignant lung tumours. Compared with FDG, FLT-PET is less accurate for N-staging in patients with lung cancer and for detection of lung metastases. FLT-PET therefore cannot be recommended for staging of lung cancer.

[(11)C]choline PET/CT in prostate cancer patients with biochemical recurrence after radical prostatectomy.

ObjectiveTo evaluate [11C]choline positron emission tomography/computed tomography ([11C]choline PET/CT) for the detection of a biochemical recurrence of prostate cancer after radical prostatectomy.MethodsRetrospective analysis of [11C]choline PET/CT performed in 41 consecutive prostate cancer patients with a rising PSA. The mean time to biochemical relapse was 24xa0months. PSA levels were determined at time of examination, and patients received either a targeted biopsy or surgery. Histopathology reports served as reference for the evaluation of the [11C]choline PET/CT findings.ResultsMean PSA in [11C]choline PET/CT positive patients was 3.1xa0ng/ml (median 2.2xa0ng/ml, range 0.5–11.6xa0ng/ml) and 0.86xa0ng/ml in [11C]choline PET/CT negative patients (median 0.83xa0ng/ml, range 0.41–1.40xa0ng/ml). Six of 12 patients with PSAxa0<xa01.5xa0ng/ml [11C]choline PET/CT revealed a pathological uptake. Histopathology was positive in 6/12 patients in this group. At PSA levels ranging from 1.5 to 2.5xa0ng/ml all [11C]choline PET/CT were positive (nxa0=xa016), a positive histology was found in 12/16 patients (75%) and at PSA 2.5–5xa0ng/ml [11C]choline PET/CT was positive in 8/8 patients, confirmed by histology in 7/8 patients. Finally, at PSA higher than 5xa0ng/ml [11C]choline PET/CT identified 5/5 patients positive all confirmed by histology. The sensitivity of [11C]choline PET/CT for the detection of recurrence at PSAxa0<xa02.5xa0ng/ml was 89% with a positive predictive value of 72%.Conclusion[11C]choline PET/CT is useful for re-staging of prostate cancer in patients with rising PSA even at levels below 1.5xa0ng/ml. Our study confirms results from other published studies on [11C]choline PET/CT in prostate cancer relapse.

Dopaminergic dysfunction in attention deficit hyperactivity disorder (ADHD), differences between pharmacologically treated and never treated young adults : a 3,4-dihdroxy-6-[18F]fluorophenyl-l-alanine PET study

The dopaminergic system plays a key role in attention-deficit/hyperactivity disorder (ADHD). Methylphenidate (MP), a dopamine (DA) reuptake inhibitor, is a drug of first choice for treating ADHD. This cross-over study investigated alterations in DA metabolism in young males with ADHD who had never been pharmacologically treated and MP-treated patients in comparison to healthy subjects. Dynamic 3,4-dihdroxy-6-[18F]fluorophenyl-L-alanine (FDOPA) PET scans were carried out on 20 male patients with ADHD and 18 healthy men. Eight ADHD patients had never been treated with psychostimulants, the rest had received MP. Based on the tissue-slope-intercept plot parametric images of FDOPA influx rate constant (Ki) were generated for each subject from dynamic 3D FDOPA datasets and transformed into standard stereotactic space. First a volume of interest analysis was performed on each single subject. In a second step data were introduced to a SPM2 analysis to detect significant changes in mean voxel Ki values between the normal control group and each patient group. In comparison to controls, ADHD patients as a group (irrespective of treatment status) showed a lower Ki in bilateral putamen, amygdala and dorsal midbrain. There was a lower Ki in the left putamen, right amygdala and right dorsal midbrain in untreated patients compared to controls together with a relative higher influx in the left amygdala and right anterior cingulate cortex. In contrast, methylphenidate treatment was associated with a significantly lower Ki in the striatum and amygdala bilaterally, and in the right dorsal midbrain. Untreated young adult ADHD patients showed a dopamine dysfunction that might be partly due to compensatory mechanisms. MP seems to down-regulate dopamine turnover. This effect might be one component in the mechanism of action of this drug in ADHD treatment.

Clinical value of 18F-fluorodihydroxyphenylalanine positron emission tomography/computed tomography (18F-DOPA PET/CT) for detecting pheochromocytoma

PurposeIn detecting pheochromocytoma (PHEO), positron emission tomography (PET) with the radiolabelled amine precursor 18F-fluorodihydroxyphenylalanine (18F-DOPA) offers excellent specificity, while computed tomography (CT) provides high sensitivity and ability to localize lesions; therefore, the combination of these modalities could be advantageous in this setting. The aim of this study was to investigate whether combined 18F-DOPA PET/CT more accurately detects and localizes PHEO lesions than does each modality alone.Methods18F-DOPA PET, CT and 18F-DOPA PET/CT images of 25 consecutive patients undergoing diagnostic scanning of suspected sporadic or multiple endocrine neoplasia type 2 syndrome-associated PHEO were reviewed retrospectively in randomized sequence. Two blinded observers scored the images regarding the likelihood of PHEO being present and localizable. Results were correlated with subsequent clinical history and, when available, histology.ResultsOf the 19 lesions detected by all three modalities, PET identified each as positive for PHEO, but was unable to definitively localize 15 of 19 (79%). CT could definitively localize all 19 lesions, but could not definitively diagnose or exclude PHEO in 18 of 19 (95%) lesions. Furthermore, CT falsely identified as negative for PHEO one lesion which was judged to be positive for this tumor by both PET and PET/CT. Only in PET/CT scans were all 19 lesions accurately characterized and localized. On a per-patient basis, the sensitivity of 18F-DOPA PET/CT for PHEO was 100% and the specificity 88%, with a 100% positive predictive value and an 88% negative predictive value.Conclusion18F-DOPA PET/CT more accurately diagnoses and localizes adrenal and extra-adrenal masses suspicious for PHEO than do 18F-DOPA PET or CT alone.

Brain metastasis in lung cancer. Comparison of cerebral MRI and 18F-FDG-PET/CT for diagnosis in the initial staging.

UNLABELLEDnFDG-PET/CT is increasingly used in staging of lung cancer as single one stop shop method. AIM, PATIENTS, METHODS: We prospectively included 104 neurological asymptomatic patients (65 years, 26% women) with primary diagnosis of lung cancer. In all patients PET/CT including cerebral imaging and cerebral MRI were performed.nnnRESULTSnDiagnosis of brain metastases (BM) was made by PET/CT in 8 patients only (7.7%), by MRI in 22 (21.2%). In 80 patients both PET/CT and MRI showed no BM. In 6 patients (5.8%) BM were detectable on PET/CT as well as on MRI. Exclusive diagnosis of BM by MRI with negative finding on PET/CT was present in 16 patients (15.4%). 2 patients (1.9%) had findings typical for BM on PET/CT but were negative on MRI. With MRI overall 100 BM were detected, with PET/CT only 17 BM (p < 0.01). For the diagnosis of BM PET/CT showed a sensitivity of 27.3%, specificity of 97.6%, positive predictive value of 75% and negative predictive value of 83.3%. BM diameter on PET/CT and MRI were consistent in 43%, in 57% BM were measured larger on MRI.nnnDISCUSSIONnCompared to the gold standard of MRI for cerebral staging a considerable number of patients are falsely diagnosed as free from BM by PET/CT. MRI is more accurate than PET/CT for detecting multiple and smaller BM.nnnCONCLUSIONnIn patients with a curative option MRI should be performed additionally to PET/CT for definitive exclusion of brain metastases.

Performance of Integrated FDG-PET/CT for Differentiating Benign and Malignant Lung Lesions - Results from a Large Prospective Clinical Trial

PurposeThe purpose of the study was to evaluate prospectively whether integrated 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography/computed tomography (FDG-PET/CT) is more accurate for determination of malignancy in newly diagnosed pulmonary lesions compared to separate interpretation of CT and FDG-PET.ProceduresTwo hundred and seventy-six patients with newly diagnosed lung lesions underwent FDG-PET/CT. Helical CT, FDG-PET, and FDG-PET/CT were interpreted separately to determine the performance of each imaging modality. Histopathology served as reference in all patients, and in further 60 patients, a benign lesion was verified at follow-up (mean follow-up of 1,040xa0days).ResultsHistology revealed malignant lung tumors in 216 of 276 patients. With PET and PET/CT, a significantly lower number of lesions were classified as equivocal compared to CT alone (pu2009<u20090.001). Assuming that equivocal lesions are benign, performance of diagnostic tests was as follows: sensitivity, specificity, and accuracy for CT was 94, 75, and 90%, for PET 97, 83, and 94% (pu2009=u20090.021), and for PET/CT 96, 87, and 94% (pu2009=u20090.010). Assuming that equivocal lesions are malignant, sensitivity, specificity, and accuracy for CT was 99, 37, and 86%, for PET 99, 77, and 94% (pu2009<u20090.001), and for PET/CT 98, 68, and 92% (pu2009=u20090.002). PET and PET/CT showed the highest concordance (Ku2009=u20090.912; confidence interval 0.866–0.958). In lesions less than or equal to 3xa0cm, there was a significant difference in the performance of PET alone and multidetector row CT as well as PET/CT and multidetector row CT (pu2009=u20090.007), irrespective if equivocal findings were judged as malignant or benign.ConclusionFor differentiation of benign from malignant lung lesions, integrated FDG-PET/CT imaging was significantly more accurate than CT but not FDG-PET. The addition of metabolic imaging (FDG-PET) to morphological imaging (CT) leads to an increase in specificity and significantly reduced equivocal findings and is therefore recommended to further specify newly diagnosed lung lesions.

The Bone Scan in Osteomyelosclerosis

1. Hoh CK, Hawkins RA, Dahlbom M, Glaspy JA, Seegar LL, Choi Y, Schiepers CW, Huang SC, Satyamurthy N, Barrio JR, Phelps ME 1992 Whole body skeletal imaging with [F-18] fluoride ion and PET. J Comput Assist Tomogr 17:34–41. 2. Reske SN 1994 Marrow scintigraphy. In: Murray EPC, E11 PJ (eds.) Nuclear Medicine in Clinical Diagnosis and Treatment. New York, Churchill Livingstone, New York, NY, USA, pp. 705–709. Address reprint requests to: Holger Schirrmeister, M.D. Westkustenklinikum Heide Abteilung Nuklearmedizin Esmarchstr. 50 D-25746 Heide, Germany FIG. 1. An F-18 sodium fluoride PET scan was performed for highly accurate bone scintigraphy in a female patient (63 years) who suffered from backache and in whom 4 years earlier osteomyelosclerosis was diagnosed. The bone scan displayed in unusual details the skeleton and showed a very intense uptake in the lower legs, shoulders, and elbow joints. This uptake pattern was described elsewhere as nearly pathognomonic for osteomyelosclerosis. (2) Based on comparative scintigrams of the skeleton and bone marrow, the unusually detailed depiction of the skeleton was explained by thickening of the cortical bone and trabeculae and intense uptake in the joints and distal extremities because of peripheral bone marrow expansion. (2)