Experience with carbon-11 choline positron emission tomography in prostate carcinoma

We investigated the potential of carbon-11 choline positron emission tomography (PET) for the detection of lymph node and bone metastases in prostate cancer. A total of 23 patients were studied (known metastases: 8; suspicion of metastases: 3; primary staging: 12). Whole-body PET imaging was performed 5 min after injection of the tracer and completed within 1 h. Focally increased tracer uptake in bone or abdominal lymph node regions was interpreted as representing tumour involvement. All known bone and lymph node metastases could be recognized by [11C]choline PET. One out of ten negative scans for primary staging was false-negative (lymph node <1 cm) and one out of two positive scans was false-positive with regard to lymph node involvement (focal bowel activity). It is concluded that [11C]choline PET is a promising new tool for the primary staging of prostate cancer, with lymph node and bone metastases demonstrating high tracer uptake. Therapeutic management could be influenced by these results in that the technique may permit avoidance of surgical lymph node exploration.

Early detection and accurate description of extent of metastatic bone disease in breast cancer with fluoride ion and positron emission tomography

PURPOSE

Previous studies have shown that bone metastases are revealed by magnetic resonance imaging (MRI) or bone marrow scintigraphy several months before they are visible by conventional bone scintigraphy (BS). We present a new approach for detecting bone metastases in patients with breast cancer. We compared findings obtained with fluoride ion (F-18) and positron emission tomography (PET) with those obtained with conventional BS.

PATIENTS AND METHODS

Thirty-four breast cancer patients were prospectively examined using F-18-PET and conventional BS. F-18-PET and BS were performed within 3 weeks of each other. Metastatic bone disease was previously known to be present in six patients and was suspected (bone pain or increasing levels of tumor markers, Ca(2+), alkaline phosphatase) in 28 patients. Both imaging modalities were compared by patient-by-patient analysis and lesion-by-lesion analysis, using a five-point scale for receiver operating characteristic (ROC) curve analysis. A panel of reference methods was used, including MRI (28 patients), planar x-ray (17 patients), and spiral computed tomography (four patients).

RESULTS

With F-18-PET, 64 bone metastases were detected in 17 patients. Only 29 metastases were detected in 11 patients with BS. As a result of F-18-PET imaging, clinical management was changed in four patients (11.7%). For F-18-PET, the area under the ROC curve was 0.99 on a lesion basis (for BS, it was 0.74; P <.05) and 1.00 on a patient basis (for BS, it was 0.82; P <.05).

CONCLUSION

F-18-PET demonstrates a very early bone reaction when small bone marrow metastases are present, allowing accurate detection of breast cancer bone metastases. This accurate detection has a significant effect on clinical management, compared with the effect on management brought about by detection with conventional BS.

Tumor VEGF:VEGFR2 autocrine feed-forward loop triggers angiogenesis in lung cancer

The molecular mechanisms that control the balance between antiangiogenic and proangiogenic factors and initiate the angiogenic switch in tumors remain poorly defined. By combining chemical genetics with multimodal imaging, we have identified an autocrine feed-forward loop in tumor cells in which tumor-derived VEGF stimulates VEGF production via VEGFR2-dependent activation of mTOR, substantially amplifying the initial proangiogenic signal. Disruption of this feed-forward loop by chemical perturbation or knockdown of VEGFR2 in tumor cells dramatically inhibited production of VEGF in vitro and in vivo. This disruption was sufficient to prevent tumor growth in vivo. In patients with lung cancer, we found that this VEGF:VEGFR2 feed-forward loop was active, as the level of VEGF/VEGFR2 binding in tumor cells was highly correlated to tumor angiogenesis. We further demonstrated that inhibition of tumor cell VEGFR2 induces feedback activation of the IRS/MAPK signaling cascade. Most strikingly, combined pharmacological inhibition of VEGFR2 (ZD6474) and MEK (PD0325901) in tumor cells resulted in dramatic tumor shrinkage, whereas monotherapy only modestly slowed tumor growth. Thus, a tumor cell-autonomous VEGF:VEGFR2 feed-forward loop provides signal amplification required for the establishment of fully angiogenic tumors in lung cancer. Interrupting this feed-forward loop switches tumor cells from an angiogenic to a proliferative phenotype that sensitizes tumor cells to MAPK inhibition.

Assessment of 18F-PI-2620 as a Biomarker in Progressive Supranuclear Palsy

Importance

Progressive supranuclear palsy (PSP) is a 4-repeat tauopathy. Region-specific tau aggregates establish the neuropathologic diagnosis of definite PSP post mortem. Future interventional trials against tau in PSP would strongly benefit from biomarkers that support diagnosis.

Objective

To investigate the potential of the novel tau radiotracer 18F-PI-2620 as a biomarker in patients with clinically diagnosed PSP.

Design, Setting, and Participants

In this cross-sectional study, participants underwent dynamic 18F-PI-2620 positron emission tomography (PET) from 0 to 60 minutes after injection at 5 different centers (3 in Germany, 1 in the US, and 1 in Australia). Patients with PSP (including those with Richardson syndrome [RS]) according to Movement Disorder Society PSP criteria were examined together with healthy controls and controls with disease. Four additionally referred individuals with PSP-RS and 2 with PSP-non-RS were excluded from final data analysis owing to incomplete dynamic PET scans. Data were collected from December 2016 to October 2019 and were analyzed from December 2018 to December 2019.

Main Outcomes and Measures

Postmortem autoradiography was performed in independent PSP-RS and healthy control samples. By in vivo PET imaging, 18F-PI-2620 distribution volume ratios were obtained in globus pallidus internus and externus, putamen, subthalamic nucleus, substantia nigra, dorsal midbrain, dentate nucleus, dorsolateral, and medial prefrontal cortex. PET data were compared between patients with PSP and control groups and were corrected for center, age, and sex.

Results

Of 60 patients with PSP, 40 (66.7%) had RS (22 men [55.0%]; mean [SD] age, 71 [6] years; mean [SD] PSP rating scale score, 38 [15]; score range, 13-71) and 20 (33.3%) had PSP-non-RS (11 men [55.0%]; mean [SD] age, 71 [9] years; mean [SD] PSP rating scale score, 24 [11]; score range, 11-41). Ten healthy controls (2 men; mean [SD] age, 67 [7] years) and 20 controls with disease (of 10 [50.0%] with Parkinson disease and multiple system atrophy, 7 were men; mean [SD] age, 61 [8] years; of 10 [50.0%] with Alzheimer disease, 5 were men; mean [SD] age, 69 [10] years). Postmortem autoradiography showed blockable 18F-PI-2620 binding in patients with PSP and no binding in healthy controls. The in vivo findings from the first large-scale observational study in PSP with 18F-PI-2620 indicated significant elevation of tracer binding in PSP target regions with strongest differences in PSP vs control groups in the globus pallidus internus (mean [SD] distribution volume ratios: PSP-RS, 1.21 [0.10]; PSP-non-RS, 1.12 [0.11]; healthy controls, 1.00 [0.08]; Parkinson disease/multiple system atrophy, 1.03 [0.05]; Alzheimer disease, 1.08 [0.06]). Sensitivity and specificity for detection of PSP-RS vs any control group were 85% and 77%, respectively, when using classification by at least 1 positive target region.

Conclusions and Relevance

This multicenter evaluation indicates a value of 18F-PI-2620 to differentiate suspected patients with PSP, potentially facilitating more reliable diagnosis of PSP.

Early prediction of nonprogression in advanced non-small-cell lung cancer treated with erlotinib by using [(18)F]fluorodeoxyglucose and [(18)F]fluorothymidine positron emission tomography

PURPOSE

Positron emission tomography (PET) with both 2'-deoxy-2'-[(18)F]fluoro-D-glucose (FDG) and 3'-[(18)F]fluoro-3'-deoxy-L-thymidine (FLT) was evaluated with respect to the accuracy of early prediction of nonprogression following erlotinib therapy, independent from epidermal growth factor receptor (EGFR) mutational status, in patients with previously untreated advanced non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Thirty-four patients with untreated stage IV NSCLC were evaluated in this phase II trial. Changes in FDG and FLT uptake after 1 (early) and 6 (late) weeks of erlotinib treatment were compared with nonprogression measured by computed tomography after 6 weeks of treatment, progression-free survival (PFS), and overall survival (OS).

RESULTS

Changes in FDG uptake after 1 week of therapy predicted nonprogression after 6 weeks of therapy with an area under the receiver operating characteristic curve of 0.75 (P = .02). Furthermore, patients with an early metabolic FDG response (cutoff value: 30% reduction in the peak standardized uptake value) had significantly longer PFS (hazard ratio [HR], 0.23; 95% CI, 0.09 to 0.59; P = .002) and OS (HR, 0.36; 95% CI, 0.13 to 0.96; P = .04). Early FLT response also predicted significantly longer PFS (HR, 0.31; 95% CI, 0.10 to 0.95; P = .04) but not OS and was not predictive for nonprogression after 6 weeks of therapy.

CONCLUSION

Early FDG-PET predicts PFS, OS, and nonprogression after 6 weeks of therapy with erlotinib in unselected, previously untreated patients with advanced NSCLC independent from EGFR mutational status.

PSA-Stratified Performance of 18F- and 68Ga-PSMA PET in Patients with Biochemical Recurrence of Prostate Cancer

Several studies outlined the sensitivity of ⁶⁸Ga-labeled PET tracers against the prostate-specific membrane antigen (PSMA) for localization of relapsed prostate cancer in patients with renewed increase in the prostate-specific antigen (PSA), commonly referred to as biochemical recurrence. Labeling of PSMA tracers with ¹⁸F offers numerous advantages, including improved image resolution, longer half-life, and increased production yields. The aim of this study was to assess the PSA-stratified performance of the ¹⁸F-labeled PSMA tracer ¹⁸F-DCFPyL and the ⁶⁸Ga-labeled reference ⁶⁸Ga-PSMA-HBED-CC. Methods: We examined 191 consecutive patients with biochemical recurrence according to standard acquisition protocols using ¹⁸F-DCFPyL (n = 62, 269.8 MBq, PET scan at 120 min after injection) or ⁶⁸Ga-PSMA-HBED-CC (n = 129, 158.9 MBq, 60 min after injection). We determined PSA-stratified sensitivity rates for both tracers and corrected our calculations for Gleason scores using iterative matched-pair analyses. As an orthogonal validation, we directly compared tracer distribution patterns in a separate cohort of 25 patients, sequentially examined with both tracers. Results: After prostatectomy (n = 106), the sensitivity of both tracers was significantly associated with absolute PSA levels (P = 4.3 × 10^-3). Sensitivity increased abruptly, when PSA values exceeded 0.5 μg/L (P = 2.4 × 10^-5). For a PSA less than 3.5 μg/L, most relapses were diagnosed at a still limited stage (P = 3.4 × 10^-6). For a PSA of 0.5-3.5 μg/L, PSA-stratified sensitivity was 88% (15/17) for ¹⁸F-DCFPyL and 66% (23/35) for ⁶⁸Ga-PSMA-HBED-CC. This significant difference was preserved in the Gleason-matched-pair analysis. Outside of this range, sensitivity was comparably low (PSA < 0.5 μg/L) or high (PSA > 3.5 μg/L). After radiotherapy (n = 85), tracer sensitivity was largely PSA-independent. In the 25 patients examined with both tracers, distribution patterns of ¹⁸F-DCFPyL and ⁶⁸Ga-PSMA-HBED-CC were strongly comparable (P = 2.71 × 10^-8). However, in 36% of the PSMA-positive patients we detected additional lesions on the ¹⁸F-DCFPyL scan (P = 3.7 × 10^-2). Conclusion: Our data suggest that ¹⁸F-DCFPyL is noninferior to ⁶⁸Ga-PSMA-HBED-CC, while offering the advantages of ¹⁸F labeling. Our results indicate that imaging with ¹⁸F-DCFPyL may even exhibit improved sensitivity in localizing relapsed tumors after prostatectomy for moderately increased PSA levels. Although the standard acquisition protocols, used for ¹⁸F-DCFPyL and ⁶⁸Ga-PSMA-HBED-CC in this study, stipulate different activity doses and tracer uptake times after injection, our findings provide a promising rationale for validation of ¹⁸F-DCFPyL in future prospective trials.

Molecular Imaging of Proliferation in Malignant Lymphoma

We have determined the ability of positron emission tomography (PET) with the thymidine analogue 3'-deoxy-3'-[(18)F]fluorothymidine (FLT) to detect manifestation sites of malignant lymphoma, to assess proliferative activity, and to differentiate aggressive from indolent tumors. In this prospective study, FLT-PET was done additionally to routine staging procedures in 34 patients with malignant lymphoma. Sixty minutes after i.v. injection of approximately 330 MBq FLT, emission and transmission scanning was done. Tracer uptake in lymphoma was evaluated semiquantitatively by calculation of standardized uptake values (SUV) and correlated to tumor grading and proliferation fraction as determined by Ki-67 immunohistochemistry. FLT-PET detected a total of 490 lesions compared with 420 lesions revealed by routine staging. In 11 patients with indolent lymphoma, mean FLT-SUV in biopsied lesions was 2.3 (range, 1.2-4.5). In 21 patients with aggressive lymphoma, a significantly higher FLT uptake was observed (mean FLT-SUV, 5.9; range, 3.2-9.2; P < 0.0001) and a cutoff value of SUV = 3 accurately discriminated between indolent and aggressive lymphoma. Linear regression analysis indicated significant correlation of FLT uptake in biopsied lesions and proliferation fraction (r = 0.84; P < 0.0001). In this clinical study, FLT-PET was suitable for imaging malignant lymphoma and noninvasive assessment of tumor grading. Due to specific imaging of proliferation, FLT may be a superior PET tracer for detection of malignant lymphoma in organs with high physiologic fluorodeoxyglucose uptake and early detection of progression to a more aggressive histology or potential transformation.

Carbon-11 acetate positron emission tomography can detect local recurrence of prostate cancer

We investigated the potential of [(11)C]acetate positron emission tomography (PET) to detect local recurrence in prostate cancer (PCA) in patients with increasing PSA following complete prostatectomy. A total of 31 patients were studied and compared with the results of transrectal ultrasound (TRUS) combined with biopsy and clinical follow-up. Whole-body PET scan was performed 5 min after injection of 0.8 GBq [(11)C]acetate and completed within 1 h. Focally increased tracer uptake below the urinary bladder or in an abdominal lymph node region was considered as relapse. TRUS followed by biopsy verified recurrence in 18 patients and ruled it out in 13 patients. PET demonstrated local recurrence in 15 out of the aforementioned 18 patients. PET also demonstrated distant lymph node involvement and bone metastases in five patients each. No focal [(11)C]acetate uptake was demonstrated in the prostate bed in patients with negative biopsy. These patients had no evidence of disease during 6 months of follow-up. In the subgroup of patients with PSA <2.0 ng/ml ( n=8), five patients had positive PET findings, with four of them verified by biopsy. It is concluded that [(11)C]acetate PET is a promising new tool for the diagnosis of PCA recurrence and can influence patient management.

Copper-mediated aromatic radiofluorination revisited: efficient production of PET tracers on a preparative scale

Two novel methods for copper-mediated aromatic nucleophilic radiofluorination were recently reported. Evaluation of these methods reveals that, although both are efficient in small-scale experiments, they are inoperative for the production of positron emission tomography (PET) tracers. Since high base content turned out to be responsible for low radiochemical conversions, a "low base" protocol has been developed which affords (18)F-labeled arenes from diaryliodonium salts and aryl pinacol boronates in reasonable yields. Furthermore, implementation of our "minimalist" approach to the copper-mediated [(18)F]-fluorination of (mesityl)(aryl)iodonium salts allows the preparation of (18)F-labeled arenes in excellent RCCs. The novel radiofluorination method circumvents time-consuming azeotropic drying and avoids the utilization of base and other additives, such as cryptands. Furthermore, this procedure enables the production of clinically relevant PET tracers; [(18)F]FDA, 4-[(18)F]FPhe, and [(18)F]DAA1106 are obtained in good isolated radiochemical yields. Additionally, [(18)F]DAA1106 has been evaluated in a rat stroke model and demonstrates excellent potential for visualization of translocator protein 18 kDa overexpression associated with neuroinflammation after ischemic stroke.

Combined FET PET/MRI radiomics differentiates radiation injury from recurrent brain metastasis

Background

The aim of this study was to investigate the potential of combined textural feature analysis of contrast-enhanced MRI (CE-MRI) and static O-(2-[¹⁸F]fluoroethyl)-L-tyrosine (FET) PET for the differentiation between local recurrent brain metastasis and radiation injury since CE-MRI often remains inconclusive.

Methods

Fifty-two patients with new or progressive contrast-enhancing brain lesions on MRI after radiotherapy (predominantly stereotactic radiosurgery) of brain metastases were additionally investigated using FET PET. Based on histology (n = 19) or clinicoradiological follow-up (n = 33), local recurrent brain metastases were diagnosed in 21 patients (40%) and radiation injury in 31 patients (60%). Forty-two textural features were calculated on both unfiltered and filtered CE-MRI and summed FET PET images (20–40 min p.i.), using the software LIFEx. After feature selection, logistic regression models using a maximum of five features to avoid overfitting were calculated for each imaging modality separately and for the combined FET PET/MRI features. The resulting models were validated using cross-validation. Diagnostic accuracies were calculated for each imaging modality separately as well as for the combined model.

Results

For the differentiation between radiation injury and recurrence of brain metastasis, textural features extracted from CE-MRI had a diagnostic accuracy of 81% (sensitivity, 67%; specificity, 90%). FET PET textural features revealed a slightly higher diagnostic accuracy of 83% (sensitivity, 88%; specificity, 75%). However, the highest diagnostic accuracy was obtained when combining CE-MRI and FET PET features (accuracy, 89%; sensitivity, 85%; specificity, 96%).

Conclusions

Our findings suggest that combined FET PET/CE-MRI radiomics using textural feature analysis offers a great potential to contribute significantly to the management of patients with brain metastases.

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Differentiation between brain metastasis recurrence and radiation injury is of high clinical importance.

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Differentiation based on contrast-enhanced conventional MRI is often inconclusive.

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Radiomics and hybrid amino acid PET/MR imaging are increasingly gaining attention in Neuro-Oncology.

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We investigated the potential of combined PET/MRI radiomics analysis using MRI and FET PET in patients with brain metastases.

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Combined PET/MRI radiomics allows the differentiation of brain metastasis recurrence from radiation injury with high accuracy.

In vivo imaging of activated microglia using [11C]PK11195 and positron emission tomography in patients after ischemic stroke

Neuroprotective strategies are currently being developed for stroke patients. Although the focus is on the development of early treatment the importance of late pathogenetic events is increasingly recognized. To investigate the microglial reaction in stroke we used a marker for activated microglia, [11C]PK11195, and PET in five patients with ischemic stroke 5-53 days after infarction. In one patient serial measurements were made. We demonstrated in each individual and at each point in time that a microglial reaction takes place in the area where T1 weighted MRI (magnetic resonance imaging) shows intensity changes. We consider this PET method as a promising tool to study the late pathogenetic consequences of cerebral infarction and to evaluate neuroprotective strategies with respect to the consequences of the microglial activation.

In vivo Patterns of Tau Pathology, Amyloid-β Burden, and Neuronal Dysfunction in Clinical Variants of Alzheimer's Disease

The clinical heterogeneity of Alzheimer's disease is not reflected in the rather diffuse cortical deposition of amyloid-β. We assessed the relationship between clinical symptoms, in vivo tau pathology, amyloid distribution, and hypometabolism in variants of Alzheimer's disease using novel multimodal PET imaging techniques. Tau pathology was primarily observed in brain regions related to clinical symptoms and overlapped with areas of hypometabolism. In contrast, amyloid-β deposition was diffusely distributed over the entire cortex. Tau PET imaging may thus serve as a valuable biomarker for the localization of neuronal injury in vivo and may help to validate atypical subtypes of Alzheimer's disease.

Cholinergic system function and cognition in mild cognitive impairment

Evidence for cholinergic dysfunction in very early stages of neurodegeneration like mild cognitive impairment (MCI) is inconclusive. Previous positron emission tomography (PET) studies based on small samples investigated if it is related to memory impairment. We examined whether cortical acetylcholine esterase (AChE) activity is reduced at this stage and correlated with cognitive function. N-[(11)C]-methyl-4-piperidyl acetate ([11C]MP4A), a positron emission tomography tracer for measuring cerebral AChE activity in vivo, was applied in 21 controls and 17 MCI patients. Parametric images of AChE activity were analyzed using standard atlas regions. Principal components analysis (PCA) of regional values of AChE activity and correlation analysis with neuropsychological test results was performed. Cortical AChE activity showed a significant decline in MCI patients compared with controls which was most pronounced in temporal regions. They formed the main part of a principal component that was related significantly to verbal and nonverbal memory, language comprehension and executive function. Cholinergic dysfunction is an early hallmark even before onset of dementia at the clinical stage of MCI. Its impact especially on temporal neocortex is associated with impaired neuropsychological function.

Impact of tau and amyloid burden on glucose metabolism in Alzheimer's disease

In a multimodal PET imaging approach, we determined the differential contribution of neurofibrillary tangles (measured with [¹⁸F]AV‐1451) and beta‐amyloid burden (measured with [¹¹C]PiB) on degree of neurodegeneration (i.e., glucose metabolism measured with [¹⁸F]FDG‐PET) in patients with Alzheimer's disease. Across brain regions, we observed an interactive effect of beta‐amyloid burden and tau deposition on glucose metabolism which was most pronounced in the parietal lobe. Elevated beta‐amyloid burden was associated with a stronger influence of tau accumulation on glucose metabolism. Our data provide the first in vivo insights into the differential contribution of Aβ and tau to neurodegeneration in Alzheimer's disease.

Predicting IDH genotype in gliomas using FET PET radiomics

Mutations in the isocitrate dehydrogenase (IDH mut) gene have gained paramount importance for the prognosis of glioma patients. To date, reliable techniques for a preoperative evaluation of IDH genotype remain scarce. Therefore, we investigated the potential of O-(2-[18F]fluoroethyl)-L-tyrosine (FET) PET radiomics using textural features combined with static and dynamic parameters of FET uptake for noninvasive prediction of IDH genotype. Prior to surgery, 84 patients with newly diagnosed and untreated gliomas underwent FET PET using a standard scanner (15 of 56 patients with IDH mut) or a dedicated high-resolution hybrid PET/MR scanner (11 of 28 patients with IDH mut). Static, dynamic and textural parameters of FET uptake in the tumor area were evaluated. Diagnostic accuracy of the parameters was evaluated using the neuropathological result as reference. Additionally, FET PET and textural parameters were combined to further increase the diagnostic accuracy. The resulting models were validated using cross-validation. Independent of scanner type, the combination of standard PET parameters with textural features increased significantly diagnostic accuracy. The highest diagnostic accuracy of 93% for prediction of IDH genotype was achieved with the hybrid PET/MR scanner. Our findings suggest that the combination of conventional FET PET parameters with textural features provides important diagnostic information for the non-invasive prediction of the IDH genotype.

FET PET reveals considerable spatial differences in tumour burden compared to conventional MRI in newly diagnosed glioblastoma

PURPOSE

Areas of contrast enhancement (CE) on MRI are usually the target for resection or radiotherapy target volume definition in glioblastomas. However, the solid tumour mass may extend beyond areas of CE. Amino acid PET can detect parts of the tumour that show no CE. We systematically investigated tumour volumes delineated by amino acid PET and MRI in patients with newly diagnosed, untreated glioblastoma.

METHODS

Preoperatively, 50 patients with neuropathologically confirmed glioblastoma underwent O-(2-[¹⁸F]-fluoroethyl)-L-tyrosine (FET) PET, and fluid-attenuated inversion recovery (FLAIR) and contrast-enhanced MRI. Areas of CE were manually segmented. FET PET tumour volumes were segmented using a tumour-to-brain ratio of ≥1.6. The percentage overlap volumes, and Dice and Jaccard spatial similarity coefficients (DSC, JSC) were calculated. FLAIR images were evaluated visually.

RESULTS

In 43 patients (86%), the FET tumour volume was significantly larger than the CE volume (21.5 ± 14.3 mL vs. 9.4 ± 11.3 mL; P < 0.001). Forty patients (80%) showed both increased uptake of FET and CE. In these 40 patients, the spatial similarity between FET uptake and CE was low (mean DSC 0.39 ± 0.21, mean JSC 0.26 ± 0.16). Ten patients (20%) showed no CE, and one of these patients showed no FET uptake. In five patients (10%), increased FET uptake was present outside areas of FLAIR hyperintensity.

CONCLUSION

Our results show that the metabolically active tumour volume delineated by FET PET is significantly larger than tumour volume delineated by CE. Furthermore, the results strongly suggest that the information derived from both imaging modalities should be integrated into the management of patients with newly diagnosed glioblastoma.

188Re or 90Y-labelled anti-CD66 antibody as part of a dose-reduced conditioning regimen for patients with acute leukaemia or myelodysplastic syndrome over the age of 55: results of a phase I-II study

In a phase I-II study for patients aged 55-65 years, we employed radioimmunotherapy using an anti-CD-66 antibody as part of a dose-reduced conditioning regimen, which was followed by a T-cell-depleted graft. 20 patients with a median age of 63 years suffering from acute leukaemia (n=17) or myelodysplastic syndrome (n=3) received the antibody labelled either with 188Rhenium (n=8) or with 90Yttrium (n=12) during conditioning. Radioimmunotherapy provided a mean dose of 21.9 (+/-8.4) Gy to the bone marrow with a significantly higher dose when 90Yttrium was used. Additional conditioning was fludarabine-based plus anti-thymocyte globulin in matched related donor transplants (n=11), or plus melphalan in matched unrelated donor transplants (n=9). Regimen-related toxicity was low, with two patients developing three episodes of grade III organ toxicity. All patients engrafted, grade II-IV acute graft-versus-host disease (GvHD) was observed in one patient (5%) and chronic GvHD in three patients (15%). The cumulative incidence of non-relapse mortality was 25%, the cumulative incidence of relapse 55%. The probability of survival was estimated to be 70% at 1 year and 52% at 2 years post-transplant, although no plateau was reached afterwards. In conclusion, radioimmunotherapy using the anti-CD66 antibody was feasible and safe in our elderly patient group and provided a high marrow dose.

Clinical relevance of imaging proliferative activity in lung nodules

PURPOSE

Recently, 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.

METHODS

A 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 43 patients 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.

RESULTS

Histopathology 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 two patients with non-small cell lung cancer, in the patient with a pulmonary carcinoid and in three patients 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 7/15 patients, 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.

CONCLUSION

FLT-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.

Neither azeotropic drying, nor base nor other additives: a minimalist approach to 18F-labeling

A novel radiofluorination procedure using only precursor and [¹⁸F]fluoride without the need for azeotropic drying, base and other ingredients was developed.

Early detection of erlotinib treatment response in NSCLC by 3'-deoxy-3'-[F]-fluoro-L-thymidine ([F]FLT) positron emission tomography (PET)

Background

Inhibition of the epidermal growth factor receptor (EGFR) has shown clinical success in patients with advanced non-small cell lung cancer (NSCLC). Somatic mutations of EGFR were found in lung adenocarcinoma that lead to exquisite dependency on EGFR signaling; thus patients with EGFR-mutant tumors are at high chance of response to EGFR inhibitors. However, imaging approaches affording early identification of tumor response in EGFR-dependent carcinomas have so far been lacking.

Methodology/Principal Findings

We performed a systematic comparison of 3′-Deoxy-3′-[¹⁸F]-fluoro-L-thymidine ([¹⁸F]FLT) and 2-[¹⁸F]-fluoro-2-deoxy-D-glucose ([¹⁸F]FDG) positron emission tomography (PET) for their potential to identify response to EGFR inhibitors in a model of EGFR-dependent lung cancer early after treatment initiation. While erlotinib-sensitive tumors exhibited a striking and reproducible decrease in [¹⁸F]FLT uptake after only two days of treatment, [¹⁸F]FDG PET based imaging revealed no consistent reduction in tumor glucose uptake. In sensitive tumors, a decrease in [¹⁸F]FLT PET but not [¹⁸F]FDG PET uptake correlated with cell cycle arrest and induction of apoptosis. The reduction in [¹⁸F]FLT PET signal at day 2 translated into dramatic tumor shrinkage four days later. Furthermore, the specificity of our results is confirmed by the complete lack of [¹⁸F]FLT PET response of tumors expressing the T790M erlotinib resistance mutation of EGFR.

Conclusions

[¹⁸F]FLT PET enables robust identification of erlotinib response in EGFR-dependent tumors at a very early stage. [¹⁸F]FLT PET imaging may represent an appropriate method for early prediction of response to EGFR TKI treatment in patients with NSCLC.

Transcranial direct current stimulation accelerates recovery of function, induces neurogenesis and recruits oligodendrocyte precursors in a rat model of stroke

BACKGROUND

Clinical data suggest that transcranial direct current stimulation (tDCS) may be used to facilitate rehabilitation after stroke. However, data are inconsistent and the neurobiological mechanisms underlying tDCS remain poorly explored, impeding its implementation into clinical routine. In the healthy rat brain, tDCS affects neural stem cells (NSC) and microglia. We here investigated whether tDCS applied after stroke also beneficially affects these cells, which are known to be involved in regeneration and repair.

METHODS

Focal cerebral ischemia was induced in rats by transient occlusion of the middle cerebral artery. Twenty-eight animals with comparable infarcts, as judged by magnetic resonance imaging, were randomized to receive a multi-session paradigm of either cathodal, anodal, or sham tDCS. Behaviorally, recovery of motor function was assessed by Catwalk. Proliferation in the NSC niches was monitored by Positron-Emission-Tomography (PET) employing the radiotracer 3'-deoxy-3'-[(18)F]fluoro-l-thymidine ([(18)F]FLT). Microglia activation was depicted with [(11)C]PK11195-PET. In addition, immunohistochemical analyses were used to quantify neuroblasts, oligodendrocyte precursors, and activation and polarization of microglia.

RESULTS

Anodal and cathodal tDCS both accelerated functional recovery, though affecting different aspects of motor function. Likewise, tDCS induced neurogenesis independently of polarity, while only cathodal tDCS recruited oligodendrocyte precursors towards the lesion. Moreover, cathodal stimulation preferably supported M1-polarization of microglia.

CONCLUSIONS

TDCS acts through multifaceted mechanisms that far exceed its primary neurophysiological effects, encompassing proliferation and migration of stem cells, their neuronal differentiation, and modulation of microglia responses.