Does FDG PET-Based Radiomics Have an Added Value for Prediction of Overall Survival in Non-Small Cell Lung Cancer?

Objectives: Radiomics and machine learning are innovative approaches to improve the clinical management of NSCLC. However, there is less information about the additive value of FDG PET-based radiomics compared with clinical and imaging variables. Methods: This retrospective study included 320 NSCLC patients who underwent PET/CT with FDG at initial staging. VOIs were placed on primary tumors only. We included a total of 94 variables, including 87 textural features extracted from PET studies, SUVmax, MTV, TLG, TNM stage, histology, age, and gender. We used the least absolute shrinkage and selection operator (LASSO) regression to select variables with the highest predictive value. Although several radiomics variables are available, the added value of these predictors compared with clinical and imaging variables is still under evaluation. Three hundred and twenty NSCLC patients were included in this retrospective study and underwent 18F-FDG PET/CT at initial staging. In this study, we evaluated 94 variables, including 87 textural features, SUVmax, MTV, TLG, TNM stage, histology, age, and gender. Image-based predictors were extracted from a volume of interest (VOI) positioned on the primary tumor. The least absolute shrinkage and selection operator (LASSO) Cox regression was used to reduce the number of variables and select only those with the highest predictive value. The predictive model implemented with the variables selected using the LASSO analysis was compared with a reference model using only a tumor stage and SUVmax. Results: NGTDM coarseness, SUVmax, and TNM stage survived the LASSO analysis and were used for the radiomic model. The AUCs obtained from the reference and radiomic models were 80.82 (95%CI, 69.01-92.63) and 81.02 (95%CI, 69.07-92.97), respectively (p = 0.98). The median OS in the reference model was 17.0 months in high-risk patients (95%CI, 11-21) and 113 months in low-risk patients (HR 7.47, p < 0.001). In the radiomic model, the median OS was 16.5 months (95%CI, 11-20) and 113 months in high- and low-risk groups, respectively (HR 9.64, p < 0.001). Conclusions: Our results indicate that a radiomic model composed using the tumor stage, SUVmax, and a selected radiomic feature (NGTDM_Coarseness) predicts survival in NSCLC patients similarly to a reference model composed only by the tumor stage and SUVmax. Replication of these preliminary results is necessary.

Multivariable Risk Modelling and Survival Analysis with Machine Learning in SARS-CoV-2 Infection

AIM

To evaluate the performance of a machine learning model based on demographic variables, blood tests, pre-existing comorbidities, and computed tomography(CT)-based radiomic features to predict critical outcome in patients with acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

METHODS

We retrospectively enrolled 694 SARS-CoV-2-positive patients. Clinical and demographic data were extracted from clinical records. Radiomic data were extracted from CT. Patients were randomized to the training (80%, n = 556) or test (20%, n = 138) dataset. The training set was used to define the association between severity of disease and comorbidities, laboratory tests, demographic, and CT-based radiomic variables, and to implement a risk-prediction model. The model was evaluated using the C statistic and Brier scores. The test set was used to assess model prediction performance.

RESULTS

Patients who died (n = 157) were predominantly male (66%) over the age of 50 with median (range) C-reactive protein (CRP) = 5 [1, 37] mg/dL, lactate dehydrogenase (LDH) = 494 [141, 3631] U/I, and D-dimer = 6.006 [168, 152.015] ng/mL. Surviving patients (n = 537) had median (range) CRP = 3 [0, 27] mg/dL, LDH = 484 [78, 3.745] U/I, and D-dimer = 1.133 [96, 55.660] ng/mL. The strongest risk factors were D-dimer, age, and cardiovascular disease. The model implemented using the variables identified using the LASSO Cox regression analysis classified 90% of non-survivors as high-risk individuals in the testing dataset. In this sample, the estimated median survival in the high-risk group was 9 days (95% CI; 9-37), while the low-risk group did not reach the median survival of 50% (p < 0.001).

CONCLUSIONS

A machine learning model based on combined data available on the first days of hospitalization (demographics, CT-radiomics, comorbidities, and blood biomarkers), can identify SARS-CoV-2 patients at risk of serious illness and death.

Assessment of Response to Immunotherapy in Patients with Hodgkin Lymphoma: Towards Quantifying Changes in Tumor Burden Using FDG-PET/CT

Immune checkpoint inhibitors are currently the standard of care for many advanced solid tumors, and they have been recently approved for the treatment of relapsed/refractory Hodgkin lymphoma and primary mediastinal B cell lymphoma. Assessments of the response to immunotherapy may be complicated by the occurrence of the flare/pseudoprogression phenomenon, consisting of initial tumor enlargement and even the appearance of new lesions, followed by a response, which may initially be indistinguishable from true progression. There have been efforts to characterize and capture the new patterns of response observed during immunotherapy, namely, pseudoprogression and delayed response, and several immune-related response criteria have been proposed. Confirming progression on a subsequent scan and measuring the total tumor burden are both common in immune-related criteria. Due to the peculiarity of hematologic malignancies, lymphoma-specific immune-related criteria have been developed (LYRIC), and they have been evaluated in research studies in comparison to the Lugano Classification. In this review work, we illustrate the evolution of the response criteria in lymphomas from the first CT-based criteria to the development of the PET-based Lugano Classification, further refined to take into account the flare phenomenon encountered during immunotherapy. We also describe the additional contribution of PET-derived volumetric parameters to the interpretation of responses during immunotherapy.

Machine Learning Model to Predict Diagnosis of Mild Cognitive Impairment by Using Radiomic and Amyloid Brain PET

PURPOSE

The study aimed to develop a deep learning model for predicting amnestic mild cognitive impairment (aMCI) diagnosis using radiomic features and amyloid brain PET.

PATIENTS AND METHODS

Subjects (n = 328) from the Alzheimer's Disease Neuroimaging Initiative database and the EudraCT 2015-001184-39 trial (159 males, 169 females), with a mean age of 72 ± 7.4 years, underwent PET/CT with 18 F-florbetaben. The study cohort consisted of normal controls (n = 149) and subjects with aMCI (n = 179). Thirteen gray-level run-length matrix radiomic features and amyloid loads were extracted from 27 cortical brain areas. The least absolute shrinkage and selection operator regression was used to select features with the highest predictive value. A feed-forward neural multilayer network was trained, validated, and tested on 70%, 15%, and 15% of the sample, respectively. Accuracy, precision, F1-score, and area under the curve were used to assess model performance. SUV performance in predicting the diagnosis of aMCI was also assessed and compared with that obtained from the machine learning model.

RESULTS

The machine learning model achieved an area under the receiver operating characteristic curve of 90% (95% confidence interval, 89.4-90.4) on the test set, with 80% and 78% for accuracy and F1-score, respectively. The deep learning model outperformed SUV performance (area under the curve, 71%; 95% confidence interval, 69.7-71.4; 57% accuracy, 48% F1-score).

CONCLUSIONS

Using radiomic and amyloid PET load, the machine learning model identified MCI subjects with 84% specificity at 81% sensitivity. These findings show that a deep learning algorithm based on radiomic data and amyloid load obtained from brain PET images improves the prediction of MCI diagnosis compared with SUV alone.

Methodological aspects and prognostic value of metabolic tumor volume assessed with 18F-FDG PET/CT in lymphomas

Metabolic tumor volume (MTV) assessed by pretreatment 18F-FDG PET/CT has shown significant prognostic value across many lymphoma types, although not yet used in clinical practice for technical concerns and need for standardization. Numerous studies on the prognostic value of MTV in lymphomas have been published in recent years, but there is still no full agreement on the best methodology for MTV calculation. In this paper, we reviewed the methodological aspects of MTV assessment and reported recent works about its impact on outcome in lymphomas, with a focus on Hodgkin lymphoma (HL) and diffuse large B cell lymphoma (DLBCL).

Toward the Discovery and Development of PSMA Targeted Inhibitors for Nuclear Medicine Applications

BACKGROUND

The rising incidence rate of prostate cancer (PCa) has promoted the development of new diagnostic and therapeutic radiopharmaceuticals during the last decades. Promising improvements have been achieved in clinical practice using prostate specific membrane antigen (PSMA) labeled agents, including specific antibodies and small molecular weight inhibitors. Focusing on molecular docking studies, this review aims to highlight the progress in the design of PSMA targeted agents for a potential use in nuclear medicine.

RESULTS

Although the first development of radiopharmaceuticals able to specifically recognize PSMA was exclusively oriented to macromolecule protein structure such as radiolabeled monoclonal antibodies and derivatives, the isolation of the crystal structure of PSMA served as the trigger for the synthesis and the further evaluation of a variety of low molecular weight inhibitors. Among the nuclear imaging probes and radiotherapeutics that have been developed and tested till today, labeled Glutamate-ureido inhibitors are the most prevalent PSMA-targeting agents for nuclear medicine applications.

CONCLUSION

PSMA represents for researchers the most attractive target for the detection and treatment of patients affected by PCa using nuclear medicine modalities. [99mTc]MIP-1404 is considered the tracer of choice for SPECT imaging and [68Ga]PSMA-11 is the leading diagnostic for PET imaging by general consensus. [18F]DCFPyL and [18F]PSMA-1007 are clearly the emerging PET PSMA candidates for their great potential for a widespread commercial distribution. After paving the way with new imaging tools, academic and industrial R&Ds are now focusing on the development of PSMA inhibitors labeled with alpha or beta minus emitters for a theragnostic application.

Impact of Tracer Retention Levels on Visual Analysis of Cerebral [18F]- Florbetaben Pet Images

BACKGROUND

To compare visual and semi-quantitative analysis of brain [¹⁸F]Florbetaben PET images in Mild Cognitive Impairment (MCI) patients and relate this finding to the degree of ß-amyloid burden.

METHODS

A sample of 71 amnestic MCI patients (age 74 ± 7.3 years, Mini Mental State Examination 24.2 ± 5.3) underwent cerebral [¹⁸F]Florbetaben PET/CT. Images were visually scored as positive or negative independently by three certified readers blinded to clinical and neuropsychological assessment. Amyloid positivity was also assessed by semiquantitative approach by means of a previously published threshold (SUVr ≥ 1.3). Fleiss kappa coefficient was used to compare visual analysis (after consensus among readers) and semi-quantitative analysis. Statistical significance was taken at P<0.05.

RESULTS

After the consensus reading, 43/71 (60.6%) patients were considered positive. Cases that were interpreted as visually positive had higher SUVr than visually negative patients (1.48 ± 0.19 vs 1.11 ± 0.09) (P<0.05). Agreement between visual analysis and semi-quantitative analysis was excellent (k=0.86, P<0.05). Disagreement occurred in 7/71 patients (9.9%) (6 false positives and 1 false negative). Agreement between the two analyses was 90.0% (18/20) for SUVr < 1.1, 83% (24/29) for SUVr between 1.1 and 1.5, and 100% (22/22) for SUVr > 1.5 indicating lowest agreement for the group with intermediate amyloid burden.

CONCLUSION

Inter-rater agreement of visual analysis of amyloid PET images is high. Agreement between visual analysis and SUVr semi-quantitative analysis decreases in the range of 1.1<SUVr <=1.5, where the clinical scenario is more challenging.

The brain cognitive reserve hypothesis: A review with emphasis on the contribution of nuclear medicine neuroimaging techniques

Neuropathological and clinical evidence indicates that the clinical expression of Alzheimer's disease (AD) occurs as neuropathology exceeds the brain reserve capacity. The brain or cognitive reserve (BCR) hypothesis states that high premorbid intelligence, education, and an active and stimulating lifestyle provide reserve capacity, which acts as a buffer against the cognitive deficits due to accumulating neuropathology. Neuroimaging studies that assessed the BCR hypothesis are critically reviewed with emphasis on study design and statistical analysis. Many studies were performed in the last two decades owing to the increasing availability of positron emission tomography (PET) and PET/computed tomography scanners and to the synthesis of new radiopharmaceuticals, including tracers for amyloid and tau proteins. Studies with different tracers provided complementary consistent results supporting the BCR hypothesis. Many studies were appropriately designed with a measure of reserve, a measure of brain anatomy/function/neuropathology, and a measure of cognitive functions that are necessary. Most of the early studies were performed with PET and [ ¹⁸ F]fluorodeoxyglucose, and occasionally with [ ¹⁵ O]water, reporting a significant association between higher occupation/education and lower glucose metabolism (blood flow) in associative temporo-parietal cortex in patients with AD and also in patients with MCI, after correcting for the degree in the cognitive impairment. On the contrary, performances on several neuropsychological tests increased with increasing education for participants with elevated [ ¹¹ C]PiB uptake. Studies with the tracers specific for tau protein showed that patients with AD with elevated tau deposits had higher cognitive performances compared with patients with similar levels of tau deposits. BCR in AD is also associated with a preserved cholinergic function. The BCR hypothesis has been validated with methodologically sound study designs and sophisticated neuroimaging techniques using different radiotracers and providing an explanation for neuropathological and clinical observations on patients with AD.

[68Ga]-Dota Peptide PET/CT in Neuroendocrine Tumors: Main Clinical Applications

Objective:

Neuroendocrine Neoplasms (NENs) are generally defined as rare and heterogeneous tumors. The gastrointestinal system is the most frequent site of NENs localization, however they can be found in other anatomical regions, such as pancreas, lungs, ovaries, thyroid, pituitary, and adrenal glands. Neuroendocrine neoplasms have significant clinical manifestations depending on the production of active peptide.

Methods:

Imaging modalities play a fundamental role in initial diagnosis as well as in staging and treatment monitoring of NENs, in particular they vastly enhance the understanding of the physiopathology and diagnosis of NENs through the use of somatostatin analogue tracers labeled with appropriate radioisotopes. Additionally, the use of somatostatin analogues provides the ability to in-vivo measure the expression of somatostatin receptors on NEN cells, a process that might have important therapeutic implications.

Results:

A large body of evidences showed improved accuracy of molecular imaging based on PET/CT radiotracer with SST analogues (e.g. [68Ga]-DOTA peptide) for the detection of NEN lesions in comparison to morphological imaging modalities. So far, the role of imaging technologies in assessing treatment response is still under debate.

Conclusion:

This review offers the systems of classification and grading of NENs and summarizes the more useful recommendations based on data recently published for the management of patients with NENs, with special focus on the role of imaging modalities based on SST targeting with PET / CT radiotracers.

11C-choline PET/CT predicts survival in prostate cancer patients with PSA < 1 NG/ml

PURPOSE

The main drawback of ¹¹C-choline PET/CT for restaging prostate cancer (PCa) patients with biochemical failure is the relatively low positive detection rate for prostate specific antigen (PSA) < 1 ng/ml. This study assessed whether ¹¹C-choline PET/CT predicts survival in PCa patients with PSA < 1 ng/ml.

METHODS

This retrospective study included 210 PCa patients treated with radical prostatectomy who underwent ¹¹C-choline PET/CT from December 1, 2004 to July 31, 2007 due to biochemical failure. PCa-specific survival was estimated using Kaplan-Meier curves. Cox regression analysis was used to evaluate the association between clinicopathologic variables and PCa-specific survival. PCa-specific survival was computed as the interval from radical prostatectomy to PCa-specific death.

RESULTS

Median follow-up after radical prostatectomy was 6.9 years (95% confidence interval, CI, 2.0-14.5 years). ¹¹C-choline PET/CT was positive in 20.5% of patients. Median PCa-specific survival was 13.4 years (95% CI, 9.9-16.8 years) in patients with positive ¹¹C-choline PET/CT, and it was not achieved in patients with negative ¹¹C-choline PET/CT (log-rank, chi-square = 15.0, P < 0.001). Ten-year survival probabilities for patients with negative ¹¹C-choline PET/CT and for patients with positive ¹¹C-choline PET/CT were 86.0% (95% CI: 80.7%-91.3%) and 63.6% (95% CI: 54.5-72.7%). At multivariate analysis, only ¹¹C-choline PET/CT significantly predicted PCa-specific survival (hazard ratio = 2.54, 95% CI, 1.05-6.13, P = 0.038). Patients with pathological ¹¹C-choline uptake in the prostatic bed or in pelvic lymph nodes had longer PCa-specific survival in comparison to patients with pathological tracer uptake in the skeleton (log-rank: chi-square = 27.4, P < 0.001).

CONCLUSION

Despite the relatively low positive detection rate for PSA < 1 ng/ml, positive ¹¹C-choline PET/CT predicts PCa-specific survival in this low PSA range. As long as more sensitive radiotracers, such as ⁶⁸Ga-PSMA-11, do not become more widely available, these results might support a broader use of radiolabeled choline in restaging PCa for PSA < 1 ng/ml.

PET/CT With 68Ga-PSMA in Prostate Cancer: Radiopharmaceutical Background and Clinical Implications

BACKGROUND AND OBJECTIVE

In the last twenty years, positron emission tomography / computed tomography (PET/CT) with radiolabeled choline, represented the most powerful imaging modality for prostate cancer (PCa). However, the low positive detection rate of the technique for PSA < 1 ng/ml prompted the development of other tracers for imaging PCa.

METHODS

We performed a critical review of 68Ga-PSMA, a receptor ligand tracer, which has been identified as the most promising radiopharmaceutical for imaging PCa.

RESULTS

The most promising feature of this radiopharmaceutical is the high positive detection rate for prostate specific antigen (PSA) levels < 1 ng/ml or less (i.e., PSA < 0.5 ng/ml). 68Ga-PSMA detection rate is also sensitive to PSA kinetics, expressed either as PSA doubling time or PSA velocity. There are initial results indicating that 68Ga-PSMA may significantly affect the clinical management of PCa patients, even though the additional advantages in comparison to radiolabeled choline need to be further supported in future perspective studies. Other clinical implications, such as whether 68Ga-PSMA PET/CT predicts PCa-specific survival, have not yet been investigated. Numerous clinical studies have been published, some of them with histopathological verification so that despite the recent introduction in the clinical field reliable estimation of sensitivity and specificity of 68Ga-PSMA PET/CT have been obtained through meta-analyses. Most clinical studies with PET/CT with 68Ga-PSMA are retrospective, single-institutional studies and in many cases include heterogeneous patient cohorts. Thus, multidisciplinary, well-throughout prospective trials are needed to better define the clinical implications of 68Ga- PSMA PET/CT in PCa patients. The increasing availability of positron emission tomography / magnetic resonance (PET/MR) hybrid devices promotes the use of this radiopharmaceutical especially at initial staging when identification of tumor localization and of extra-prostatic disease represent clinically relevant questions. PSMA cold ligands can also be labeled with beta emitters with good chemical stability so that 68Ga-PSMA PET/CT can be used to guide radiometabolic therapy of advanced metastatic PCa patients through 177Lu-labeled PSMA ligands.

CONCLUSION

PSMA labeled ligands appear very promising for diagnosis and treatment of PCa.

Radiopharmaceuticals for the Diagnosis and Therapy of Neuroendocrine Differentiated Prostate Cancer

Neuroendocrine differentiation of prostate cancer (PCa) is a relatively frequent event, generally understudied, that carries important prognostic information. It is the most frequently observed during the advanced stages of disease, when PCa has lost its sensitivity to androgen deprivation therapy or to chemotherapy, moderate to diffuse bone metastatic spread dominates the imaging scenario and it is responsible for painful clinical symptomatology. However, evidences indicate that neuroendocrine differentiation is a progressive phenomenon that starts at the very early part of the pathogenesis of cancer transformation contributing to it. Neuroendocrine tumor phenotypes have reduced capability to secrete the prostate specific antigen (PSA) and therefore PSA does not represent a reliable marker to follow-up neuroendocrine differentiation. Tumor progression may be monitored by measuring plasma concentration of neuroendocrine tumor markers, primarily chromogranin A and neuron-specific enolase. Several nuclear medicine tracers are available for studying different biochemical properties of tumor cells with neuroendocrine differentiation. Single photon computed emission tomography (SPECT) with [111In-diethylenetriaminepentaacetic acid] ([111In-DTPA0])- octreotide (Octreoscan) has been extensively used in the past. However, the development of the chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), which in comparison to DTPA allows higher affinity bindings for beta-emitting radionuclides and for somatostatin (SST) analogues, and the increased availability of the Germanium-68/Gallium-68 (68Ge/68Ga)-generator, which enables positron emission tomography/computed tomography (PET/CT) imaging, have allowed the synthesis of several PET tracers for different SST receptors. The receptor of the bombesin/ gastrin releasing peptide (GRP), which is overexpressed in PCa with neuroendocrine differentiation, also represents an innovative research field with diagnostic and therapeutic applications through, respectively, positron and beta emitters. At the moment, however, we observe some discrepancy between the high number of preclinical studies and the small number of clinical studies, most likely related to competing and, at the moment, more effective radiopharmaceuticals for imaging and for radiometabolic therapy, such PET/CT with radiolabeled choline and prostate-specific membrane antigene (PSMA)-ligands, the latter being labeled either with 68Ga for imaging or with Lutetium-177 for therapy. Radium-223 dichloride has also been recently successfully introduced for palliative therapy of bone metastases in PCa. For these reasons, while the development of radiopharmaceuticals for diagnosis and therapy (theranostics concept) of neuroendocrine differentiated PCa is scientifically stimulating, the ultimate clinical impact remains presently difficult to predict. Similar effectiveness in comparison to other forms of diagnostic and radiometabolic radiopharmaceuticals that have already gained convincing acceptance among referring clinicians needs to be demonstrated.

Changes in Glucose Metabolism during and after Radiotherapy in Non-Small Cell Lung Cancer

Aims and background

Evaluation of the metabolic response to radiotherapy in non-small cell lung cancer patients is commonly performed about three months after the end of radiotherapy. The aim of the present study was to assess with positron emission tomography/computed tomography (PET/CT) and [18F]fluorodeoxyglucose changes in glucose metabolism during and after radiotherapy in non-small cell lung cancer patients.

Methods and study design

In 6 patients, PET/CT scans with [18F]fluorodeoxyglucose were performed before (PET0), during (PET1; at a median of 14 days before the end of radiotherapy) and after the end of radiotherapy (PET2 and PET3, at a median of 28 and 93 days, respectively). The metabolic response was scored according to visual and semiquantitative criteria.

Results

Standardize maximum uptake at PET1 (7.9 ± 4.8), PET2 (5.1 ± 4.1) and PET3 (2.7 ± 3.1) were all significantly (P <0.05; ANOVA repeated measures) lower than at PET0 (16.1 ± 10.1). Standardized maximum uptake at PET1 was significantly higher than at both PET2 and PET3. There were no significant differences in SUVmax between PET2 and PET3. PET3 identified 4 complete and 2 partial metabolic responses, whereas PET1 identified 6 partial metabolic responses. Radiotherapy-induced increased [18F]fluorodeoxyglucose uptake could be visually distinguished from tumor uptake based on PET/CT integration and was less frequent at PET1 (n = 2) than at PET3 (n = 6).

Conclusions

In non-small cell lung cancer, radiotherapy induces a progressive decrease in glucose metabolism that is greater 3 months after the end of treatment but can be detected during the treatment itself. Glucose avid, radiotherapy-induced inflammation is more evident after the end of radiotherapy than during radiotherapy and does not preclude the interpretation of [18F]fluorodeoxyglucose images, particularly when using PET/CT.

Role of PET/CT in the Clinical Management of Locally Advanced Pancreatic Cancer

Aim

To evaluate the role of 18F-fluorodeoxyglucose (FDG) PET/CT in: a) the selection of patients with locally advanced pancreatic cancer for helical tomotherapy with concurrent chemotherapy (HTT-ChT); b) monitoring HTT-ChT treatment efficacy in comparison with contrast-enhanced CT (c.e.CT).

Methods

Forty-two consecutive patients with unresectable locally advanced pancreatic cancer referred for HTT-ChT were enrolled in the study. All patients were pretreated with induction ChT. Before the beginning of HTT-ChT treatment patients underwent diagnostic c.e.CT (CT0) and FDG PET/CT (PET/CT0) for staging. After staging, patients received HTT-ChT. Three months after the end of HTT-ChT a control c.e.CT (CT1) was done. FDG PET/CT (PET/CT1) was repeated only in patients with positive PET/CT0. PET/CT1 and CT1 were compared with baseline imaging results to assess treatment efficacy.

Results

In 31/42 cases (74%) PET/CT0 documented pathological uptake in pancreatic lesions, while in the remaining 11/42 cases it showed no uptake. In 7/42 (17%) patients, PET/CT0 also detected distant metastases, prompting a change in the therapeutic approach. Compared to PET/CT0, PET/CT1 (n = 18) documented 3 complete metabolic responses, 9 partial metabolic responses, 2 instances of stable metabolic disease, and 4 instances of progressive metabolic disease. In the same group of 18 patients, CT1 showed 0 complete responses, 3 partial responses, 8 instances of stable disease, and 7 instances of progressive disease compared to CT0. Concordance between PET/CT and CT response was seen in 33% of cases. In 50% of cases, PET/CT1 documented a response to therapy that was not evident on CT.

Conclusions

PET/CT influenced the treatment strategy by detecting distant metastases not documented by CT, thus accurately selecting patients for HTT-ChT after induction ChT. In monitoring treatment efficacy, PET/CT can detect a metabolic response to treatment not identified by CT.

Molecular Imaging of Huntington's Disease

The onset and the clinical progression of Huntington Disease (HD) is influenced by several events prompted by a genetic mutation that affects several organs tissues including different regions of the brain. In the last decades years, Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI) helped to deepen the knowledge of neurodegenerative mechanisms that guide to clinical symptoms. Brain imaging with PET represents a tool to investigate the physiopathology occurring in the brain and it has been used to predict the age of onset of the disease and to evaluate the therapeutic efficacy of new drugs. This article reviews the contribution of PET and MRI in the research field on Huntington's disease, focusing in particular on some most relevant achievements that have helped recognize the molecular changes, the clinical symptoms and evolution of the disease. J. Cell. Physiol. 232: 1988-1993, 2017. © 2016 Wiley Periodicals, Inc.

Target Definition in Salvage Radiotherapy for Recurrent Prostate Cancer: The Role of Advanced Molecular Imaging

Salvage radiotherapy (SRT) represents the main treatment option for relapsing prostate cancer in patients after radical prostatectomy. Several open questions remain unanswered in terms of target volumes definition and delivered doses for SRT: the effective dose necessary to achieve biochemical control in the SRT setting may be different if the tumor recurrence is micro- or macroscopic. At the same time, irradiation of only the prostatic bed or of the whole pelvis will depend on the localization of the recurrence, local or locoregional. In the “theragnostic imaging” era, molecular imaging using positron emission tomography (PET) constitutes a useful tool for clinicians to define the site of the recurrence, the extent of disease, and individualize salvage treatments. The best option currently available in clinical routine is the combination of radiolabeled choline PET imaging and multiparametric magnetic resonance imaging (MRI), associating the nodal and distant metastases identification based on PET with the local assessment by MRI. A new generation of targeted tracers, namely, prostate-specific membrane antigen, show promising results, with a contrast superior to choline imaging and a higher detection rate even for low prostate-specific antigen levels; validation studies are ongoing. Finally, imaging targeting bone remodeling, using whole-body SPECT–CT, is a relevant complement to molecular/metabolic PET imaging when bone involvement is suspected.

Radiation Treatment of Lymph Node Recurrence from Prostate Cancer: Is 11C-Choline PET/CT Predictive of Survival Outcomes?

PET/CT is a valuable tool to detect lymph node (LN) metastases in patients with biochemical failure after primary treatment for prostate cancer (PCa). The aim was to assess the predictive role of imaging parameters derived by (11)C-choline PET/CT on survival outcomes-overall survival, locoregional relapse-free survival, clinical relapse-free survival (cRFS), and biochemical relapse-free survival (bRFS)-in patients treated with helical tomotherapy (HTT) for LN recurrence.

METHODS

This retrospective study included 68 patients affected by PCa (mean age, 68 y; age range, 51-81 y) with biochemical recurrence after primary treatment (median prostate-specific antigen values obtained at the time of PET/CT scan, 2.42 ng/mL; range, 0.61-27.56 ng/mL) who underwent (11)C-choline PET/CT from January 2005 to January 2013 and were treated with HTT in correspondence of the pathologic choline LN uptake. PET-derived parameters, including maximum/mean standardized uptake value (SUVmax and SUVmean, respectively) and metabolic tumor volume (MTV) with a threshold of 40%, 50%, and 60% were calculated. The best cutoff values of PET-derived parameters discriminating between patients with and without relapse, after treatment guided by PET, were assessed by receiver-operating-characteristic (ROC) curve analysis. Univariate and multivariate Cox regression analysis including the most predictive PET-derived parameters and survival outcomes were performed.

RESULTS

The median follow-up was 20 mo (mean, 26 mo; range, 3-97 mo). (11)C-choline PET/CT showed pathologic LN uptake in 4 patients at the pelvic level, in 5 at the abdominal level, in 13 at both the pelvic and the abdominal level, and in 46 at the abdominal or pelvic or other sites. The 2-y overall survival, locoregional relapse-free survival, cRFS, and bRFS were 87%, 91%, 51%, and 40%, respectively. On the basis of ROC curves, the most discriminative cutoff value for MTV values was an MTV threshold of 60% (MTV60) of greater than 0.64 cm(3). No significant cutoff values were found for SUVmax or SUVmean at univariate analysis, whereas MTV60 was confirmed as an independent predictor in multivariate analysis and significantly correlated with bRFS and cRFS. MTV60 and extrapelvic disease well predict the risk of cRFS.

CONCLUSION

(11)C-choline PET/CT performed as a guide for HTT on LN recurrence is predictive of survival. In particular, MTV60 and extrapelvic disease were the best predictors of tumor response for bRFS and cRFS in PCa patients with LN recurrence after primary treatment. This information may be useful in emerging treatment strategies.

[¹¹C]Choline PET/CT predicts survival in hormone-naive prostate cancer patients with biochemical failure after radical prostatectomy

PURPOSE

Over the last decade, PET/CT with radiolabelled choline has been shown to be useful for restaging patients with prostate cancer (PCa) who develop biochemical failure. The limitations of most clinical studies have been poor validation of [(11)C]choline PET/CT-positive findings and lack of survival analysis. The aim of this study was to assess whether [(11)C]choline PET/CT can predict survival in hormone-naive PCa patients with biochemical failure.

METHODS

This retrospective study included 302 hormone-naive PCa patients treated with radical prostatectomy who underwent [(11)C]choline PET/CT from 1 December 2004 to 31 July 2007 because of biochemical failure (prostate-specific antigen, PSA, >0.2 ng/mL). Median PSA was 1.02 ng/mL. PCa-specific survival was estimated using Kaplan-Meier curves. Cox regression analysis was used to evaluate the association between clinicopathological variables and PCa-specific survival. The coefficients of the covariates included in the Cox regression analysis were used to develop a novel nomogram.

RESULTS

Median follow-up was 7.2 years (1.4 - 18.9 years). [(11)C]Choline PET/CT was positive in 101 of 302 patients (33%). Median PCa-specific survival after prostatectomy was 14.9 years (95% CI 9.7 - 20.1 years) in patients with positive [(11)C]choline PET/CT. Median survival was not achieved in patients with negative [(11)C]choline PET/CT. The 15-year PCa-specific survival probability was 42.4% (95% CI 31.7 - 53.1%) in patients with positive [(11)C]choline PET/CT and 95.5% (95% CI 93.5 - 97.5 %) in patients with negative [(11)C]choline PET/CT. In multivariate analysis, [(11)C]choline PET/CT (hazard ratio 6.36, 95% CI 2.14 - 18.94, P < 0.001) and Gleason score >7 (hazard ratio 3.11, 95% CI 1.11 - 8.66, P = 0.030) predicted PCa-specific survival. An internally validated nomogram predicted 15-year PCa-specific survival probability with an accuracy of 80%.

CONCLUSION

Positive [(11)C]choline PET/CT after biochemical failure predicts PCa-specific survival in hormone-naive PCa patients. Prospective studies are warranted to confirm our results before more extensive use of [(11)C]choline PET/CT for prognostic stratification of PCa patients.

Relationship between prostate-specific antigen kinetics and detection rate of radiolabelled choline PET/CT in restaging prostate cancer patients: a meta-analysis

BACKGROUND

The aim of the article was to systematically review published data about the relationship between prostate-specific antigen (PSA) kinetics, including PSA doubling time (PSAdt) and PSA velocity (PSAvel), and detection rate (DR) of positron emission tomography/computed tomography (PET/CT) using radiolabelled choline in restaging prostate cancer (PCa).

METHODS

A comprehensive literature search of studies published through July 2013 regarding the relationship between PSA kinetics and DR of radiolabelled choline PET/CT was carried out. Furthermore, a meta-analysis was performed in order to establish the DR of radiolabelled choline PET/CT using different cut-off values of PSAdt (≤ or >6 months) and PSAvel [>1 or ≤1 ng/(mL year) and >2 or ≤2 ng/(mL year)]. Moreover, a pooled analysis to establish whether PSAdt and PSAvel (using the abovementioned cut-off values) may predict positive PET/CT results was carried out.

RESULTS

Fourteen articles were selected. The pooled DR of radiolabelled choline PET/CT in restaging PCa was 58% [95% confidence interval (CI) 55-60]. Most articles reported a relationship between PSA kinetics and DR of PET/CT. Pooled DR of radiolabelled choline PET/CT increased to 65% (95% CI 58-71) when PSAdt was ≤6 months and to 71% (95% CI 66-76) and 77% (95% CI 71-82) when PSAvel was >1 or >2 ng/(mL year), respectively. PSAdt ≤6 months and PSAvel >1 or >2 ng/(mL year) proved to be relevant factors in predicting the positive result of radiolabelled choline PET/CT.

CONCLUSIONS

Due to the strong relationship between PSA kinetics and DR of radiolabelled choline PET/CT, beyond PSA values, PSAdt and PSAvel should be taken into account in the selection of PCa patients who should undergo radiolabelled choline PET/CT for restaging.

(11)C-Choline PET/CT as a guide to radiation treatment planning of lymph-node relapses in prostate cancer patients

PURPOSE

To evaluate, in prostate cancer (PCa) patients the potential of (11)C-choline PET/CT as a guide to helical tomotherapy (HTT) of lymph-node (LN) relapses with simultaneous integrated boost (SIB). The efficacy and feasibility of HTT in terms of acute toxicity were assessed.

METHODS

We enrolled 83 PCa patients (mean age 68 years, range 51 - 82 years) with biochemical recurrence after radical primary treatment (mean serum PSA 7.61 ng/ml, range 0.37 - 187.00 ng/ml; PSA0) who showed pathological findings on (11)C-choline PET/CT only at the LN site. (11)C-Choline PET/CT was performed for restaging and then for radiation treatment planning (PET/CT0). Of the 83 patients, 8 experienced further LN relapse, of whom 5 were retreated once and 3 were retreated twice (total 94 radiotherapy treatments). All pelvic and/or abdominal LNs positive on PET/CT0 were treated with high doses using SIB. Doses were in the range 36 - 74 Gy administered in 28 fractions. After the end of HTT (mean 83 days, range 16 - 365 days), serum PSA was measured in all patients (PSA1) and compared with PSA0 to evaluate early biochemical response. In 47 patients PET/CT was repeated (PET/CT1) to assess metabolic responses at the treated areas. Toxicity criteria of the Radiation Therapy Oncology Group (RTOG) were used to assess acute toxicity.

RESULTS

PET/CT0 revealed pathological LNs in the pelvis in 49 patients, pathological LNs in the abdomen in 15 patients pathological LNs in both the pelvis and abdomen in 18 patients, and pathological LNs in the pelvis or abdomen and other sites in 12 patients. All these sites were treated with HTT. With respect to PSA0, PSA1 (mean 6.28 ng/ml, range 0.00 - 220.46 ng/ml) showed a complete biochemical response after 66 of the 94 HTT treatments, a partial response after 12 treatments, stable disease after 1 treatment and progression of disease after 15 treatments. Of the 47 patients receiving PET/CT1, 20 showed a complete metabolic response at the treated area, 22 a partial metabolic response, 3 progression of disease and 2 stable disease. HTT with SIB was well tolerated in all patients. Grade 3 acute toxicity in the genitourinary tract was observed in two patients.

CONCLUSION

(11)C-Choline PET/CT is a valuable tool for planning and monitoring HTT in LN relapse after primary treatment. High-dose hypofractionated (11)C-choline PET/CT-guided HTT with SIB is well tolerated and is associated with a high early biochemical response rate.

Long-term outcomes of salvage lymph node dissection for clinically recurrent prostate cancer: results of a single-institution series with a minimum follow-up of 5 years

BACKGROUND

Prostate cancer (PCa) patients with lymph node recurrence after radical prostatectomy (RP) are usually managed with androgen-deprivation therapy. Despite the absence of prospective randomized studies, salvage lymph node dissection (LND) has been proposed as an alternative treatment option.

OBJECTIVE

To examine long-term outcomes of salvage LND in patients with nodal recurrent PCa documented by 11C-choline positron emission tomography/computed tomography (PET/CT) scan.

DESIGN, SETTING, AND PARTICIPANTS

Overall, 59 patients affected by biochemical recurrence (BCR) with 11C-choline PET/CT scan with pathologic activity treated between 2002 and 2008 were included.

INTERVENTION

Pelvic and/or retroperitoneal salvage LND.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSES

Biochemical response (BR) was defined as prostate-specific antigen (PSA) <0.2 ng/ml at 40 d after surgery. BCR for those who achieved BR was defined as a PSA >0.2 ng/ml. Clinical recurrence (CR) was defined as a positive PET/CT scan after salvage LND in the presence of a rising PSA. Kaplan-Meier curves assessed time to BCR, CR, and cancer-specific mortality (CSM). Cox regression analyses were fitted to assess predictors of CR.

RESULTS AND LIMITATIONS

Median follow-up after salvage LND was 81.1 mo. Overall, 35 patients (59.3%) achieved BR. The 8-yr BCR-free survival rate in patients with complete BR was 23%. Overall, the 8-yr CR- and CSM-free survival rates were 38% and 81%, respectively. In multivariable analyses evaluating preoperative variables, PSA at salvage LND represented the only predictor of CR (p=0.03). When postoperative variables were considered, BR and the presence of retroperitoneal lymph node metastases were significantly associated with the risk of CR (all p ≤ 0.04). Our study is limited by the lack of a control group.

CONCLUSIONS

Salvage LND may represent a therapeutic option for patients with BCR after RP and nodal pathologic uptake at 11C-choline PET/CT scan. Although most patients progressed to BCR after salvage LND, roughly 40% of them experienced CR-free survival.

PATIENT SUMMARY

Salvage lymph node dissection may represent a therapeutic option for selected patients with nodal recurrence after radical prostatectomy. Roughly 40% of men did not show any further clinical recurrence at long-term follow-up after surgery.

Utility of [11C]choline PET/CT in guiding lesion-targeted salvage therapies in patients with prostate cancer recurrence localized to a single lymph node at imaging: results from a pathologically validated series

OBJECTIVE

Positron emission tomography (PET)/computed tomography (CT) has been shown to be a valid tool in detecting lymph node (LN) metastases in men with biochemical recurrence after radical prostatectomy. We assessed its validity in detecting a single positive LN at pathologic examination in regard to an increasing interest in lesion-targeted salvage therapies.

METHODS AND MATERIALS

We included 46 patients with biochemical recurrence after radical prostatectomy and a single positive spot at [(11)C]choline PET/CT who underwent pelvic or pelvic and retroperitoneal LN dissection. The ability of [(11)C]choline PET/CT in identifying the exact positive LN was assessed with the positive predictive value (PPV) in the overall population and according to androgen deprivation therapy, prostate-specific antigen value, and site of PET/CT positivity.

RESULTS

Overall, 30 patients (65%) had positive LNs at pathologic examination. Of these, only 16 (35%) had pathologically confirmed metastases in the same lymphatic region and 11 (24%) had involvement of 1 single LN. Conversely, 28 patients had positive LNs in other areas and 8 had no evidence of metastases. The overall PPV of PET/CT was 34.8% and 23.9% when exact concordance was defined according to the lymphatic landing site and single positive LN, respectively. The PPV ranged from 33.3% to 44.4% and from 17.9% to 28.6%, in men with and without androgen deprivation therapy, respectively.

CONCLUSIONS

The PPV [(11)C]choline of PET/CT in correctly identifying patients with a single positive LN at salvage LN dissection is poor (24%). Therefore, extensive salvage treatment approaches are needed to maximize the chance of cure.

Role of PET/CT in the clinical management of locally advanced pancreatic cancer

AIM

To evaluate the role of 18F-fluorodeoxyglucose (FDG) PET/CT in: a) the selection of patients with locally advanced pancreatic cancer for helical tomotherapy with concurrent chemotherapy (HTT-ChT); b) monitoring HTT-ChT treatment efficacy in comparison with contrast-enhanced CT (c.e.CT).

METHODS

Forty-two consecutive patients with unresectable locally advanced pancreatic cancer referred for HTT-ChT were enrolled in the study. All patients were pretreated with induction ChT. Before the beginning of HTT-ChT treatment patients underwent diagnostic c.e.CT (CT0) and FDG PET/CT (PET/CT0) for staging. After staging, patients received HTT-ChT. Three months after the end of HTT-ChT a control c.e.CT (CT1) was done. FDG PET/CT (PET/CT1) was repeated only in patients with positive PET/CT0. PET/CT1 and CT1 were compared with baseline imaging results to assess treatment efficacy.

RESULTS

In 31/42 cases (74%) PET/CT0 documented pathological uptake in pancreatic lesions, while in the remaining 11/42 cases it showed no uptake. In 7/42 (17%) patients, PET/CT0 also detected distant metastases, prompting a change in the therapeutic approach. Compared to PET/CT0, PET/CT1 (n = 18) documented 3 complete metabolic responses, 9 partial metabolic responses, 2 instances of stable metabolic disease, and 4 instances of progressive metabolic disease. In the same group of 18 patients, CT1 showed 0 complete responses, 3 partial responses, 8 instances of stable disease, and 7 instances of progressive disease compared to CT0. Concordance between PET/CT and CT response was seen in 33% of cases. In 50% of cases, PET/CT1 documented a response to therapy that was not evident on CT.

CONCLUSIONS

PET/CT influenced the treatment strategy by detecting distant metastases not documented by CT, thus accurately selecting patients for HTT-ChT after induction ChT. In monitoring treatment efficacy, PET/CT can detect a metabolic response to treatment not identified by CT.

[11C]choline positron emission tomography/computerized tomography for early detection of prostate cancer recurrence in patients with low increasing prostate specific antigen

PURPOSE

The effectiveness of salvage therapy in prostate cancer is greater for low prostate specific antigen values. Therefore, early detection of tumor recurrence is warranted. [(11)C]choline positron emission tomography/computerized tomography has the potential of early restaging of prostate cancer with low prostate specific antigen, but the selection of patients at high risk for positive [(11)C]choline positron emission tomography/computerized tomography is desirable to optimize salvage therapy.

MATERIALS AND METHODS

This retrospective study included 75 patients with prostate cancer with an increasing prostate specific antigen less than 1.5 ng/ml after radical prostatectomy who never received antiandrogen deprivation therapy or salvage radiotherapy who underwent [(11)C]choline positron emission tomography/computerized tomography for the restaging of disease. Binary logistic regression was used to assess predictive factors of positive [(11)C]choline positron emission tomography/computerized tomography. Included variables were trigger prostate specific antigen, prostate specific antigen doubling time, age, pathological stage and Gleason score.

RESULTS

Median prostate specific antigen was 0.61 ng/ml. [(11)C]choline positron emission tomography/computerized tomography was positive in 16 of 75 patients (21%). On univariate analysis prostate specific antigen doubling time less than 6 months was the only factor significantly associated with an increased risk of positive [(11)C]choline positron emission tomography/computerized tomography (OR 7.77, 95% CI 2.34-25.80, p = 0.001). In patients with prostate specific antigen doubling time less than 6 months, the positive detection rate of [(11)C]choline positron emission tomography/computerized tomography increased to 50%.

CONCLUSIONS

In patients with prostate cancer with biochemical failure after radical prostatectomy and prostate specific antigen less than 1.5 ng/ml, prostate specific antigen doubling time less than 6 months predicts positive [(11)C]choline positron emission tomography/computerized tomography. In these patients [(11)C]choline positron emission tomography/computerized tomography may reduce by 50% the number in whom salvage therapy is initiated empirically without knowing the disease location.

Restaging prostate cancer patients with biochemical failure with PET/CT and radiolabeled choline

PET/CT with either [11C]choline or [18F]fluorocholine represents a powerful technique for restaging prostate cancer (PCa) patients with biochemical failure. The availability of dedicated PET/CT scanners allows fusioning of morphological and functional images, which enables accurate localization of sites of pathological tracer uptake and ease the differentiation between malignant and benign findings. A noteworthy advantage of this whole-body technique is that it provides information on multiple anatomic sites at a single time. As such, the technique has the capability of distinguishing between local relapse and distant metastases, and therefore has the potential to guide the medical treatment. The positive detection rate of [11C]choline PET/CT varies substantially in relation to the inclusion criteria. Studies which included unselected consecutive patients reported a positive detection rate ranging between 40% and 70%. Serum PSA level represents the single, most important factor affecting the rate of positive scans. Other positive predicitive factors include fast PSA kinetics (PSA velocity, PSA doubling time), advanced pathological state at initial staging, previous biochemical failure, hormone resistance and older age. Recent studies indicate that [11C]choline PET/CT has the potential to early restaging PCa patients for PSA levels lower than 1-1.5 ng/mL. However, more studies are necessary to better define the potential of this technique for low PSA levels. The previously cited risk factors can be used to identify patients that are at greater risk and that might best benefit from PET/CT scans. Patients that develop biochemical failure during androgen deprivation therapy (hormone resistance) have a higher likelihood for a positive [11C]choline PET/CT scan in comparison to patients that are drug naïve (hormone sensitive) and are not required to withdraw the anti-androgenic treatment before PET/CT.

Clinical and diagnostic assessment for therapeutic decisions in prostate cancer

Due to the heterogeneity of prostate cancer (PCa) outcomes, there is a need for individualized treatment plans based on clinical and cancer characteristics. Recent advances in sophisticated imaging modalities have improved the ability to stratify patients according to their risk of PCa diagnosis and progression. This, in turn, has positively influenced the clinical decision making process. However, there is also an overuse of diagnostic imaging in the evaluation of PCa patients. Baseline diagnostic and re-staging evaluations need to be indeed personalized, in order to maximize the results and reduce unnecessary, lengthy and costly procedures. The aim of this review was to critically evaluate current international guidelines in order to identify clinical and diagnostic markers that might help clinicians in the selection of the most appropriate imaging approach. For this aim, different imaging modalities were analyzed in patients with newly diagnosed PCa, focusing on local, nodal and distant staging. Every step of staging was taken into consideration based on patient individualized risk, as defined by routinely available clinical variables. Second, different imaging techniques were also reviewed in the context of relapse after primary treatment, highlighting their utility and impact in the clinical decision making process. This review focuses mainly on conventional established imaging techniques, with an eye also to novel approaches that still need to be validated on large patient series.

Effect of amino acid infusion on potassium serum levels in neuroendocrine tumour patients treated with targeted radiopeptide therapy

PURPOSE

Administration of positively charged amino acids has been introduced to reduce the nephrotoxicity of targeted radiopeptide therapy (TRT). However, the amino acid solution may have side effects, including hyperkalaemia. The aim of this study was to evaluate the frequency and the magnitude of hyperkalaemia in neuroendocrine tumour (NET) patients undergoing TRT.

METHODS

Enrolled in the study were 31 patients with NET eligible for TRT with [(90)Y-DOTA(0),Tyr(3)]octreotide ((90)Y-DOTATOC). Their mean age was 54 ± 14 years. Of these 31 patients, 21 (67%) were referred for the first treatment cycle, while 10 (33%) were referred for a subsequent therapy cycle. Patients were treated with therapeutic doses of (90)Y-DOTATOC ranging from 7,030 to 35,520 MBq. To inhibit tubular reabsorption of (90)Y-DOTATOC, 1 l of physiological saline solution containing 25 g of arginine hydrochloride and 25 g of lysine hydrochloride was given over 4 h starting 1 h before (90)Y-DOTATOC injection. All patients underwent a standard biochemical blood analysis at baseline, and 4 h and 24 h after the beginning of the amino acid infusion.

RESULTS

ANOVA repeated measures showed a significant overall effect on K(+) levels over time (F = 118.2, df = 2, P < 0.0001). Mean serum levels of K(+) were 4.00 ± 0.33 mmol/l at baseline, 5.47 ± 0.57 mmol/l at 4 h, and 4.38 ± 0.63 mmol/l at 24 h after the beginning of the infusion. Post-hoc analysis showed that K(+) levels at 4 h were significantly (P < 0.05) higher than at baseline. K(+) levels at 24 h were significantly (P < 0.05) lower than at 4 h but they were still significantly (P < 0.05) higher than K(+) levels at baseline. On a subject-by-subject basis, none of the 31 patients had increased K(+) levels at baseline. At 4 h, 24 of the 31 patients (77%) had K(+) levels above the normal range, and 6 patients (19%) experienced severe hyperkalaemia (K(+) ≥ 6 mmol/l). All patients with increased K(+) levels were clinically asymptomatic. At 24 h, only 4 patients (13%) had increased K(+) serum levels. The magnitude of the increase in K(+) levels between baseline and 4 h was relatively homogeneous over the whole group (1.41 ± 0.50 mmol/l) and it was not related (linear regression, P>0.05) to baseline K(+) levels. Intravenous administration of 40 mg furosemide 1 h after the beginning of the amino acid infusion did not have a significant effect on K(+) levels (P>0.05). No clinical characteristic was predictive for the increase in K(+) levels (chi-squared test, P > 0.05).

CONCLUSION

Hyperkalaemia is a frequent, potentially life-threatening side effect of basic amino acid infusion during TRT. K(+) levels 4 h after the beginning of the infusion should be monitored in patients at risk of complications, such as those with heart disease and those with risk factors for nephrotoxicity.

Targeted radiotherapy with radiolabeled somatostatin analogs

Targeted radiopeptide therapy with (90)Yttrium- or (177)Lutetium-labeled somatostatin analogs has been proven to improve significantly quality of life and survival in patients suffering from metastatic or unresectable neuroendocrine tumors (NETs). Roughly 25% of patients achieve partial remission; progression-free survival is estimated to be 30 to 40 months. A wide range of protocols using different somatostatin analogs, isotopes, injected activity per cycle of administration, and number of cycles are reported. More patient-based therapy protocols are under development, taking into consideration the complexity of NET cell biology, dosimetric issues, and the availability of different radiolabeled analogs. This article reviews the effectiveness and safety of the different protocols and discusses several clinical algorithms used in an attempt to optimize targeted radiopeptide therapy.

[11C]choline positron emission tomography/computerized tomography to restage prostate cancer cases with biochemical failure after radical prostatectomy and no disease evidence on conventional imaging

PURPOSE

We assessed the value of [11C]choline positron emission tomography/computerized tomography in patients with prostate cancer in whom biochemical failure developed after radical prostatectomy but who showed no disease evidence on conventional imaging.

MATERIALS AND METHODS

Considered for this study were 2,124 patients treated with radical prostatectomy who underwent [11C]choline positron emission tomography/computerized tomography to restage disease between December 2004 and January 2007. Study inclusion criteria were 1) previous radical prostatectomy and pelvic lymph node dissection, 2) increasing prostate specific antigen beyond 0.2 ng/ml after radical prostatectomy, 3) no lymph node disease at radical prostatectomy, 4) no evidence of metastatic disease on conventional imaging, 5) no androgen deprivation therapy and 6) no adjuvant or salvage radiotherapy. These criteria were satisfied in 109 of the 2,124 patients (5%).

RESULTS

Median prostate specific antigen at imaging was 0.81 ng/ml (range 0.22 to 16.76 ml). Imaging suggested local recurrence in 4 patients (4%) and pelvic lymph node disease in 8 (7%). Scans were positive in 5%, 15% and 28% of patients with prostate specific antigen less than 1, between 1 and 2, and greater than 2 ng/ml, respectively (p <0.05). Prostate specific antigen was the only significant predictor of tomography results (p <0.05).

CONCLUSIONS

Positron emission tomography/computerized tomography detected increased [11C]choline uptake, suggesting recurrent disease in 11% of patients with prostate cancer, increasing prostate specific antigen after radical prostatectomy and no evidence of disease on conventional imaging. This modality may be useful to restage disease but it cannot be used to guide therapy.

Using cerebral white matter for estimation of nondisplaceable binding of 5-HT1A receptors in temporal lobe epilepsy

The estimation of nondisplaceable binding from cerebellar white matter, rather than from whole cerebellum, was proposed for the PET tracer carbonyl-(11)C-WAY-100635 (N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl}-N-(2-pyridyl)cyclohexanecarboxamidel]) because of the heterogeneity of total ligand binding in this region. For the 5-hydroxytryptamine receptor 1A (5-HT(1A)) antagonist (18)F-N-{2-[4-(2-methoxyphenyl)piperazin-1-yl]ethyl}-N-2-pyridyl)trans-4-fluorocyclohexanecarboxamide ((18)F-FCWAY), the estimation of nondisplaceable binding from cerebellum (V(ND)) may be additionally biased by spillover of (18)F-fluoride activity from skull. We aimed to assess the effect of using cerebral white matter as reference region on detection of group differences in 5-HT(1A) binding with PET and (18)F-FCWAY.

METHODS

In 22 temporal lobe epilepsy patients (TLE) and 10 healthy controls, (18)F-FCWAY distribution volume in cerebral white matter (V(WM)) was computed using an extrapolation method as part of a partial-volume correction (PVC) algorithm. To assess the feasibility of applying this method to clinical studies in which PVC is not performed, V(WM) was also calculated by placing circular, 6-mm-diameter regions of interest (ROIs) in the centrum semiovalis on parametric images. Binding potentials were BP(F) = (V(T) - V(ND))/f(P) and BP(F-WM) = (V(T) - V(WM))/f(P), where V(T) is total distribution volume and f(P) = (18)F-FCWAY plasma free fraction. Statistical analysis was performed using t tests and linear regression.

RESULTS

In the whole group, V(WM) was 14% +/- 19% lower than V(ND) (P < 0.05). V(WM)/f(P) was significantly (P < 0.05) lower in patients than in controls. All significant (P < 0.05) reductions of 5-HT(1A) receptor availability in TLE patients detected by BP(F) were also detected using BP(F-WM). Significant (P < 0.05) reductions of 5-HT(1A) specific binding were detected by BP(F-WM), but not BP(F), in ipsilateral inferior temporal cortex, contralateral fusiform gyrus, and contralateral amygdala. However, effect sizes were similar for BP(F-WM) and BP(F). The value of V(WM) calculated with the ROI approach did not significantly (P > 0.05) differ from that calculated with the extrapolation approach (0.67 +/- 0.32 mL/mL and 0.72 +/- 0.34 mL/mL, respectively).

CONCLUSION

Cerebral white matter can be used for the quantification of nondisplaceable binding of 5-HT(1A) without loss of statistical power for detection of regional group differences. The ROI approach is a good compromise between computational complexity and sensitivity to spillover of activity, and it appears suitable to studies in which PVC is not performed. For (18)F-FCWAY, this approach has the advantage of avoiding spillover of (18)F-fluoride activity onto the reference region.

Incidental detection by [11C]choline PET/CT of meningiomas in prostate cancer patients

AIM

Anti-androgenic hormonal therapy in prostate cancer patients with concomitant meningioma may result in tumor growth and development of neurological symptoms. Positron emission tomography/computed tomography (PET/CT) with [11C]choline is used for restaging prostate cancer patients with biochemical failure. In vitro and in vivo data support altered choline metabolism in meningiomas.

METHODS

During a retrospective study in prostate cancer patients with biochemical failure referred to our institution between November 2004 and January 2007, encephalic focal uptake of [11C]choline was incidentally noted in 4 patients, 2 of which had been taking luteinizing hormone-releasing hormone analogs.

RESULTS

Subsequent to the incidental finding, one patient underwent surgical removal of the meningioma; strict neuroradiological follow-up was planned for the 3 other patients.

CONCLUSION

We suggest that in prostate cancer patients candidate for anti-androgenic therapy the whole body [11C]choline PET/CT scan should include the whole skull to check for the possible presence of meningiomas. This could help to identify patients at risk for the development of neurological symptoms during anti-androgenic therapy and help the referring urologist in the clinical management of these patients.

Positron emission tomography/computed tomography introduction in the clinical management of patients with suspected recurrence of ovarian cancer: a cost-effectiveness analysis

Aim of this study was to evaluate the economic impact of the introduction of positron emission tomography/computed tomography (PET/CT) in the early detection of recurrent ovarian cancer through a cost-effectiveness analysis of different diagnostic strategies. Thirty-two consecutive patients with suspected ovarian cancer recurrence, studied by both contrast enhanced abdominal CT and PET/CT, were retrospectively included in the study. Three different diagnostic strategies were evaluated and compared: (1) CT only or baseline strategy; (2) PET/CT for negative CT or strategy A; (3) PET/CT for All or strategy B. For each one, expected costs, avoided surgery and incremental cost-effectiveness ratio (ICER) were calculated to identify the most cost-effective strategy. The number of positive patients increased from baseline strategy (20/32) to strategy A and B (30/32 and 29/32 respectively). Positron emission tomography/computed tomography reoriented physician choice in 31% and 62% of patients (strategies A and B respectively). Strategy A is dominated by strategy B, which is more expensive (2909 euro vs. 2958 euro), but also more effective (3 cases of surgery avoided) and presents an ICER of 226.77 euro per surgery avoided (range: 49.50-433.00 euro). Positron emission tomography/computed tomography introduction in this population is cost-effective and allowed to redirect the clinical management of patients towards more appropriate therapeutic choices.

Role of 18FDG-PET/CT in detecting relapse during follow-up of patients with Hodgkin's lymphoma

The role of 18FDG-PET/CT during follow-up of patients affected by Hodgkin's lymphoma (HL) in complete remission after treatment is not fully elucidated, since a wide use of 18F fluorodeoxyglucose positron emission tomography/computed tomography (18FDG-PET/CT) in this setting could be limited by a relative high rate of false-positive results. Herein, we summarize a retrospective analysis of 27 patients with Hodgkin's lymphoma in complete remission after the first-line (n = 20) or salvage (n = 7) therapy receiving serial 18FDG-PET/CT scans during follow-up. Out of 165 scans, 13 were suspected for relapse, which was confirmed in seven patients. All relapses were correctly identified by 18FDG-PET/CT positivity, with a 100% sensitivity; false-positive rate was 46% and negative predictive value was 100%. True-positive findings were mostly associated with multiple sites, subdiaphragmatic involvement, and/or previous sites of disease. According to our results, we conclude that performing routine PET/CT scan during follow-up of those patients who are at high risk of relapse would be advisable, although caution must be adopted when interpreting PET/CT results due to the relatively high rate of false-positive findings. If FDG abnormal uptake is present at multiple nodal sites, subdiaphragmatic lymph nodes, or previous sites of disease, histological verification of PET abnormal findings is warranted.

PET-CT for treatment planning in prostate cancer

Molecular imaging techniques, such as positron emission tomography (PET), may be of help in management treatment planning. In particular, in prostate cancer patients, PET and PET-computed tomography (PET-CT) can be successfully used in treatment planning at different steps, including: 1) tumor characterization and staging, to define the most appropriate primary treatment; 2) re-staging, to define a second line therapy on the site of possible recurrences; and 3) monitoring the disease and the efficacy of treatment. Although the most commonly used PET tracer, [(18)F]Fluorodeoxyglucose ([(18)F]FDG), presents limitations in imaging prostate cancer patients, several alternative PET tracers have been proposed to evaluate by PET these patients, with promising

RESULTS

Optimal treatment for prostate cancer depends on the accuracy in tumor characterization and staging. In fact, localized primary tumor can be treated with radical prostatectomy, while metastatic tumor is usually treated with systemic therapeutic regimen. Different PET tracers, including [(11)C]Choline, [(18)F]Choline and [(11)C]Acetate, have been successfully reported. Howe-ver, further studies in large population of patients are still necessary to establish their final clinical role in the primary detection and staging of prostate cancer. The information on the site of possible recurrences is also important for therapeutic strategies. Several PET tracers have been proposed to re-stage prostate cancer patients. In particular, [11C]Choline PET has now been established as a clinical procedure to non-invasively re-stage, in a single session, prostate cancer patients presenting an increase of prostate specific antigen (PSA) after radical treatment. The role of PET and PET-CT in monitoring the disease and the effects of treatment are under investigation and still to be defined. In the present review, we focused on the use of several PET tracers in different clinical indications aimed at the treatment planning of prostate cancer patients.

Riluzole protects Huntington disease patients from brain glucose hypometabolism and grey matter volume loss and increases production of neurotrophins

PURPOSE

Huntington disease (HD) mutation increases gain-of-toxic functions contributing to glutamate-mediated excitotoxicity. Riluzole interferes with glutamatergic neurotransmission, thereby reducing excitotoxicity, enhancing neurite formation in damaged motoneurons and increasing serum concentrations of BDNF, a brain cortex neurotrophin protecting striatal neurons from degeneration.

METHODS

We investigated metabolic and volumetric differences in distinct brain areas between 11 riluzole-treated and 12 placebo-treated patients by MRI and (18)F-fluoro-2-deoxy-D-glucose (FDG) PET scanning, according to fully automated protocols. We also investigated the influence of riluzole on peripheral growth factor blood levels.

RESULTS

Placebo-treated patients showed significantly greater proportional volume loss of grey matter and decrease in metabolic FDG uptake than patients treated with riluzole in all cortical areas (p<0.05). The decreased rate of metabolic FDG uptake correlated with worsening clinical scores in placebo-treated patients, compared to those who were treated with riluzole. The progressive decrease in metabolic FDG uptake observed in the frontal, parietal and occipital cortex correlated linearly with the severity of motor scores calculated by Unified Huntington Disease Rating Scale (UHDRS-I) in placebo-treated patients. Similarly, the rate of metabolic changes in the frontal and temporal areas of the brain cortex correlated linearly with worsening behavioural scores calculated by UHDRS-III in the placebo-treated patients. Finally, BDNF and transforming growth factor beta-1 serum levels were significantly higher in patients treated with riluzole.

CONCLUSION

The linear correlation between decreased metabolic FDG uptake and worsening clinical scores in the placebo-treated patients suggests that FDG-PET may be a valuable procedure to assess brain markers of HD.

C-11 choline versus F-18 fluorodeoxyglucose for imaging meningiomas: an initial experience

PURPOSE

Positron emission tomography/computed tomography (PET/CT) with C-11 choline has been used for staging, restaging, and follow-up of various tumors, whereas its role for imaging meningiomas has only been preliminarily explored. The aim of this study was to compare C-11 choline and F-18 fluorodeoxyglucose (F-18 FDG) uptake in meningiomas and relate these findings to the histopathological analysis.

METHODS

Two sequential three-dimensional PET/CT scans with 370 MBq (10 mCi) of C-11 choline and 370 MBq (10 mCi) of F-18 FDG were performed 2 hours apart in 7 patients with histologically confirmed meningiomas. Five patients had WHO grade I and 2 had WHO grade II meningioma. For each scan, two-dimensional regions of interest were drawn on tumor boundaries and on the contralateral side on CT images and copied to the corresponding PET images. SUVmax and tumor-to-background ratio were calculated.

RESULTS

Relative to the contralateral side, C-11 choline uptake was increased in all meningiomas, whereas F-18 FDG uptake was decreased in 6 patients and increased in 1 of the 2 patients with grade II meningiomas. In the whole group, SUVmax of C-11 choline and F-18 FDG were 3.6 +/- 1.3 and 5.7 +/- 1.3, respectively. The tumor-to-background ratio for C-11 choline was much higher than that for F-18 FDG (5.3 +/- 0.8 vs. 0.9 +/- 0.2, respectively) (P < 0.001). The uptake of C-11 choline was higher in patients with grade II than in grade I meningiomas.

CONCLUSIONS

These preliminary results suggest that C-11 choline may better image meningiomas in comparison with F-18 FDG. Clinical applications of C-11 choline PET/CT for grading and follow-up of meningiomas need to be assessed in further studies.

18F-FCWAY and 18F-FDG PET in MRI-negative temporal lobe epilepsy

BACKGROUND

Positron emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) shows widespread hypometabolism even in temporal lobe epilepsy (TLE) patients with mesial temporal foci. (18)F-trans-4-fluoro-N-2-[4-(2-methoxyphenyl) piperazin-1-yl]ethyl-N-(2-pyridyl)cyclohexane carboxamide ((18)F-FCWAY) PET may show more specific 5-HT(1A)-receptor binding reduction in seizure initiation than in propagation regions. (18)FCWAY PET might be valuable for detecting epileptic foci, and distinguishing mesial from lateral temporal foci in MRI-negative patients with TLE.

METHODS

We performed (18)F-FCWAY-PET and (18)F-FDG-PET in 12 MRI-negative TLE patients who had had either surgery or subdural electrode recording, and 15 healthy volunteers. After partial volume correction for brain atrophy, free fraction-corrected volume of distribution (V/f1) measurement and asymmetry indices (AIs) were computed. We compared (18)F-FCWAY-PET and (18)F-FDG-PET results with scalp video electroencephalography (EEG), invasive EEG, and surgical outcome.

RESULTS

Mean (18)F-FCWAY V/f1, compared with normal controls, was decreased significantly in fusiform gyrus, hippocampus, and parahippocampus ipsilateral to epileptic foci, and AIs were significantly greater in hippocampus, parahippocampus, fusiform gyrus, amygdala, and inferior temporal regions. Eleven patients had clearly lateralized epileptogenic zones. Nine had congruent, and two nonlateralized, (18)F-FCWAY PET. One patient with bitemporal seizure onset had nonlateralized (18)F-FCWAY-PET. (18)F-FDG-PET showed congruent hypometabolism in 7 of 11 EEG-lateralized patients, bilateral hypometabolic regions in one, contralateral hypometabolism in one, as well as lateralized hypometabolism in the patient with bitemporal subdural seizure onset. Patients with mesial temporal foci tended to have lower superior and midtemporal (18)F-FCWAY V/f1 binding AI than those with lateral or diffuse foci.

CONCLUSION

(18)F-FCWAY-PET can detect reduced binding in patients with normal MRI, and may be more accurate than (18)F-FDG-PET.

Imaging neuroinflammation in Alzheimer's disease with radiolabeled arachidonic acid and PET

Incorporation coefficients (K*) of arachidonic acid (AA) in the brain are increased in a rat model of neuroinflammation, as are other markers of AA metabolism. Data also indicate that neuroinflammation contributes to Alzheimer's disease (AD). On the basis of these observations, K* for AA was hypothesized to be elevated in patients with AD.

METHODS

A total of 8 patients with AD with an average (+/-SD) Mini-Mental State Examination score of 14.7+/-8.4 (mean age, 71.7+/-11.2 y) and 9 controls with a normal Mini-Mental State Examination score (mean age, 68.7+/-5.6 y) were studied. Each subject received a (15)O-water PET scan of regional cerebral blood flow, followed after 15 min by a 1-(11)C-AA scan of regional K* for AA.

RESULTS

In the patients with AD, compared with control subjects, global gray matter K* for AA (corrected or uncorrected for the partial-volume error [PVE]) was significantly elevated, whereas only PVE-uncorrected global cerebral blood flow was reduced significantly (P<0.05). A false-discovery-rate procedure indicated that PVE-corrected K* for AA was increased in 78 of 90 identified hemispheric gray matter regions. PVE-corrected regional cerebral blood flow, although decreased in 12 regions at P<0.01 by an unpaired t test, did not survive the false-discovery-rate procedure. The surviving K* increments were widespread in the neocortex but were absent in caudate, pallidum, and thalamic regions.

CONCLUSION

These preliminary results show that K* for AA is widely elevated in the AD brain, particularly in regions reported to have high densities of senile (neuritic) plaques with activated microglia. To the extent that the elevations represent upregulated AA metabolism associated with neuroinflammation, PET with 1-(11)C-AA could be used to examine neuroinflammation in patients with AD and other brain diseases.