Clinical role of positron emission tomography in oncology

Common anesthetic used in preclinical PET imaging inhibits metabolism of the PET tracer [18F]3F4AP

Positron emission tomography (PET) imaging studies in laboratory animals are almost always performed under isoflurane anesthesia to ensure that the subject stays still during the image acquisition. Isoflurane is effective, safe, and easy to use, and it is generally assumed to not have an impact on the imaging results. Motivated by marked differences observed in the brain uptake and metabolism of the PET tracer 3-[18F]fluoro-4-aminopyridine [(18F]3F4AP) between human and nonhuman primate studies, this study investigates the possible effect of isoflurane on this process. Mice received [18F]3F4AP injection while awake or under anesthesia and the tracer brain uptake and metabolism was compared between groups. A separate group of mice received the known cytochrome P450 2E1 inhibitor disulfiram prior to tracer administration. Isoflurane was found to largely abolish tracer metabolism in mice (74.8 ± 1.6 vs. 17.7 ± 1.7% plasma parent fraction, % PF) resulting in a 4.0-fold higher brain uptake in anesthetized mice at 35 min post-radiotracer administration. Similar to anesthetized mice, animals that received disulfiram showed reduced metabolism (50.0 ± 6.9% PF) and a 2.2-fold higher brain signal than control mice. The higher brain uptake and lower metabolism of [18F]3F4AP observed in anesthetized mice compared to awake mice are attributed to isoflurane's interference in the CYP2E1-mediated breakdown of the tracer, which was confirmed by reproducing the effect upon treatment with the known CYP2E1 inhibitor disulfiram. These findings underscore the critical need to examine the effect of isoflurane in PET imaging studies before translating tracers to humans that will be scanned without anesthesia.

CT-guided percutaneous transthoracic needle biopsy for anterior mediastinal lymphoma: the role of PET/CT

BACKGROUND

Computed tomography (CT)-guided percutaneous transthoracic needle biopsy (PTNB) is not recommended as the diagnostic modality of choice for anterior mediastinal lymphoma, despite its advantages of minimal invasiveness and easy accessibility.

PURPOSE

To identify the modifiable risk factors for non-diagnostic results from CT-guided PTNB for anterior mediastinal lymphoma.

MATERIAL AND METHODS

This retrospective study identified CT-guided PTNB for anterior mediastinal lesions diagnosed as lymphoma between May 2007 and December 2021. The diagnostic sensitivity and complications were investigated. The appropriateness of PTNB targeting was evaluated using positron emission tomography (PET)/CT and images from intra-procedural CT-guided PTNB. Targeting was considered inappropriate when the supposed trajectory of the cutting needle was within a region of abnormally low metabolism. The risk factors for non-diagnostic results were determined using logistic regression analysis.

RESULTS

A total of 67 PTNBs in 60 patients were included. The diagnostic sensitivity for lymphoma was 76.1% (51/67), with an immediate complication rate of 4.5% (3/67). According to the PET/CT images, PTNB targeting was inappropriate in 10/14 (71.4%) of the non-diagnostic PTNBs but appropriate in all diagnostic PTNBs (P <0.001). Inappropriate targeting was the only significant risk factor for non-diagnostic results (odds ratio = 203.69; 95% confidence interval = 8.17-999.99; P = 0.001). The number of specimen acquisitions was not associated with non-diagnostic results (P = 0.40).

CONCLUSIONS

Only inappropriate targeting of the non-viable portion according to PET/CT was an independent risk factor for non-diagnostic results. Acquiring PET/CT scans before biopsy and targeting the viable portion on PET/CT may help improve the diagnostic sensitivity of PTNB.

Circular RNA-mediated miRNA sponge & RNA binding protein in biological modulation of breast cancer

Circular RNAs (circRNAs) and small non-coding RNAs of the head-to-junction circle in the construct play critical roles in gene regulation and are significantly associated with breast cancer (BC). Numerous circRNAs are potential cancer biomarkers that may be used for diagnosis and prognosis. Widespread expression of circRNAs is regarded as a feature of gene expression in highly diverged eukaryotes. Recent studies show that circRNAs have two main biological modulation models: sponging and RNA-binding. This review explained the biogenesis of circRNAs and assessed emerging findings on their sponge function and role as RNA-binding proteins (RBPs) to better understand how their interaction alters cellular function in BC. We focused on how sponges significantly affect the phenotype and progression of BC. We described how circRNAs exercise the translation functions in ribosomes. Furthermore, we reviewed recent studies on RBPs, and post-protein modifications influencing BC and provided a perspective on future research directions for treating BC.

Hypothetical biosynthetic pathways of pharmaceutically potential hallucinogenic metabolites in Myristicaceae, mechanistic convergence and co-evolutionary trends in plants and humans

The family Myristicaceae harbour mind-altering phenylpropanoids like myristicin, elemicin, safrole, tryptamine derivatives such as N,N-dimethyltryptamine (DMT) and 5-methoxy N,N-dimethyltryptamine (5-MeO-DMT) and β-carbolines such as 1-methyl-6-methoxy-dihydro-β-carboline and 2-methyl-6-methoxy-1,2,3,4-tetrahydro-β-carboline. This study aimed to systematically review and propose the hypothetical biosynthetic pathways of hallucinogenic metabolites of Myristicaceae which have the potential to be used pharmaceutically. Relevant publications were retrieved from online databases, including Google Scholar, PubMed Central, Science Direct and the distribution of the hallucinogens among the family was compiled. The review revealed that the biosynthesis of serotonin in plants was catalysed by tryptamine 5-hydroxylase (T5H) and tryptophan 5-hydroxylase (TPH), whereas in invertebrates and vertebrates only by tryptophan 5-hydroxylase (TPH). Indolethylamine-N-methyltransferase catalyses the biosynthesis of DMT in plants and the brains of humans and other mammals. Caffeic acid 3-O-methyltransferase catalyses the biosynthesis of both phenylpropanoids and tryptamines in plants. All the hallucinogenic markers exhibited neuropsychiatric effects in humans as mechanistic convergence. The review noted that DMT, 5-MeO-DMT, and β-carbolines were natural protectants against both plant stress and neurodegenerative human ailments. The protein sequence data of tryptophan 5-hydroxylase and tryptamine 5-hydroxylase retrieved from NCBI showed a co-evolutionary relationship in between animals and plants on the phylogenetic framework of a Maximum Parsimony tree. The review also demonstrates that the biosynthesis of serotonin, DMT, 5-MeO-DMT, 5-hydroxy dimethyltryptamine, and β-carbolines in plants, as well as endogenous secretion of these compounds in the brain and blood of humans and rodents, reflects co-evolutionary mutualism in plants and humans.

Common anesthetic used in preclinical PET imaging inhibits metabolism of the PET tracer [ 18 F]3F4AP

PET imaging studies in laboratory animals are almost always performed under isoflurane anesthesia to ensure that the subject stays still during the image acquisition. Isoflurane is effective, safe, and easy to use, and it is generally assumed to not have an impact on the imaging results. Motivated by marked differences observed in [ 18 F]3F4AP brain uptake and metabolism between human and nonhuman primate studies, this study investigates the possible effect of isoflurane on [ 18 F]3F4AP metabolism and brain uptake. Isoflurane was found to largely abolish tracer metabolism in mice resulting in a 3.3-fold higher brain uptake in anesthetized mice at 35 min post radiotracer administration, which replicated the observed effect in unanesthetized humans and anesthetized monkeys. This effect is attributed to isoflurane's interference in the CYP2E1-mediated breakdown of [ 18 F]3F4AP, which was confirmed by reproducing a higher brain uptake and metabolic stability upon treatment with the known CYP2E1 inhibitor disulfiram. These findings underscore the critical need to examine the effect of isoflurane in PET imaging studies before translating tracers to humans that will be scanned without anesthesia.

Dose reduction in dynamic synaptic vesicle glycoprotein 2A PET imaging using artificial neural networks

Objective. Reducing dose in positron emission tomography (PET) imaging increases noise in reconstructed dynamic frames, which inevitably results in higher noise and possible bias in subsequently estimated images of kinetic parameters than those estimated in the standard dose case. We report the development of a spatiotemporal denoising technique for reduced-count dynamic frames through integrating a cascade artificial neural network (ANN) with the highly constrained back-projection (HYPR) scheme to improve low-dose parametric imaging.Approach. We implemented and assessed the proposed method using imaging data acquired with11C-UCB-J, a PET radioligand bound to synaptic vesicle glycoprotein 2A (SV2A) in the human brain. The patch-based ANN was trained with a reduced-count frame and its full-count correspondence of a subject and was used in cascade to process dynamic frames of other subjects to further take advantage of its denoising capability. The HYPR strategy was then applied to the spatial ANN processed image frames to make use of the temporal information from the entire dynamic scan.Main results. In all the testing subjects including healthy volunteers and Parkinson's disease patients, the proposed method reduced more noise while introducing minimal bias in dynamic frames and the resulting parametric images, as compared with conventional denoising methods.Significance. Achieving 80% noise reduction with a bias of -2% in dynamic frames, which translates into 75% and 70% of noise reduction in the tracer uptake (bias, -2%) and distribution volume (bias, -5%) images, the proposed ANN+HYPR technique demonstrates the denoising capability equivalent to a 11-fold dose increase for dynamic SV2A PET imaging with11C-UCB-J.

HER2 low expression breast cancer subtyping and their correlation with prognosis and immune landscape based on the histone modification related genes

Human epidermal growth factor receptor 2 (HER2) plays an important role in diagnosis and treatment of breast cancer (BRCA). The histone modification has been found to be related to the progression of cancer. This study aimed to probe the low HER2 expression BRCA heterogeneity by histone modification genes. The BRCA data and cell lines were collected from The Cancer Genome Atlas database. Weighted gene co-expression network analysis and non-negative matrix factorization clustering were jointly applied to obtain BRCA clusters. The expression of hub histone modification gene was detected using western blot assay. The gene ontology term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were performed to reveal functional information. The overall survival analysis was performed using survival and survminer packages, and the immune landscape was mainly analyzed using CIBERSORT software. Totally 43 histone modification genes correlated with survival of BRCA patients with HER2 low expression were screened. Based on these 43 histone modification genes, the BRCA samples were classified into cluster1, cluster2 and cluster3. Histone modification gene NFKBIZ exhibited high expression, while RAD51 demonstrated low expression in low HER2 expression BRCA cell. Cluster1 exhibited the best prognosis, while cluster3 had the worse outcomes. Tumor mutational burden (TMB) was remarkably increased in cluster3 group compared to cluster1 and cluster2. Moreover, the relative proportion of 16 immune cell infiltration and 8 immune checkpoint expression were remarkably differential among cluster1, cluster2 and cluster3, and the drug sensitivity exhibited difference among cluster1, cluster2 and cluster3 in BRCA patients with low HER2 expression. This study identified three HER2 low expression BRCA clusters with different characteristics based on histone modification genes. The TMB, immune cell infiltration, immune checkpoints and drug sensitivity were different among the three clusters.

Superiority of [11C]methionine over [18F]deoxyglucose for PET Imaging of Multiple Cancer Types Due to the Methionine Addiction of Cancer

Positron emission tomography (PET) is widely used to detect cancers. The usual isotope for PET imaging of cancer is [¹⁸F]deoxyglucose. The premise of using [¹⁸F]deoxyglucose is that cancers are addicted to glucose (The Warburg effect). However, cancers are more severely addicted to methionine (The Hoffman effect). [¹¹C]methionine PET (MET-PET) has been effectively used for the detection of glioblastoma and other cancers in the brain, and in comparison, MET-PET has been shown to be more sensitive and accurate than [¹⁸F]deoxyglucose PET (FDG-PET). However, MET-PET has been limited to cancers in the brain. The present report describes the first applications of MET-PET to cancers of multiple organs, including rectal, bladder, lung, and kidney. The results in each case show that MET-PET is superior to FDG-PET due to the methionine addiction of cancer and suggest that the broad application of MET-PET should be undertaken for cancer detection.

Fluorodeoxyglucose-positron emission tomography as a potential alternative tool for functional diagnosis of glycogen storage disease type I

A 43-year-old woman with genetically confirmed glycogen storage disease type Ib was suspected to have left breast cancer. Fluorodeoxyglucose-positron emission tomography showed high fluorodeoxyglucose accumulation in the whole liver as well as left mammary gland. We consider that high fluorodeoxyglucose accumulation in the liver of patients with glycogen storage disease type I is caused by impaired glucose-6-phosphate metabolism due to the congenital deficiency of glucose-6-phosphatase activities in hepatocytes. This study describes fluorodeoxyglucose-positron emission tomography as a potential alternative tool to diagnose glycogen storage disease type I functionally.

Dialysis as a Novel Adjuvant Treatment for Malignant Cancers

Simple Summary

There is a clear need for new cancer therapies as many cancers have a very short long-term survival rate. For most advanced cancers, therapy resistance limits the benefit of any single-agent chemotherapy, radiotherapy, or immunotherapy. Cancer cells show a greater dependence on glucose and glutamine as fuel than healthy cells do. In this article, we propose using 4- to 8-h dialysis treatments to change the blood composition, i.e., lowering glucose and glutamine levels, and elevating ketone levels—thereby disrupting major metabolic pathways important for cancer cell survival. The dialysis’ impact on cancer cells include not only metabolic effects, but also redox balance, immunological, and epigenetic effects. These pleiotropic effects could potentially enhance the effectiveness of traditional cancer treatments, such as radiotherapies, chemotherapies, and immunotherapies—resulting in improved outcomes and longer survival rates for cancer patients.

Abstract

Cancer metabolism is characterized by an increased utilization of fermentable fuels, such as glucose and glutamine, which support cancer cell survival by increasing resistance to both oxidative stress and the inherent immune system in humans. Dialysis has the power to shift the patient from a state dependent on glucose and glutamine to a ketogenic condition (KC) combined with low glutamine levels—thereby forcing ATP production through the Krebs cycle. By the force of dialysis, the cancer cells will be deprived of their preferred fermentable fuels, disrupting major metabolic pathways important for the ability of the cancer cells to survive. Dialysis has the potential to reduce glucose levels below physiological levels, concurrently increase blood ketone body levels and reduce glutamine levels, which may further reinforce the impact of the KC. Importantly, ketones also induce epigenetic changes imposed by histone deacetylates (HDAC) activity (Class I and Class IIa) known to play an important role in cancer metabolism. Thus, dialysis could be an impactful and safe adjuvant treatment, sensitizing cancer cells to traditional cancer treatments (TCTs), potentially making these significantly more efficient.

Targeting Glucose Metabolism Enzymes in Cancer Treatment: Current and Emerging Strategies

Simple Summary

Reprogramming of glucose metabolism is a hallmark of cancer and can be targeted by therapeutic agents. Some metabolism regulators, such as ivosidenib and enasidenib, have been approved for cancer treatment. Currently, more advanced and effective glucose metabolism enzyme-targeted anticancer drugs have been developed. Furthermore, some natural products have shown efficacy in killing tumor cells by regulating glucose metabolism, offering novel therapeutic opportunities in cancer. However, most of them have failed to be translated into clinical applications due to low selectivity, high toxicity, and side effects. Recent studies suggest that combining glucose metabolism modulators with chemotherapeutic drugs, immunotherapeutic drugs, and other conventional anticancer drugs may be a future direction for cancer treatment.

Abstract

Reprogramming of glucose metabolism provides sufficient energy and raw materials for the proliferation, metastasis, and immune escape of cancer cells, which is enabled by glucose metabolism-related enzymes that are abundantly expressed in a broad range of cancers. Therefore, targeting glucose metabolism enzymes has emerged as a promising strategy for anticancer drug development. Although several glucose metabolism modulators have been approved for cancer treatment in recent years, some limitations exist, such as a short half-life, poor solubility, and numerous adverse effects. With the rapid development of medicinal chemicals, more advanced and effective glucose metabolism enzyme-targeted anticancer drugs have been developed. Additionally, several studies have found that some natural products can suppress cancer progression by regulating glucose metabolism enzymes. In this review, we summarize the mechanisms underlying the reprogramming of glucose metabolism and present enzymes that could serve as therapeutic targets. In addition, we systematically review the existing drugs targeting glucose metabolism enzymes, including small-molecule modulators and natural products. Finally, the opportunities and challenges for glucose metabolism enzyme-targeted anticancer drugs are also discussed. In conclusion, combining glucose metabolism modulators with conventional anticancer drugs may be a promising cancer treatment strategy.

Evaluation of the 18F-FDG-PET/CT uptake association with pathological and immunohistochemistry features in esophagogastric adenocarcinoma

BACKGROUND

The present study aimed to analyze the association between 18F-fluorodeoxyglucose (FDG) uptake and histologic panel in esophagogastric adenocarcinoma.

METHODS

We retrospectively enrolled 26 patients with histologically confirmed esophageal, gastroesophageal junction and gastric adenocarcinoma that have been submitted to pretreatment FDG-PET/CT. We collected the cancer tissue sample of each patient and performed immunohistochemical analyses of the glucose transport protein 1 (GLUT-1), Ki-67, cysteine aspartate-specific proteinases (Caspase)-3 and hexokinase-1, and evaluated the association of these parameters with FDG uptake. The FDG uptake was measured by tumor standardized uptake value (SUV), metabolic tumor volume (MTV), and Total Lesion Glycolysis (TLG). Besides, we analyzed the association of FDG uptake and tumor location, Lauren's histologic subtype, grade of cellular differentiation and intratumoral inflammatory infiltrate.

RESULTS

We found a positive association between GLUT-1 with SUV and TLG, Caspase-3 and SUV and inflammation grade with SUV.

CONCLUSION

Tumor inflammation infiltrate, GLUT-1 and Caspase-3 correlated with 18F-FDG uptake in PET/CT in esophagogastric adenocarcinoma. These findings may help understand the pathologic PET/CT significance in cancer. Understanding the meaning of the 18F-FDG uptake in the field of tumor histologic and immunohistochemistry features is essential to allow the evolution of PET/CT application in esophageal and gastric carcinomas.

The prognostic value of 18F-FDG PET/CT taken immediately after completion of radiotherapy for lung cancer treated with concurrent chemoradiotherapy: A pilot study

PURPOSE

The prognostic value of F-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) taken immediately after completion of radiotherapy in lung cancer patients is not well known. The purpose of this study is to assess the prognostic value of PET/CT taken immediately after completion of radiotherapy in lung cancer patients.

MATERIALS AND METHODS

Patients with primary lung cancer planned to undergo concurrent chemoradiotherapy were enrolled. Patients underwent PET/CT scans at 3 time points: before radiotherapy, within 24hours of completing radiotherapy (im-PET/CT), and 2-9 months after radiotherapy (post-PET/CT). Maximum standardized uptake value (SUV_max) was obtained. A post-PET/CT-SUV_max cut-off of 2.5 was determined as radiotherapy success.

RESULTS

Nineteen patients were enrolled. im-PET/CT-SUV_max for patients in the high post-PET/CT-SUV_max group was significantly higher than that of the low group (P=0.004). Receiver operator curve analysis indicated that im-PET/CT-SUV_max of 4.35 was an optimal cut-off value to discriminate between the two groups. Multivariable analysis showed that a high im-PET/CT-SUV_max was significantly associated with a high post-PET/CT-SUV_max (P=0.003).

CONCLUSION

PET/CT-SUV_max taken immediately following radiotherapy was associated with that evaluated 2-9 months after radiotherapy.

Targeting Energy Metabolism in Cancer Treatment

Cancer is the second most common cause of death worldwide after cardiovascular diseases. The development of molecular and biochemical techniques has expanded the knowledge of changes occurring in specific metabolic pathways of cancer cells. Increased aerobic glycolysis, the promotion of anaplerotic responses, and especially the dependence of cells on glutamine and fatty acid metabolism have become subjects of study. Despite many cancer treatment strategies, many patients with neoplastic diseases cannot be completely cured due to the development of resistance in cancer cells to currently used therapeutic approaches. It is now becoming a priority to develop new treatment strategies that are highly effective and have few side effects. In this review, we present the current knowledge of the enzymes involved in the different steps of glycolysis, the Krebs cycle, and the pentose phosphate pathway, and possible targeted therapies. The review also focuses on presenting the differences between cancer cells and normal cells in terms of metabolic phenotype. Knowledge of cancer cell metabolism is constantly evolving, and further research is needed to develop new strategies for anti-cancer therapies.

Physiologically intense FDG uptake of distal spinal cord on total-body PET/CT

OBJECTIVE

Physiologically mild-to-moderate FDG uptake of the spinal cord was reported. However, we noticed intense FDG uptake of distal spinal cord in several patients without definite spinal cord lesions on total-body PET/CT. Thus, this study aimed to investigate the frequency, pattern, intensity, and associations of FDG uptake in such cases on total-body PET/CT.

METHODS

The clinical characteristics of age, gender, body mass index (BMI), lower extremity symptom, diabetes, and fasting blood glucose level, and total-body FDG PET/CT metabolic parameters of maximum standard uptake value (SUVmax), SUVmax of lean body mass (SUVlbm), and SUVmax of body surface area (SUVbsa), were retrospectively analyzed in 527 patients without definite spinal cord lesions. Intense FDG uptake was defined as greater than liver glucometabolism on visual analysis, and T5 cord was selected as cord background.

RESULTS

Intense FDG uptake of distal spinal cord was observed in 87 out of 527 patients (16.5%) and involved with 2-3 vertebral segments including T11-T12 in 33 cases (38.0%), T12-L1 in 29 (33.3%), and T11-L1 in 25 (28.7%). No lesions were demonstrated on follow-up physical examinations, MRI or contrast-enhanced CT in these 87 cases with intense FDG accumulation in the distal spinal cord. The median SUVmax, SUVlbm, and SUVbsa of distal spinal cord with intense FDG uptake were 3.8 (2.7-5.5), 2.9 (2.2-4.3), and 1.0 (0.7-1.6), respectively. Significant differences in SUVmax, SUVlbm, and SUVbsa of distal cord and cord background were found between the groups with and without intense FDG uptake (P < 0.05). Moreover, significant differences in ratios of distal spinal cord-to-cord background, to mediastinal blood pool, and to liver were observed between two groups (P < 0.05). Intense FDG uptake of distal cord was associated with age, diabetic status, and blood glucose level.

CONCLUSIONS

Intense FDG uptake of distal spinal cord on total-body PET/CT may be physiological, more common in younger age, patients without diabetes, or lower fasting blood glucose.

PET imaging of VEGFR and integrins in glioma tumor xenografts using 89Zr labelled heterodimeric peptide

Vascular endothelial growth factor receptor (VEGFR) and integrin αv are over-expressed in angiogenesis of variety malignant tumors with key roles in angiogenesis, and have been proven as valuable targets for cancer imaging and treatment. In this study, a heterodimeric peptide targeting VEGFR and integrin was designed, and radiolabeled with zirconium-89 (⁸⁹Zr) for PET imaging of glioma. ⁸⁹Zr-DFO-heterodimeric peptide, a the newly developed probe, was prepared with radiochemical yield of 88.7 ± 2.4%. Targeted binding capability of ⁸⁹Zr-DFO-heterodimeric peptide towards U87MG cells was investigated in murine glioma xenograft models, which shows that the designed probe has good binding ability to both targeting sites. Biodistribution indicated that kidney metabolism is the main pathway and tumor uptake of ⁸⁹Zr-DFO-heterodimeric peptide reached the peak of 0.62 ± 0.10% ID/g . U87MG xenograft could be clearly visualized by microPET/CT imaging through 1 to 3 h post-injection of ⁸⁹Zr-DFO-heterodimeric peptide. Importantly, the tumor radiouptake was significantly reduced after blocking, and the imaging effect of this radioactive compound was more obvious than that of monomeric peptide probes. ⁸⁹Zr-DFO-heterodimeric peptide has been demonstrated to show potential as a new radiopharmaceutical probe towards glioma, and multi-target probes do have advantages in tumor imaging.

Comparison between Two Different Scanners for the Evaluation of the Role of 18F-FDG PET/CT Semiquantitative Parameters and Radiomics Features in the Prediction of Final Diagnosis of Thyroid Incidentalomas

The aim of this study was to compare two different tomographs for the evaluation of the role of semiquantitative PET/CT parameters and radiomics features (RF) in the prediction of thyroid incidentalomas (TIs) at ¹⁸F-FDG imaging. A total of 221 patients with the presence of TIs were retrospectively included. After volumetric segmentation of each TI, semiquantitative parameters and RF were extracted. All of the features were tested for significant differences between the two PET scanners. The performances of all of the features in predicting the nature of TIs were analyzed by testing three classes of final logistic regression predictive models, one for each tomograph and one with both scanners together. Some RF resulted significantly different between the two scanners. PET/CT semiquantitative parameters were not able to predict the final diagnosis of TIs while GLCM-related RF (in particular GLCM entropy_log2 e GLCM entropy_log10) together with some GLRLM-related and GLZLM-related features presented the best predictive performances. In particular, GLCM entropy_log2, GLCM entropy_log10, GLZLM SZHGE, GLRLM HGRE and GLRLM HGZE resulted the RF with best performances. Our study enabled the selection of some RF able to predict the final nature of TIs discovered at ¹⁸F-FDG PET/CT imaging. Classic semiquantitative and volumetric PET/CT parameters did not reveal these abilities. Furthermore, a good overlap in the extraction of RF between the two scanners was underlined.

Cancer as a Metabolic Disorder

Cancer has long been considered a genetic disease characterized by a myriad of mutations that drive cancer progression. Recent accumulating evidence indicates that the dysregulated metabolism in cancer cells is more than a hallmark of cancer but may be the underlying cause of the tumor. Most of the well-characterized oncogenes or tumor suppressor genes function to sustain the altered metabolic state in cancer. Here, we review evidence supporting the altered metabolic state in cancer including key alterations in glucose, glutamine, and fatty acid metabolism. Unlike genetic alterations that do not occur in all cancer types, metabolic alterations are more common among cancer subtypes and across cancers. Recognizing cancer as a metabolic disorder could unravel key diagnostic and treatments markers that can impact approaches used in cancer management.

Glucose metabolic profiles evaluated by PET associated with molecular characteristic landscape of gastric cancer

BACKGROUND

Although FDG-PET is widely used in cancer, its role in gastric cancer (GC) is still controversial due to variable [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) uptake. Here, we sought to develop a genetic signature to predict high FDG-avid GC to plan individualized PET and investigate the molecular landscape of GC and its association with glucose metabolic profiles noninvasively evaluated by [¹⁸F]FDG-PET.

METHODS

Based on a genetic signature, PETscore, representing [¹⁸F]FDG avidity, was developed by imaging data acquired from thirty patient-derived xenografts (PDX). The PETscore was validated by [¹⁸F]FDG-PET data and gene expression data of human GC. The PETscore was associated with genomic and transcriptomic profiles of GC using The Cancer Genome Atlas.

RESULTS

Five genes, PLS1, PYY, HBQ1, SLC6A5, and NAT16, were identified for the predictive model for [¹⁸F]FDG uptake of GC. The PETscore was validated in independent PET data of human GC with qRT-PCR and RNA-sequencing. By applying PETscore on TCGA, a significant association between glucose uptake and tumor mutational burden as well as genomic alterations were identified.

CONCLUSION

Our findings suggest that molecular characteristics are underlying the diverse metabolic profiles of GC. Diverse glucose metabolic profiles may apply to precise diagnostic and therapeutic approaches for GC.

Development and Validation of a Radiomics Model Based on 18F-FDG PET of Primary Gastric Cancer for Predicting Peritoneal Metastasis

Objectives

The aim of this study was to develop a preoperative positron emission tomography (PET)-based radiomics model for predicting peritoneal metastasis (PM) of gastric cancer (GC).

Methods

In this study, a total of 355 patients (109PM+, 246PM-) who underwent preoperative fluorine-18-fludeoxyglucose (¹⁸F-FDG) PET images were retrospectively analyzed. According to a 7:3 ratio, patients were randomly divided into a training set and a validation set. Radiomics features and metabolic parameters data were extracted from PET images. The radiomics features were selected by logistic regression after using maximum relevance and minimum redundancy (mRMR) and the least shrinkage and selection operator (LASSO) method. The radiomics models were based on the rest of these features. The performance of the models was determined by their discrimination, calibration, and clinical usefulness in the training and validation sets.

Results

After dimensionality reduction, 12 radiomics feature parameters were obtained to construct radiomics signatures. According to the results of the multivariate logistic regression analysis, only carbohydrate antigen 125 (CA125), maximum standardized uptake value (SUVmax), and the radiomics signature showed statistically significant differences between patients (P<0.05). A radiomics model was developed based on the logistic analyses with an AUC of 0.86 in the training cohort and 0.87 in the validation cohort. The clinical prediction model based on CA125 and SUVmax was 0.76 in the training set and 0.69 in the validation set. The comprehensive model, which contained a rad-score and the clinical factor (CA125) as well as the metabolic parameter (SUVmax), showed promising performance with an AUC of 0.90 in the training cohort and 0.88 in the validation cohort, respectively. The calibration curve showed the actual rate of the nomogram-predicted probability of peritoneal metastasis. Decision curve analysis (DCA) also demonstrated the good clinical utility of the radiomics nomogram.

Conclusions

The comprehensive model based on the rad-score and other factors (SUVmax, CA125) can provide a novel tool for predicting peritoneal metastasis of gastric cancer patients preoperatively.

The harsh microenvironment in early breast cancer selects for a Warburg phenotype

Glucose is converted to energy through “fermentation” or “oxidation.” Generally, if oxygen is available, cells will oxidize glucose to CO₂ because it is more efficient than fermentation, which produces lactic acid. But Warburg noted that cancers ferment glucose at a “remarkable” rate even if O₂ is available! This “Warburg Effect” is still misunderstood because it doesn’t make sense that a cell would ferment glucose when it could get much more energy by oxidizing it. The current paper goes to the heart of this problem by defining the microenvironmental conditions that exist in early cancers that would select for a Warburg Effect. This is important because such cells are much more aggressive and like to lead to cancers that are lethal.

The harsh microenvironment of ductal carcinoma in situ (DCIS) exerts strong evolutionary selection pressures on cancer cells. We hypothesize that the poor metabolic conditions near the ductal center foment the emergence of a Warburg Effect (WE) phenotype, wherein cells rapidly ferment glucose to lactic acid, even in normoxia. To test this hypothesis, we subjected low-glycolytic breast cancer cells to different microenvironmental selection pressures using combinations of hypoxia, acidosis, low glucose, and starvation for many months and isolated single clones for metabolic and transcriptomic profiling. The two harshest conditions selected for constitutively expressed WE phenotypes. RNA sequencing analysis of WE clones identified the transcription factor KLF4 as potential inducer of the WE phenotype. In stained DCIS samples, KLF4 expression was enriched in the area with the harshest microenvironmental conditions. We simulated in vivo DCIS phenotypic evolution using a mathematical model calibrated from the in vitro results. The WE phenotype emerged in the poor metabolic conditions near the necrotic core. We propose that harsh microenvironments within DCIS select for a WE phenotype through constitutive transcriptional reprogramming, thus conferring a survival advantage and facilitating further growth and invasion.

Investigating 18F-FDG PET/CT Parameters as Prognostic Markers for Differentiated Thyroid Cancer: A Systematic Review

Aims: The aim of this study was to determine whether ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) parameters might be prognostic markers for patients with differentiated thyroid carcinoma (DTC).

Methods: We searched for eligible articles in PubMed, EMBASE (Ovid), Cochrane Library, and ClinicalTrials.gov from inception to February 2021. We included studies addressing the association between ¹⁸F-FDG PET/CT parameters and clinical outcomes among patients with DTC. Quality assessment was performed using the Quality in Prognosis Studies (QUIPS) tool.

Results: A total of 25 studies including 2,954 patients (1,994 females, 67.5%) were included; 2,416 patients (81.8%) had papillary thyroid carcinoma (PTC), and the mean or median follow-up time ranged from 19.1 months to 17.1 years. Thirteen (52.0%) studies were assessed as “unclear” for the domain of study participation. The most common timing of PET/CT scans was after thyroidectomy (in 20 of 25 studies, 80%), especially in patients with an elevated thyroglobulin (Tg) and a negative radioiodine whole-body scan (WBS). The most common PET parameter was FDG uptake. Twelve of 17 (70.6%) and 12 of 12 (100%) studies showed an association between PET/CT parameters and disease progression and survival in patients with DTC, respectively.

Conclusion:¹⁸F-FDG PET/CT parameters alone or combined with other variables can serve as prognostic markers to identify DTC patients with poor outcomes, especially in the setting of an elevated Tg and a negative WBS. Future research is needed to confirm these findings and to examine the prognostic value of PET/CT parameters for DTC patients, considering the heterogeneity in PET/CT parameters, unclear information of patients, and PET/CT-adapted treatment modifications.

Dynamic PET image reconstruction utilizing intrinsic data-driven HYPR4D denoising kernel

PURPOSE

Reconstructed PET images are typically noisy, especially in dynamic imaging where the acquired data are divided into several short temporal frames. High noise in the reconstructed images translates to poor precision/reproducibility of image features. One important role of "denoising" is therefore to improve the precision of image features. However, typical denoising methods achieve noise reduction at the expense of accuracy. In this work, we present a novel four-dimensional (4D) denoised image reconstruction framework, which we validate using 4D simulations, experimental phantom, and clinical patient data, to achieve 4D noise reduction while preserving spatiotemporal patterns/minimizing error introduced by denoising.

METHODS

Our proposed 4D denoising operator/kernel is based on HighlY constrained backPRojection (HYPR), which is applied either after each update of OSEM reconstruction of dynamic 4D PET data or within the recently proposed kernelized reconstruction framework inspired by kernel methods in machine learning. Our HYPR4D kernel makes use of the spatiotemporal high frequency features extracted from a 4D composite, generated within the reconstruction, to preserve the spatiotemporal patterns and constrain the 4D noise increment of the image estimate.

RESULTS

Results from simulations, experimental phantom, and patient data showed that the HYPR4D kernel with our proposed 4D composite outperformed other denoising methods, such as the standard OSEM with spatial filter, OSEM with 4D filter, and HYPR kernel method with the conventional 3D composite in conjunction with recently proposed High Temporal Resolution kernel (HYPRC3D-HTR), in terms of 4D noise reduction while preserving the spatiotemporal patterns or 4D resolution within the 4D image estimate. Consequently, the error in outcome measures obtained from the HYPR4D method was less dependent on the region size, contrast, and uniformity/functional patterns within the target structures compared to the other methods. For outcome measures that depend on spatiotemporal tracer uptake patterns such as the nondisplaceable Binding Potential (BP_ND ), the root mean squared error in regional mean of voxel BP_ND values was reduced from ~8% (OSEM with spatial or 4D filter) to ~3% using HYPRC3D-HTR and was further reduced to ~2% using our proposed HYPR4D method for relatively small target structures (~10 mm in diameter). At the voxel level, HYPR4D produced two to four times lower mean absolute error in BP_ND relative to HYPRC3D-HTR.

CONCLUSION

As compared to conventional methods, our proposed HYPR4D method can produce more robust and accurate image features without requiring any prior information.

Long non-coding RNA-based glycolysis-targeted cancer therapy: feasibility, progression and limitations

Metabolism reprogramming is one of the hallmarks of cancer cells, especially glucose metabolism, to promote their proliferation, metastasis and drug resistance. Cancer cells tend to depend on glycolysis for glucose utilization rather than oxidative phosphorylation, which is called the Warburg effect. Genome instability of oncogenes and tumor-inhibiting factors is the culprits for this anomalous glycolytic fueling, which results in dysregulating metabolism-related enzymes and metabolic signaling pathways. It has been extensively demonstrated that protein-coding genes are involved in this process; therefore, glycolysis-targeted therapy has been widely used in anti-tumor combined therapy via small molecular inhibitors of key enzymes and regulatory molecular. The long non-coding RNA, which is a large class of regulatory RNA with longer than 200 nucleotides, is the novel and significant regulator of various biological processes, including metabolic reprogramming. RNA interference and synthetic antisense oligonucleotide for RNA reduction have developed rapidly these years, which presents potent anti-tumor effects both in vitro and in vivo. However, lncRNA-based glycolysis-targeted cancer therapy, as the highly specific and less toxic approach, is still under the preclinical phase. In this review, we highlight the role of lncRNA in glucose metabolism and dissect the feasibility and limitations of this clinical development, which may provide potential targets for cancer therapy.

Cross-validation study between the HRRT and the PET component of the SIGNA PET/MRI system with focus on neuroimaging

Background

The Siemens high-resolution research tomograph (HRRT - a dedicated brain PET scanner) is to this day one of the highest resolution PET scanners; thus, it can serve as useful benchmark when evaluating performance of newer scanners. Here, we report results from a cross-validation study between the HRRT and the whole-body GE SIGNA PET/MR focusing on brain imaging.

Phantom data were acquired to determine recovery coefficients (RCs), % background variability (%BG), and image voxel noise (%). Cross-validation studies were performed with six healthy volunteers using [¹¹C]DTBZ, [¹¹C]raclopride, and [¹⁸F]FDG. Line profiles, regional time-activity curves, regional non-displaceable binding potentials (BP_ND) for [¹¹C]DTBZ and [¹¹C]raclopride scans, and radioactivity ratios for [¹⁸F]FDG scans were calculated and compared between the HRRT and the SIGNA PET/MR.

Results

Phantom data showed that the PET/MR images reconstructed with an ordered subset expectation maximization (OSEM) algorithm with time-of-flight (TOF) and TOF + point spread function (PSF) + filter revealed similar RCs for the hot spheres compared to those obtained on the HRRT reconstructed with an ordinary Poisson-OSEM algorithm with PSF and PSF + filter. The PET/MR TOF + PSF reconstruction revealed the highest RCs for all hot spheres. Image voxel noise of the PET/MR system was significantly lower. Line profiles revealed excellent spatial agreement between the two systems. BP_ND values revealed variability of less than 10% for the [¹¹C]DTBZ scans and 19% for [¹¹C]raclopride (based on one subject only). Mean [¹⁸F]FDG ratios to pons showed less than 12% differences.

Conclusions

These results demonstrated comparable performances of the two systems in terms of RCs with lower voxel-level noise (%) present in the PET/MR system. Comparison of in vivo human data confirmed the comparability of the two systems. The whole-body GE SIGNA PET/MR system is well suited for high-resolution brain imaging as no significant performance degradation was found compared to that of the reference standard HRRT.

Fucoidan Structure and Its Impact on Glucose Metabolism: Implications for Diabetes and Cancer Therapy

Fucoidans are complex polysaccharides derived from brown seaweeds which consist of considerable proportions of L-fucose and other monosaccharides, and sulphated ester residues. The search for novel and natural bioproduct drugs (due to toxicity issues associated with chemotherapeutics) has led to the extensive study of fucoidan due to reports of it having several bioactive characteristics. Among other fucoidan bioactivities, antidiabetic and anticancer properties have received the most research attention in the past decade. However, the elucidation of the fucoidan structure and its biological activity is still vague. In addition, research has suggested that there is a link between diabetes and cancer; however, limited data exist where dual chemotherapeutic efforts are elucidated. This review provides an overview of glucose metabolism, which is the central process involved in the progression of both diseases. We also highlight potential therapeutic targets and show the relevance of fucoidan and its derivatives as a candidate for both cancer and diabetes therapy.

Evaluation of a model-based attenuation correction method on whole-body 18F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging

The bone cannot be evaluated using magnetic resonance attenuation correction (MRAC) with the Dixon sequence. To solve this issue, the present study aimed to evaluate model-based AC for whole-body 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) positron emission tomography (PET)/magnetic resonance imaging (MRI) by creating bone segmentation. We analyzed and evaluated the data of 31 consecutive patients. The Biograph mMR (Siemens Healthcare) was used for clinical whole-body ¹⁸F-FDG PET/MRI with the conventional MRAC method, and OSIRIX MD software was used to analyze the images. After the examination, the new model-based post-processing MRAC was applied to create μ-maps with bone segmentation, and retrospective PET reconstruction was performed using this μ-map. The bone structures of all patients created using model-based MRAC were visually evaluated. Standard uptake values (SUVs) at 11 anatomical positions in PET images, corrected using the μ-map with and without bone segmentation, were measured and compared. The model-based post-processing MRAC was run for all patients, without errors. Visual evaluation revealed that the model-based post-processing MRAC exhibited poor results for six patients. Furthermore, it exhibited an increasing trend of SUV in the brain compared to the conventional method. Locations other than the brain indicated a similar or decreasing trend. The two methods showed a good linear correlation for all patients. However, patients aged < 20 years exhibited a different trend from those aged ≥ 20 years. We should exercise caution when applying this model-based MRAC for younger patients.

Initial evaluation of (4S)-4-(3-[18F]fluoropropyl)-L-glutamate (FSPG) PET/CT imaging in patients with head and neck cancer, colorectal cancer, or non-Hodgkin lymphoma

Purpose

(4S)-4-(3-[¹⁸F]Fluoropropyl)-l-glutamic acid ([¹⁸F]FSPG) measures system x_C⁻ transporter activity and shows promise for oncologic imaging. We present data on tumor uptake of this radiopharmaceutical in human subjects with head and neck cancer (HNC), colorectal cancer (CRC), and non-Hodgkin lymphoma (NHL).

Methods

A total of 15 subjects with HNC (n = 5), CRC (n = 5), or NHL (n = 5) were recruited (mean age 66.2 years, range 44–87 years). 301.4 ± 28.1 MBq (8.1 ± 0.8 mCi) of [¹⁸F]FSPG was given intravenously to each subject, and 3 PET/CT scans were obtained 0–2 h post-injection. All subjects also had a positive [¹⁸F]FDG PET/CT scan within 1 month prior to the [¹⁸F]FSPG PET scan. Semi-quantitative and visual comparisons of the [¹⁸F]FSPG and [¹⁸F]FDG scans were performed.

Results

[¹⁸F]FSPG showed strong uptake in all but one HNC subject. The lack of surrounding brain uptake facilitated tumor delineation in the HNC patients. [¹⁸F]FSPG also showed tumor uptake in all CRC subjects, but variable uptake in the NHL subjects. While the absolute [¹⁸F]FDG SUV values were comparable or higher than [¹⁸F]FSPG, the tumor-to-background SUV ratios were greater with [¹⁸F]FSPG than [¹⁸F]FDG.

Conclusions

[¹⁸F]FSPG PET/CT showed promising results across 15 subjects with 3 different cancer types. Concordant visualization was mostly observed between [¹⁸F]FSPG and [¹⁸F]FDG PET/CT images, with some inter- and intra-individual uptake variability potentially reflecting differences in tumor biology. The tumor-to-background ratios were greater with [¹⁸F]FSPG than [¹⁸F]FDG in the cancer types evaluated. Future studies based on larger numbers of subjects and those with a wider array of primary and recurrent or metastatic tumors are planned to further evaluate the utility of this novel tracer.

Performance of 18F-fluorodesoxyglucose positron-emission tomography/computed tomography for cancer screening in patients with unprovoked venous thromboembolism: Results from an individual patient data meta-analysis

INTRODUCTION

Venous thromboembolism (VTE) may be the first manifestation of cancer. We aimed at evaluating the performance of ¹⁸F-Fluorodesoxyglucose Positron-Emission Tomography/Computed Tomography (FDG PET/CT) for occult cancer screening in patients with unprovoked VTE.

METHODS

This was a pre-specified analysis of a systematic review and individual patient data meta-analysis including prospective studies assessing cancer screening in patients with unprovoked VTE. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of FDG PET/CT were calculated based on cancer diagnosis during a 1-year follow-up period.

RESULTS

Four studies were identified as using FDG PET/CT as part of their extensive screening strategy. Out of the 332 patients who underwent FDG PET/CT, the scan was interpreted as positive in 67 (20.2%), as equivocal in 27 (8.1%), and as negative in 238 (71.7%). Seventeen (5.1%) patients were diagnosed with cancer at inclusion or during the 12-month follow up period. All cancers were diagnosed at initial screening. Pooled sensitivity, specificity, NPV, and PPV were 87.3% (95% CI, 55.3 to 97.4), 70.2% (95% CI, 48.2 to 85.6), 98.9% (95% CI, 94.3 to 99.7), and 17.9% (95% CI, 8.5 to 33.6), respectively.

CONCLUSION

FDG PET/CT appears to have satisfactory accuracy indices for cancer diagnosis in patients with unprovoked VTE. In particular, it exhibits a very high negative predictive value and could be used to rule out the presence of an underlying occult malignancy in this setting.

Diagnostic imaging in infective endocarditis: a contemporary perspective

INTRODUCTION

Infective endocarditis (IE) remains a diagnostic challenge. Prompt diagnosis is essential for accurate risk stratification and appropriate therapeutic decisions and surgical management. In recent years, the use of multimodal imaging has had a transformative effect on the diagnostic approach of IE in selected patients.

AREAS COVERED

This review assesses published literature on different imaging modalities for the diagnosis of IE published between 1 January 2009 and 1 February 2020. We illustrate the diagnostic approach to IE with three clinical cases.

EXPERT OPINION

Novel approaches to imaging for cardiac and extracardiac complications improve and individualize diagnosis, management, and prognosis in patients with suspected IE. The use of multimodal imaging should be guided by a multidisciplinary group of medical providers that includes infectious disease specialists, radiologists, cardiologists, and cardiothoracic surgeons.

Pretreatment serum neutrophil-to-lymphocyte and monocyte-to-lymphocyte ratios: Two tumor-related systemic inflammatory markers in patients with thymic epithelial tumors

OBJECTIVES

To understand underlying changes in pretreatment serum inflammatory markers associated with thymic epithelial tumors (TETs) development.

METHODS

A retrospective analysis of 113 TETs patients who underwent 18-fluorine fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography combined computed tomography (PET/CT) one to two weeks before tumor resection or biopsy was performed. Pretreatment serum neutrophil, monocyte, platelet, and lymphocyte counts, and fibrinogen and C-reaction protein (CRP) concentrations were measured one day before surgery or biopsy. Neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), and platelet-to-lymphocyte ratio (PLR) were calculated by dividing corresponding cells counts by lymphocyte counts, respectively. The maximum standard uptake value (SUVmax) of ¹⁸F-FDG of primary TETs was applied to reflect tumor glycolytic activity. The student's t-test, one-way ANOVA analysis, Chi-square test, receiver operating characteristic curve analysis, and Logistic regression analysis were used for statistical analysis.

RESULTS

The serum NLR and MLR were significantly higher in TETs patients than in healthy volunteers (P both ≤ 0.001). High serum NLR and MLR were related to the thymic carcinomas (TCs) subtype, elevated Masaoka-Koga (M-K) tumor stage, and metastasis of TETs (P all < 0.005). High serum NLR and MLR were also associated with high SUVmax values of TETs (P all < 0.005), with increasingly differences between groups as the cut-off values defining low-SUVmax and high-SUVmax groups increased. With the medium cutoff of NLR, MLR, and SUVmax of 3.07, 0.25, and 8.00 respectively, the high NLR and MLR levels were significantly associated with high SUVmax level of TETs (P both < 0.005). Moreover, the incidences of co-high SUVmax/NLR and co-high SUVmax/MLR were higher in TETs patients older than 55 years, with TCs, in M-K stage IV, and with metastasis (P all < 0.05). Both the co-high SUVmax/NLR and co-high SUVmax/MLR increased the risk of TETs metastasis (P both < 0.001), while the co-high SUVmax/MLR was also an independent risk factor for TETs metastasis (odds ratio: 3.92, 95% confidence interval: 1.02-15.12, P = 0.047).

CONCLUSION

Pretreatment serum NLR and MLR of TETs patients are two tumor-progression- and tumor-glycolysis-related inflammatory markers. Enhanced tumor glycolytic activity and associated systemic inflammatory reaction may play a synergistic role in TETs metastasis.

HDO production from [2H7]glucose Quantitatively Identifies Warburg Metabolism

Increased glucose uptake and aerobic glycolysis are striking features of many cancers. These features have led to many techniques for screening and diagnosis, but many are expensive, less feasible or have harmful side-effects. Here, we report a sensitive 1H/2H NMR method to measure the kinetics of lactate isotopomer and HDO production using a deuterated tracer. To test this hypothesis, HUH-7 hepatocellular carcinoma and AML12 normal hepatocytes were incubated with [2H7]glucose. 1H/2H NMR data were recorded for cell media as a function of incubation time. The efflux rate of lactate-CH3, lactate-CH2D and lactate-CHD2 was calculated as 0.0033, 0.0071, and 0.0.012 µmol/106cells/min respectively. Differential production of lactate isotopomers was due to deuterium loss during glycolysis. Glucose uptake and HDO production by HUH-7 cells showed a strong correlation, indicating that monitoring the HDO production could be a diagnostic feature in cancers. Deuterium mass balance of [2H7]glucose uptake to 2H-lactate and HDO production is quantitatively matched, suggesting increasing HDO signal could be used to diagnose Warburg (cancer) metabolism. Measuring the kinetics of lactate isotopomer and HDO production by 1H and 2H MR respectively are highly sensitive. Increased T1 of 2H-lactate isotopomers indicates inversion/saturation recovery methods may be a simple means of generating metabolism-based contrast.

Glucose-6-phosphatase Expression-Mediated [18F]FDG Efflux in Murine Inflammation and Cancer Models

PURPOSE

2-Deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) accumulation in inflammatory lesions can confound the diagnosis of cancer. In this study, we investigated [¹⁸F]FDG accumulation and efflux in relation to the genes and proteins involved in glucose metabolism in murine inflammation and cancer models.

PROCEDURES

[¹⁸F]FDG accumulation and [¹⁸F]FDG efflux were measured in cancer cells (breast cancer, glioma, thyroid cancer, and hepatoma cells) and RAW 264.7 cells (macrophages) activated with lipopolysaccharide (LPS). The levels of mRNA expression were measured by real-time quantitative PCR (qPCR). The expression of glucose metabolism-related proteins was detected by western blotting. Dynamic [¹⁸F]FDG positron emission tomography-computed tomography (PET/CT) images were acquired for 2 h in tumor-bearing BALB/c nude mice and inflammatory mice induced by turpentine oil.

RESULTS

[¹⁸F]FDG accumulation in MDA-MB-231 (breast cancer) increased with time, but that of HepG2 (hepatoma) reached a constant level after 120 min. [¹⁸F]FDG efflux in HepG2 was faster than that in MDA-MB-231. HepG2 strongly expressed glucose-6-phosphatase (G6Pase) compared with MDA-MB-231. [¹⁸F]FDG accumulation increased with time, and [¹⁸F]FDG efflux accelerated after the activation of RAW 264.7 cells. The expression levels of G6Pase, glucose transporter1 and glucose transporter3 (GLUT1 and GLUT3), and hexokinase II (HK II) increased after the activation of RAW 264.7 cells. [¹⁸F]FDG efflux in activated macrophages was faster than that in MDA-MB-231 cancer cells. MDA-MB-231 strongly expressed HK II protein compared with the activated RAW 264.7. In murine models, [¹⁸F]FDG accumulation in MDA-MB-231 cancer and inflammatory lesions increased with time, but that in HepG2 tumor increased until 20-30 min (SUVmeans ± SD (tumor/muscle), 3.0 ± 1.3) and then decreased (2.1 ± 0.9 at 110-120 min).

CONCLUSIONS

There was no difference in the pattern of [¹⁸F]FDG accumulation with time in MDA-MB-231 tumors and inflammatory lesions. We found that [¹⁸F]FDG efflux accelerated in activated macrophages reflecting increased G6Pase expression after activation and lower expression of HK II protein than that in MDA-MB-231 cancer cells.

Radiosynthesis, in vitro and preliminary in vivo evaluation of the novel glutamine derived PET tracers [18F]fluorophenylglutamine and [18F]fluorobiphenylglutamine

INTRODUCTION

Glucose has been deemed the driving force of tumor growth for decades. However, research has shown that several tumors metabolically shift towards glutaminolysis. The development of radiolabeled glutamine derivatives could be a useful molecular imaging tool for visualizing these tumors. We elaborated on the glutamine-derived PET tracers by developing two novel probes, namely [¹⁸F]fluorophenylglutamine and [¹⁸F]fluorobiphenylglutamine.

MATERIALS AND METHODS

Both tracers were labelled with fluorine-18 using our recently reported ruthenium-based direct aromatic fluorination method. Their affinity was evaluated with a [³H]glutamine inhibition experiment in a human PC-3 and a rat F98 cell line. The imaging potential of [¹⁸F]fluorophenylglutamine and [¹⁸F]fluorobiphenylglutamine was tested using a mouse PC-3 and a rat F98 tumor model.

RESULTS

The radiosynthesis of both tracers was successful with overall non-decay corrected yields of 18.46 ± 4.18% (n = 10) ([¹⁸F]fluorophenylglutamine) and 8.05 ± 3.25% (n = 5) ([¹⁸F]fluorobiphenylglutamine). In vitro inhibition experiments showed a moderate and low affinity of fluorophenylglutamine and fluorobiphenylglutamine, respectively, towards the human ASCT-2 transporter. Both compounds had a low affinity towards the rat ASCT-2 transporter. These results were endorsed by the in vivo experiments with low uptake of both tracers in the F98 rat xenograft, low uptake of [¹⁸F]FBPG in the mice PC-3 xenograft and a moderate uptake of [¹⁸F]FPG in the PC-3 tumors.

CONCLUSION

We investigated the imaging potential of two novel PET radiotracers [¹⁸F]FPG and [¹⁸F]FBPG. [¹⁸F]FPG is the first example of a glutamine radiotracer derivatized with a phenyl group which enables the exploration of further derivatization of the phenyl group to increase the affinity and imaging qualities. We hypothesize that increasing the affinity of [¹⁸F]FPG by optimizing the substituents of the arene ring can result in a high-quality glutamine-based PET radiotracer. Advances in Knowledge and Implications for patient care: We hereby report novel glutamine-based PET-tracers. These tracers are tagged on the arene group with fluorine-18, hereby preventing in vivo defluorination, which can occur with alkyl labelled tracers (e.g. (2S,4R)4-[¹⁸F]fluoroglutamine). [¹⁸F]FPG shows clear tumor uptake in vivo, has no in vivo defluorination and has a straightforward production. We believe this tracer is a good starting point for the development of a high-quality tracer which is useful for the clinical visualization of the glutamine transport.

Gastric schwannoma with giant ulcer and lymphadenopathy mimicking gastric cancer: a case report

Background

Gastric schwannomas are rare benign tumors originating from the intramuscular plexus of the stomach and account for just 2.6% of gastric mesenchymal tumors. Gastric schwannoma (GS) with a surface ulcer is very rare. Herein, we report a rare case of an ulcer-bearing GS, which in conjunction with multiple enlarged regional lymph nodes, readily mimicked gastric cancer (GC).

Case presentation

A 79-year-old female presented with poor appetite and intermittent vomiting of gastric contents during the past month. Gastroscopy revealed a giant crateriform ulcer within the stomach body (at the angular notch). Its raised and indurated border was fragile and bled easily. GC was thus suspected. Contrast-enhanced computer tomography (CT) revealed a mild enhancement of the corresponding irregularly thickened gastric wall, and an annular zone of mucosal discontinuity. Enlarged regional lymph nodes were also found, making GC with metastases of lymph nodes our primary concern. ¹⁸F-fluorodeoxyglueose position emission tomography (¹⁸F-FDG PET)/CT was then performed for further staging. Obviously increased FDG uptake was shown in the gastric lesion ((maximum standardized uptake value (SUV_max) 14.6), but no FDG uptake was observed in the enlarged regional lymph nodes. Given the strong suspicion of GC, subtotal gastrectomy was performed. GS was revealed by postoperative pathology, with no evidence of metastasis in the 13 resected lymph nodes.

Conclusions

This was a rare case of GS with a giant surface ulcer and multiple enlarged regional lymph nodes. The uptake of ¹⁸F-FDG in the tumor was substantially higher than previously published literature reports. Under these circumstances, it is difficult to be differentiated from GC.

Targeting Glucose Transporters for Breast Cancer Therapy: The Effect of Natural and Synthetic Compounds

Reprogramming of cellular energy metabolism is widely accepted to be a cancer hallmark. The deviant energetic metabolism of cancer cells-known as the Warburg effect-consists in much higher rates of glucose uptake and glycolytic oxidation coupled with the production of lactic acid, even in the presence of oxygen. Consequently, cancer cells have higher glucose needs and thus display a higher sensitivity to glucose deprivation-induced death than normal cells. So, inhibitors of glucose uptake are potential therapeutic targets in cancer. Breast cancer is the most commonly diagnosed cancer and a leading cause of cancer death in women worldwide. Overexpression of facilitative glucose transporters (GLUT), mainly GLUT1, in breast cancer cells is firmly established, and the consequences of GLUT inhibition and/or knockout are under investigation. Herein we review the compounds, both of natural and synthetic origin, found to interfere with uptake of glucose by breast cancer cells, and the consequences of interference with that mechanism on breast cancer cell biology. We will also present data where the interaction with GLUT is exploited in order to increase the efficiency or selectivity of anticancer agents, in breast cancer cells.

Emerging therapeutic approaches for canine sarcomas: Pushing the boundaries beyond the conventional

Sarcomas represent a group of genomically chaotic, highly heterogenous tumours of mesenchymal origin with variable mutational load. Conventional therapy with surgery and radiation therapy is effective for managing small, low-grade sarcomas and remains the standard therapeutic approach. For advanced, high-grade, recurrent, or metastatic sarcomas, systemic chemotherapy provides minimal benefit, therefore, there is a drive to develop novel approaches. The discovery of "Coley's toxins" in the 19th century, and their use to stimulate the immune system supported the application of unconventional therapies for the treatment of sarcomas. While promising, this initial work was abandoned and treatment paradigm and disease course of sarcomas was largely unchanged for several decades. Exciting new therapies are currently changing treatment algorithms for advanced carcinomas and melanomas, and similar approaches are being applied to advance the field of sarcoma research. Recent discoveries in subtype-specific cancer biology and the identification of distinct molecular targets have led to the development of promising targeted strategies with remarkable potential to change the landscape of sarcoma therapy in dogs. The purpose of this review article is to describe the current standard of care and limitations as well as emerging approaches for sarcoma therapy that span many of the most active paradigms in oncologic research, including immunotherapies, checkpoint inhibitors, and drugs capable of cellular metabolic reprogramming.

Copper-64 Labeled PEGylated Exosomes for In Vivo Positron Emission Tomography and Enhanced Tumor Retention

Exosomes have attracted tremendous attention due to their important role in physiology, pathology, and oncology, as well as promising potential in biomedical applications. Although great efforts have been dedicated to investigating their biological properties and applications as natural cancer drug-delivery systems, the systemic biodistribution of exosomes remains underexplored. In addition, exosome-based drug delivery is inevitably hindered by the robust liver clearance, leading to suboptimal tumor retention and therapeutic efficiency. In this study, we report one of the first examples using in vivo positron emission tomography (PET) for noninvasive monitoring of copper-64 (⁶⁴Cu)-radiolabeled polyethylene glycol (PEG)-modified exosomes, achieving excellent imaging quality and quantitative measurement of blood residence and tumor retention. PEGylation not only endowed exosomes with a superior pharmacokinetic profile and great accumulation in the tumor versus traditionally reported native exosomes but also reduced premature hepatic sequestration and clearance of exosomes, findings that promise enhanced therapeutic delivery efficacy and safety in future studies. More importantly, this study provides important guidelines about surface engineering, radiochemistry, and molecular imaging in obtaining accurate and quantitative biodistribution information on exosomes, which may benefit future exploration in the realm of exosomes.

Protein kinase C-iota-mediated glycolysis promotes non-small-cell lung cancer progression

Purpose

To determine whether protein kinase C-iota (PKC-iota) is associated with glucose metabolism in non-small-cell lung cancer (NSCLC) and whether its regulatory effect on metabolic and biological changes observed in NSCLC can be mediated by glucose transporter 1 (GLUT1).

Patients and methods

Forty-five NSCLC patients underwent combined ¹⁸F-fludeoxyglucose (¹⁸F-FDG) positron emission tomography and computed tomography (PET/CT) before surgery, and another eighty-one NSCLC patients were followed-up for 1–91 months after tumor resection. The rate of glucose metabolism in NSCLC was quantified by measuring the maximum standardized uptake value (SUVmax) by ¹⁸F-FDG PET/CT. PKC-iota and GLUT1 in NSCLC were detected by immunostaining. In vitro, PKC-iota was knocked down, whereas GLUT1 was silenced with or without PKC-iota overexpression to identify the role of PKC-iota in glycolysis. Spearman’s rank correlation coefficient was used in the correlation analysis. Kaplan-Meier analysis was used to assess survival duration.

Results

There was a positive relationship between PKC-iota expression and SUVmax in NSCLC (r=0.649, P<0.001). PKC-iota expression also showed a positive relationship with GLUT1 in NSCLC tissues (r=0.686, P<0.001). Patients whose NSCLC tissues highly co-expressed PKC-iota and GLUT1 had worse prognosis compared with patients without high co-expression of PKC-iota and GLUT1. In vitro, PKC-iota silencing significantly decreased the expression of GLUT1 and inhibited glucose uptake and glycolysis; c-Myc silencing restrained PKC-iota-mediated GLUT1 elevation; GLUT1 knockdown remarkably suppressed PKC-iota-mediated glycolysis and cell growth.

Conclusion

In NSCLC, the rate of glucose metabolism was positively correlated with PKC-iota expression. PKC-iota increased glucose accumulation and glycolysis by upregulating c-Myc/GLUT1 signaling and is thus involved in tumor progression.

Role of multi-modality functional imaging in differentiation between benign and malignant thyroid 18F-fluorodeoxyglucose incidentaloma

PURPOSE

To evaluate the diagnostic performance of multi-modality functional imaging in differentiating malignant and benign thyroid ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) incidentaloma.

METHODS

This study included 87 patients with thyroid ¹⁸F-FDG incidentalomas detected by ¹⁸F-FDG- positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) and diagnosed at surgery or biopsy, who received ¹⁸F-FDG-PET/CT, diffusion-weighted MR imaging (DWI) and ultrasound elastography (USE). The metabolic tumor volume (MTV), total lesion glycolysis (TLG), apparent diffusion coefficient (ADC) values and ultrasound elasticity scores of thyroid ¹⁸F-FDG incidentalomas were measured and compared in benign and malignant thyroid incidentalomas. The differences of malignant and benign thyroid incidentalomas were tested by χ² test, Fisher's exact test, t test, or Mann-Whitney U test. The diagnostic performance was evaluated and optimal cut-off values were determined in distinguishing malignant from benign thyroid incidentalomas by receiver operating characteristic curve analysis.

RESULTS

MTV, TLG and USE scores of malignant thyroid incidentalomas were significantly higher than benign; but ADC value was significantly lower. We defined the functional imaging parameters TLG < 2.48, ADC > 1.80 × 10^-3mm²/s, and USE score of 1 as markers of benign thyroid incidentalomas and each scored -1 point; TLG ≥ 2.48, ADC ≤ 1.80 × 10^-3mm²/s, and USE score of 4 as markers of malignancy and each scored 1 point. Combined multi-functional imaging parameters achieved the highest performance (84.6% sensitivity and 97.1% specificity) for distinguish malignant from benign thyroid incidentaloma with AUC 0.957 (95% CI 0.917, 0.997).

CONCLUSIONS

Functional imaging might help to distinguishing malignant from benign thyroid ¹⁸F-FDG incidentalomas, and combined multi-functional imaging parameters could improve it.

A radiopharmaceutical [89Zr]Zr-DFO-nimotuzumab for immunoPET with epidermal growth factor receptor expression in vivo

INTRODUCTION

The potential of the positron-emitting zirconium-89 (⁸⁹Zr) (t_1/2 = 78.4 h) has been recently reported for immune positron emission tomography (immunoPET) radioimmunoconjugates design. In our work, we explored the optimized preparation of [⁸⁹Zr]Zr-DFO-nimotuzumab, and evaluated ⁸⁹Zr-labeled monoclonal antibody (mAb) construct for targeted imaging of epidermal growth factor receptor (EGFR) overexpressed in glioma.

METHODS

To optimize the radiolabeling efficiency of ⁸⁹Zr with DFO-nimotuzumab, multiple immunoconjugates and radiolabeling were performed. Radiolabeling yield, radiochemical purity, stability, and activity assay were investigated to characterize [⁸⁹Zr]Zr-DFO-nimotuzumab for chemical and biological integrity. The in vivo behavior of this tracer was studied in mice bearing subcutaneous U87MG (EGFR-positive) tumors received a 3.5 ± 0.2 MBq/dose using PET/CT imaging. One group mice bearing subcutaneous U87MG (EGFR-positive) tumors received [⁸⁹Zr]Zr-DFO-nimotuzumab (3.5 ± 0.2 MBq, ~3 μg) (nonblocking) for immunoPET; the other group had 30 μg predose (blocking) of cold nimotuzumab 24 h prior to [⁸⁹Zr]Zr-DFO-nimotuzumab.

RESULTS

[⁸⁹Zr]Zr-DFO-nimotuzumab was prepared with high radiochemical yield (>90%), radiochemical purity (>99%), and specific activity (115 ± 0.8 MBq/mg). In vitro validation showed that [⁸⁹Zr]Zr-DFO-nimotuzumab had an initial immunoreactive fraction of 0.99 ± 0.05 and remained active for up to 5 days. A biodistribution study revealed excellent stability of [⁸⁹Zr]Zr-DFO-nimotuzumab in vivo compared with ⁸⁹Zr as a bone seeker. High uptake in the liver and heart and modest penetration in the brain were observed, with no significant accumulation of activity in other organs. ImmunoPET studies also indicated prominent image contrast that remarkably high uptake up to ~20%ID/g for nonblocking and ~2%ID/g for blocking in tumor between 12 and 120 h after administration.

CONCLUSION

These studies developed a radiopharmaceutical [⁸⁹Zr]Zr-DFO-nimotuzumab with optimized synthesis. The potential utility of [⁸⁹Zr]Zr-DFO-nimotuzumab in assessing EGFR status in glioma was demonstrated in this study.

Imaging peritoneal metastasis of gastric cancer with 18F-fluorothymidine positron emission tomography/computed tomography: a proof-of-concept study

OBJECTIVE

Peritoneal metastasis (PM) is the most frequent form of metastasis in gastric cancer (GC). The sensitivity of detecting PM by pre-operative imaging modalities is low. Utility of positron emission tomography (PET) with ¹⁸F-fluodeoxyglucose (FDG) for GC is limited, because diffuse-type tumors are not FDG-avid. ¹⁸F-fluothymidine ([F-18]FLT) is a radiotracer that reflects cellular proliferation and the utility of [F-18]FLT-PET in GC has been reported. In this proof-of-concept study, we explored the ability of [F-18]FLT-PET/CT to detect PM of GC previously identified by other imaging modalities.

METHODS

The key eligibility criteria were as follows; (i) histologically proven gastric adenocarcinoma; (ii) evident PM detected by CT performed within 4 weeks prior to registration; (iii) no prior treatment of PM within 4 weeks before registration. [F-18]FLT-PET/CT was performed at National Cancer Center Hospital, and [F-18]FLT-PET/CT images were evaluated independently by two radiologists. Safety assessments were carried out before and after [F-18]FLT-PET/CT. The primary end point was the detection sensitivity of PM.

RESULTS

A total of 19 eligible patients were analyzed, of which 15 (78.9%) had diffuse-type histology. Detection sensitivity of PM, primary lesion, and lymph node metastasis were 73.7% [maximum standardized uptake value (SUVmax): 1.697-13.21], 100% (SUVmax: 2.71-22.01), and 72.7% (SUVmax: 2.079-12.61), respectively. No patients experienced adverse events during or after [F-18]FLT-PET/CT.

CONCLUSION

This proof-of-concept study shows that [F-18]FLT-PET/CT is a sensitive method for detecting PM in GC, and paves the way for future studies investigating the clinical utility of this approach for the detection of clinically non-evident PM in GC. Advances in knowledge: This proof-of-concept study found that [F-18]FLT-PET/CT is a sensitive method for detecting peritoneal metastases in GC.

Atypical 18F-FDG PET-CT uptake in the head and neck; a case-based pictorial review

Positron emission tomography - computed tomography (PET-CT) with fluorine-18-fluorodeoxy-d-glucose (¹⁸F-FDG) has an increasing role in head and neck imaging. Interpretation of ¹⁸F-FDG-tracer uptake in the head and neck requires an understanding of normal physiological patterns of tracer uptake, as well as knowledge of potential pitfalls and atypical patterns. This article presents a select series of unusual patterns of ¹⁸F-FDG uptake on PET-CT imaging of the head and neck.

Feasibility of Systematic Respiratory-Gated Acquisition in Unselected Patients Referred for 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography

Objective

Respiratory motion in ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) induces blurred images, leading to errors in location and quantification for lung and abdominal lesions. Various methods have been developed to correct for these artifacts, and most of current PET/CT scanners are equipped with a respiratory gating system. However, they are not routinely performed because their use is time-consuming. The aim of this study is to assess the feasibility and quantitative impact of a systematic respiratory-gated acquisition in unselected patients referred for FDG PET/CT, without increasing acquisition time.

Methods

Patients referred for a FDG PET/CT examination to the nuclear medicine department of Brest University Hospital were consecutively enrolled, during a 3-month period. Cases presenting lung or liver uptakes were analyzed. Two sets of images were reconstructed from data recorded during a unique acquisition with a continuous table speed of 1 mm/s of the used Biograph mCT Flow PET/CT scanner: standard free-breathing images, and respiratory-gated images. Lesion location and quantitative parameters were recorded and compared.

Results

From October 1 2015 to December 31 2015, 847 patients were referred for FDG PET/CT, 741 underwent a respiratory-gated acquisition. Out of them, 213 (29%) had one or more lung or liver uptake but 82 (38%) had no usable respiratory-gated signal. Accordingly, 131 (62%) patients with 183 lung or liver uptakes were analyzed. Considering the 183 lesions, 140 and 43 were located in the lungs and the liver, respectively. The median (IQR) difference between respiratory-gated images and non-gated images was 18% (4−32) for SUVmax, increasing to 30% (14−57) in lower lobes for lung lesions, and −18% (−40 to −4) for MTV (p < 0.05). Technologists’ active personal dosimetry and mean total examinations duration were not statistically different between periods with and without respiratory gating.

Conclusion

This study showed that a systematic respiratory-gated acquisition without increasing acquisition time is feasible in a daily routine and results in a significant impact on PET quantification. However, clinical impact on patient management remains to be determined.

Glucose deprivation elicits phenotypic plasticity via ZEB1-mediated expression of NNMT

Glucose is considered the primary energy source for all cells, and some cancers are addicted to glucose. Here, we investigated the functional consequences of chronic glucose deprivation in serous ovarian cancer cells. We found that cells resistant to glucose starvation (glucose-restricted cells) demonstrated increased metabolic plasticity that was dependent on NNMT (Nicotinamide N-methyltransferase) expression. We further show that ZEB1 induced NNMT, rendered cells resistant to glucose deprivation and recapitulated metabolic adaptations and mesenchymal gene expression observed in glucose-restricted cells. NNMT depletion reversed metabolic plasticity in glucose-restricted cells and prevented de novo formation of glucose-restricted colonies. In addition to its role in glucose independence, we found that NNMT was required for other ZEB1-induced phenotypes, such as increased migration. NNMT protein levels were also elevated in metastatic and recurrent tumors compared to matched primary carcinomas, while normal ovary and fallopian tube tissue had no detectable NNMT expression. Our studies define a novel ZEB1/NNMT signaling axis, which elicits mesenchymal gene expression, as well as phenotypic and metabolic plasticity in ovarian cancer cells upon chronic glucose starvation. Understanding the causes of cancer cell plasticity is crucial for the development of therapeutic strategies to counter intratumoral heterogeneity, acquired drug resistance and recurrence in high-grade serous ovarian cancer (HGSC).

Diagnostic Value of Volume-Based Fluorine-18-Fluorodeoxyglucose PET/CT Parameters for Characterizing Thyroid Incidentaloma

Objective

To assess clinical value of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) for differentiation of malignant from benign focal thyroid incidentaloma.

Materials and Methods

This retrospective study included 99 patients with focal thyroid incidentaloma of 5216 non-thyroid cancer patients that had undergone PET/CT. PET/CT semi-quantitative parameters, volume-based functional parameters, metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of thyroid incidentaloma were assessed. Receiver-operating characteristic (ROC) analysis was conducted and areas under the curve (AUC) were compared by Hanley and McNeil test to evaluate usefulness of maximum standardized uptake value (SUVmax), MTV and TLG, as markers for differentiating malignant from benign thyroid incidentalomas.

Results

Of 99 thyroid incidentalomas, 64 (64.6%) were malignant and 35 (35.4%) were benign. Malignant thyroid incidentalomas were larger (1.8 cm vs. 1.3 cm, p = 0.006), and had higher SUVmax (11.3 vs. 4.8, p < 0.001), MTV (all p < 0.001) and TLG (all p < 0.001) than benign. TLG 4.0 had the highest performance for differentiation of malignant from benign thyroid incidentaloma in all semi-quantitative parameters with AUC 0.895 by ROC curve analysis. AUC (TLG 4.0) was significantly larger than AUC (SUVmean), AUC (MTV 2.5), AUC (MTV 3.0), AUC (MTV 3.5), AUC (TLG 2.5), and AUC (TLG 3.0), respectively (all, p < 0.05). There was no statistical difference between AUC (TLG 4.0) and AUC (SUVmax) (p > 0.05). A threshold TLG 4.0 of 2.475 had 81.3% sensitivity and 94.3% specificity for identifying malignant thyroid incidentalomas.

Conclusion

Volume-based PET/CT parameters could potentially have clinical value in differential diagnosis of thyroid incidentaloma along with SUVmax.