The value of [11C]-acetate PET and [18F]-FDG PET in hepatocellular carcinoma before and after treatment with transarterial chemoembolization and bevacizumab

Qualitative and quantitative differentiation efficiency of dual-tracer PET/CT with 18F-fluorodeoxyglucose and 11C-acetate for primary hepatocellular carcinoma: a systematic review and meta-analysis

PURPOSE

Primary hepatocellular carcinoma (HCC) represents a substantial global health challenge. Early diagnosis of HCC is crucial for improved patient outcomes. The aim of this study was to assess qualitative and quantitative diagnostic performance of PET/CT using 11C-acetate and [18F]-fluorodeoxyglucose (FDG) in detection of primary HCC and to determine if 11C-acetate added to [18F]-FDG alleviates the low sensitivity rate mentioned in guidelines.

METHODS

Protocol was pre-registered at https://osf.io/2vcb9 . We searched PubMed, Web of Science, Embase, and the Cochrane Library for included studies. Quality Assessment of Diagnostic Accuracy Studies 2 was used to assess the risk of bias. Possible sources of statistical heterogeneity were explored. Additionally, mentioned three PET/CT tests were evaluated for their diagnostic performance in differentiating HCC from its differential diagnoses. Grades of Recommendation, Assessment, Development, and Evaluation was used to assess quality of generated evidence.

RESULTS

Twenty-four studies were analyzed. Qualitative dual-tracer PET/CT demonstrated 92.0% per-lesion sensitivity, and a significantly higher direct sensitivity difference of 30% to conventional CT, 44.7% to [18F]-FDG, and 12.0% to 11C-acetate. Regarding differentiation rate, [18F]-FDG was superior to 11C-acetate in poorly differentiated lesions while 11C-acetate was superior in well-differentiated lesions. Regarding size, dual tracer combination solved the high missing rate of HCC lesions in 1-2 cm and 2-5 cm groups but could not help in size < 1 cm.

CONCLUSION

Dual-tracer PET/CT utilizing 11C-acetate and [18F]-FDG represents a sensitive method for detecting primary HCC. By concurrently quantifying or qualifying the uptake of 11C-acetate and [18F]-FDG, this multimodal approach enables precise localization of intrahepatic lesions.

Dual-tracer PET/CT in the management of hepatocellular carcinoma

Background & Aims

Combined 18F-fluorodeoxyglucose (FDG) and 11C-acetate (dual-tracer) positron-emission tomography/computed tomography (PET/CT) is being increasingly performed for the management of hepatocellular carcinoma (HCC), although its role is not well defined. Therefore, we evaluated its effectiveness in (i) staging, (ii) characterization of indeterminate lesions on conventional imaging, and (iii) detection of HCC in patients with unexplained elevations in serum alpha-fetoprotein (AFP) levels.

Methods

We retrospectively assessed 525 consecutive patients from three tertiary centers between 2014 and 2020. For staging, we recorded new lesion detection rates, changes in the Barcelona Clinic Liver Cancer (BCLC) classification, and treatment allocation due to dual-tracer PET/CT. To characterize indeterminate lesions and unexplained elevation of serum AFP levels, the sensitivity and specificity of dual-tracer PET/CT in diagnosing HCC were evaluated. A multidisciplinary external review and a cost-benefit analysis of patients for metastatic screening were also performed.

Results

Dual-tracer PET/CT identified new lesions in 14.3% of 273 staging patients, resulting in BCLC upstaging in 11.7% and treatment modifications in 7.7%. It upstaged 8.1% of 260 patients undergoing metastatic screening, with estimated savings of US$495 per patient. It had a sensitivity and specificity of 80.7% (95% CI 71.2-88.6%) and 94.8% (95% CI 90.4-98.6%), respectively, for diagnosing HCC in 201 indeterminate lesions. It detected HCC in 45.1% of 51 patients with unexplained elevations in serum AFP concentrations. External review revealed substantial agreement between local and external image interpretation and patient assessment (n = 273, κ = 0.822; 95% CI 0.803-0.864).

Conclusions

Dual-tracer PET/CT provides added value beyond conventional imaging in patients with HCC by improving staging, confirming HCC diagnosis with high accuracy in patients with indeterminate lesions, and detecting HCC in patients with unexplained elevation of serum AFP.

Impact and implications

Compared to CT or MRI, dual-tracer positron-emission tomography/computed tomography (PET/CT) led to upstaging in 12% of patients with hepatocellular carcinoma (HCC) undergoing staging, resulting in treatment modification in 8% of cases and a cost saving of US$495 per patient. It also accurately detected HCC in high-risk cases where CT or MRI were equivocal or normal. Dual-tracer PET/CT provides added value beyond conventional imaging in patients with HCC by improving staging, confirming HCC diagnosis with high accuracy in patients with indeterminate lesions, and detecting HCC in patients with unexplained elevation of serum AFP.

Preclinical evaluation of 68Ga-radiolabeled trimeric affibody for PDGFRβ-targeting PET imaging of hepatocellular carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) is a highly vascularized solid carcinoma and tumor vessel-targeted molecular imaging might be effective for early diagnosis of HCC. Herein, we developed a novel trimeric affibody (ZTRI) with highly specific binding to the platelet-derived growth factor receptor beta (PDGFRβ). The aim of this study is to evaluate the feasibility of 68Ga-radiolabeled ZTRI ([68Ga]Ga-DOTA-ZTRI) as PET tracer for diagnosis of HCC.

METHODS

The bioinformatics analysis of clinical database and immunoblotting of clinical specimens were performed to validate the potential of PDGFRβ as HCC biomarker. The trimeric affibody ZTRI was conjugated with DOTA-NHS-ester and radiolabeled with 68Ga to produce [68Ga]Ga-DOTA-ZTRI conjugate. Immunoreactivity and specific uptake of [68Ga]Ga-DOTA-ZTRI were assessed by dose-dependent cell binding, autoradiography, and biodistribution analysis. [68Ga]Ga-DOTA-ZTRI PET/CT scanning of diethylnitrosamine (DEN)-induced primary HCC rats and a rare case of idiopathical HCC rhesus monkey was performed to evaluate the imaging capability and radiation dosimetry of [68Ga]Ga-DOTA-ZTRI in vivo.

RESULTS

Excessive PDGFRβ was validated as a representative biomarker of HCC neovascularization. The radiolabeling of [68Ga]Ga-DOTA-ZTRI was achieved at more than 95% radiochemical yield. In vitro assays showed specific uptake of [68Ga]Ga-DOTA-ZTRI in HCC tumor vessels by autoradiography. Animal PET/CT imaging with [68Ga]Ga-DOTA-ZTRI successfully visualized the tumor lesions in primary HCC rats and rhesus monkey, and indicated radiation absorbed dose of 2.03E-02 mSv/MBq for each scanning.

CONCLUSIONS

Our results demonstrated that [68Ga]Ga-DOTA-ZTRI conjugate could be applied as a promising PET tracer for early diagnosis of hepatocellular carcinoma.

Evaluating treatment response following locoregional therapy for hepatocellular carcinoma: A review of the available serological and radiological tools for assessment

Hepatocellular carcinoma (HCC) is an aggressive primary malignancy of the liver and is the third most common cause of cancer-related global mortality. There has been a steady increase in treatment options for HCC in recent years, including innovations in both curative and non-curative therapies. These advances have brought new challenges and necessary improvements in strategies of disease monitoring, to allow early detection of HCC recurrence. Current serological and radiological strategies for post-treatment monitoring and prognostication and their limitations will be discussed and evaluated in this review.

Update on PET Radiopharmaceuticals for Imaging Hepatocellular Carcinoma

Numerous positron emission tomography (PET) targets for detection and staging of hepatocellular cancer have been developed in recent years. Hepatocellular carcinomas (HCCs) are clinically and pathologically heterogeneous tumours with a high tendency to be aggressive and unresponsive to chemotherapy. Early detection is essential, and the need for an adequate imaging biomarker, which can overcome some of the limitations of conventional radiological imaging, is persistent. Flourine-18 (18F) flourodeoxyglucose (FDG), the most widely used PET radiopharmaceutical, has proven disappointing as a possible staple in the evaluation of HCC. This disappointment had led to experimentation with carious radiotracers, such as the choline derivatives, acetate, and prostate-specific membrane antigen, which appear to complement and/or enhance the role of FDG. In this study, we look at the various PET radiopharmaceuticals that have been used for imaging HCC and the particular pathways that they target in HCC and liver cancers.

Clinical big-data-based design of GLUT2-targeted carbon nanodots for accurate diagnosis of hepatocellular carcinoma

Despite advances in diagnostic and therapeutic methods, the prognosis of patients with hepatocellular carcinoma (HCC) remains poor due to the delay in diagnosis. Herein, we aimed to discover a highly sensitive and specific biomarker for HCC based on genomic big data analysis and create an HCC-targeted imaging probe using carbon nanodots (CNDs) as contrast agents. In genomic analysis, we selected glucose transporter 2 (GLUT2) as a potential imaging target for HCC. We confirmed the target suitability by immunohisto-chemistry tests of 339 patient samples, where 81.1% of the patients exhibited underexpression of GLUT2, i.e., higher GLUT2 intensity in non-tumor tissues than in tumor tissues. To visualize GLUT2, we conjugated CNDs with glucosamine (GLN) as a targeting ligand to yield glucosamine-labeled CNDs (GLN-CNDs). A series of in vitro and in vivo experiments were conducted on GLUT2-modified HepG2 cells to confirm the specificity of the GLN-CNDs. Since the GLUT2 expression is higher in hepatocytes than in HCC cells, the GLUT2-targeted contrast agent is highly attached to normal cells. However, it is possible to produce images in the same form as the images obtained with a cancer cell-targeted contrast agent by inverting color scaling. Our results indicate that GLUT2 is a promising target for HCC and that GLN-CNDs may potentially be used as targeted imaging probes for diagnosing HCC.

Dual-tracer positron emission tomography/computed tomography as an imaging probe of de novo lipogenesis in preclinical models of hepatocellular carcinoma

Background

De novo lipogenesis is upregulated in many cancers, and targeting it represents a metabolic approach to cancer treatment. However, the treatment response is unpredictable because lipogenic activity varies greatly among individual tumors, thereby necessitating the assessment of lipogenic activity before treatment. Here, we proposed an imaging probe, positron emission tomography/computed tomography (PET/CT) with dual tracers combining 11C-acetate and 18F-fluorodeoxyglucose (18F-FDG), to assess the lipogenic activity of hepatocellular carcinoma (HCC) and predict the response to lipogenesis-targeted therapy.

Methods

We investigated the association between 11C-acetate/18F-FDG uptake and de novo lipogenesis in three HCC cell lines (from well-differentiated to poorly differentiated: HepG2, Hep3B, and SkHep1) by examining the expression of lipogenic enzymes: acetyl-CoA synthetase 2 (ACSS2), fatty acid synthase (FASN), and ATP citrate lyase (ACLY). The glycolysis level was determined through glycolytic enzymes: pyruvate dehydrogenase expression (PDH). On the basis of the findings of dual-tracer PET/CT, we evaluated the treatment response to a lipase inhibitor (orlistat) in cell culture experiments and xenograft mice.

Results

Dual-tracer PET/CT revealed the lipogenic activity of various HCC cells, which was positively associated with 11C-acetate uptake and negatively associated with 18F-FDG uptake. This finding represents the negative association between 11C-acetate and 18F-FDG uptake. Because these two tracers revealed the lipogenic and glycolytic activity, respectively, which implies an antagonism between lipogenic metabolism and glucose metabolism in HCC. In addition, dual-tracer PET/CT not only revealed the lipogenic activity but also predicted the treatment response to lipogenesis-targeted therapy. For example, HepG2 xenografts with high 11C-acetate but low 18F-FDG uptake exhibited high lipogenic activity and responded well to orlistat treatment, whereas SkHep1 xenografts with low 11C-acetate but high 18F-FDG uptake exhibited lower lipogenic activity and poor response to orlistat.

Conclusion

The proposed non-invasive dual-tracer PET/CT imaging can reveal the lipogenesis and glycolysis status of HCC, thus providing an ideal imaging probe for predicting the therapeutic response of HCC to lipogenesis-targeted therapy.

A Potential Prognostic Marker for Recognizing VEGF-Positive Hepatocellular Carcinoma Based on Magnetic Resonance Radiomics Signature

Objectives

The objective of our project is to explore a noninvasive radiomics model based on magnetic resonance imaging (MRI) that could recognize the expression of vascular endothelial growth factor (VEGF) in hepatocellular carcinoma before operation.

Methods

202 patients with proven single HCC were enlisted and stochastically distributed into a training set (n = 142) and a test set (n = 60). Arterial phase, portal venous phase, balanced phase, delayed phase, and hepatobiliary phase images were used to radiomics features extraction. We retrieved 1906 radiomic features from each phase of every participant’s MRI images. The F-test was applied to choose the crucial features. A logistic regression model was adopted to generate a radiomics signature. By combining independent risk indicators from the fusion radiomics signature and clinico-radiological features, we developed a multivariable logistic regression model that could predict the VEGF status preoperatively through calculating the area under the curve (AUC).

Results

The entire group comprised 108 VEGF-positive individuals and 94 VEGF-negative patients. AUCs of 0.892 (95% confidence interval [CI]: 0.839 - 0.945) in the training dataset and 0.800 (95% CI: 0.682 - 0.918) in the test dataset were achieved by utilizing radiomics features from two phase images (8 features from the portal venous phase and 5 features from the hepatobiliary phase). Furthermore, the nomogram relying on a combined model that included the clinical factors α-fetoprotein (AFP), irregular tumor margin, and the fusion radiomics signature performed well in both the training (AUC = 0.936, 95% CI: 0.898-0.974) and test (AUC = 0.836, 95% CI: 0.728-0.944) datasets.

Conclusions

The combined model acquired from two phase (portal venous and hepatobiliary phase) pictures of gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI could be considered as a credible prognostic marker for the level of VEGF in HCC.

Temporal information guided dynamic dual-tracer PET signal separation network

PURPOSE

The difficulty of dynamic dual-tracer positron emission tomography (PET) technology is to separate the complete single-tracer information from mixed dual-tracer. Traditional methods cannot separate single injection single-scan dynamic dual-tracer PET images. In this paper, we propose a deep learning framework based on gated recurrent unit (GRU) network and evaluate its performance with simulation experiments and realistic monkey data.

METHODS

The proposed single-scan dynamic dual-tracer PET image separation network consists of three parts, including encoder, separation and decoder module. Encoder part is to map the mixed time activity curves (TACs) from the low-dimensional space to the high-dimensional space to get mixed weight vector matrix. Separation part is to capture the temporal information of mixed weight vector matrix using bi-directional GRU (bi-GRU) layer to obtain the single-tracer masks, and the decoding part remaps the high-dimensional single-tracer weight vector matrix to the low-dimensional space to obtain two separated single tracers.

RESULTS

In the simulation experiments under different tracers, phantoms, noise levels, arterial input function (AIF) and k-parameter with Gaussian random, compared to the stacked auto encoder (SAE) network and traditional background subtraction method, GRU-based network has better performance with low bias and mean squared error (MSE). In the realistic study, the image results of GRU network have higher mean structural similarity (MSSIM), and peak signal to noise ratio (PSNR).

CONCLUSIONS

This study demonstrates the feasibility of temporal information guided neural network in single-injection single-scan dynamic dual-tracer PET images separation. The GRU-based network uses TAC temporal information without AIFs to make the separation results more robust and accurate, which significantly outperforms state-of-the-art method qualitatively and quantitatively. This article is protected by copyright. All rights reserved.

Biological Evaluation of [18F]AlF-NOTA-NSC-GLU as a Positron Emission Tomography Tracer for Hepatocellular Carcinoma

Purpose: N-(2-[¹⁸F]fluoropropionyl)-L-glutamate ([¹⁸F]FPGLU) for hepatocellular carcinoma (HCC) imaging has been performed in our previous studies, but its radiosynthesis method and stability in vivo need to be improved. Hence, we evaluated the synthesis and biological properties of a simple [¹⁸F]-labeled glutamate analog, [¹⁸F]AlF-1,4,7-triazacyclononane-1,4,7-triacetic-acid-2-S-(4-isothiocyanatobenzyl)-l-glutamate ([¹⁸F]AlF-NOTA-NSC-GLU), for HCC imaging.

Procedures: [¹⁸F]AlF-NOTA-NSC-GLU was synthesized via a one-step reaction sequence from NOTA-NSC-GLU. In order to investigate the imaging value of [¹⁸F]AlF-NOTA-NSC-GLU in HCC, we conducted positron emission tomography/computed tomography (PET/CT) imaging and competitive binding of [¹⁸F]AlF-NOTA-NSC-GLU in human Hep3B tumor-bearing mice. The transport mechanism of [¹⁸F]AlF-NOTA-NSC-GLU was determined by competitive inhibition and protein incorporation experiments in vitro.

Results: [¹⁸F]AlF-NOTA-NSC-GLU was prepared with an overall radiochemical yield of 29.3 ± 5.6% (n = 10) without decay correction within 20 min. In vitro competitive inhibition experiments demonstrated that the Na⁺-dependent systems XAG-, B0⁺, ASC, and minor XC- were involved in the uptake of [¹⁸F]AlF-NOTA-NSC-GLU, with the Na⁺-dependent system XAG- possibly playing a more dominant role. Protein incorporation studies of the Hep3B human hepatoma cell line showed almost no protein incorporation. Micro-PET/CT imaging with [¹⁸F]AlF-NOTA-NSC-GLU showed good tumor-to-background contrast in Hep3B human hepatoma-bearing mouse models. After [¹⁸F]AlF-NOTA-NSC-GLU injection, the tumor-to-liver uptake ratio of [¹⁸F]AlF-NOTA-NSC-GLU was 2.06 ± 0.17 at 30 min post-injection. In vivo competitive binding experiments showed that the tumor-to-liver uptake ratio decreased with the addition of inhibitors to block the X_AG system.

Conclusions: We have successfully synthesized [¹⁸F]AlF-NOTA-NSC-GLU as a novel PET tracer with good radiochemical yield and high radiochemical purity. Our findings indicate that [¹⁸F]AlF-NOTA-NSC-GLU may be a potential candidate for HCC imaging. Also, a further biological evaluation is underway.

Monitoring Response to Transarterial Chemoembolization in Hepatocellular Carcinoma Using 18F-Fluorothymidine PET

Accurate disease monitoring is essential after transarterial chemoembolization (TACE) in hepatocellular carcinoma (HCC) because of the potential for profound adverse events and large variations in survival outcome. Posttreatment changes on conventional imaging can confound determination of residual or recurrent disease, magnifying the clinical challenge. On the basis of increased expression of thymidylate synthase (TYMS), thymidine kinase 1 (TK-1), and equilibrative nucleoside transporter 1 (SLC29A1) in HCC compared with liver tissue, we conducted a proof-of-concept study evaluating the efficacy of 3'-deoxy-3'-18F-fluorothymidine (18F-FLT) PET to assess response to TACE. Because previous PET studies in HCC have been hampered by high background liver signal, we investigated whether a temporal-intensity voxel clustering (kinetic spatial filtering, or KSF) improved lesion detection. Methods: A tissue microarray was built from 36 HCC samples and from matching surrounding cirrhotic tissue and was stained for TK-1 A prospective study was conducted; 18 patients with a diagnosis of HCC by the criteria of the American Association for the Study of Liver Diseases who were eligible for treatment with TACE were enrolled. The patients underwent baseline conventional imaging and dynamic 18F-FLT PET with KSF followed by TACE. Imaging was repeated 6-8 wk after TACE. The PET parameters were compared with modified enhancement-based RECIST. Results: Cancer Genome Atlas analysis revealed increased RNA expression of TYMS, TK-1, and SLC29A1 in HCC. TK-1 protein expression was significantly higher in HCC (P < 0.05). The sensitivity of 18F-FLT PET for baseline HCC detection was 73% (SUVmax, 9.7 ± 3.0; tumor to liver ratio, 1.2 ± 0.3). Application of KSF did not improve lesion detection. Lesion response after TACE by modified RECIST was 58% (14 patients with 24 lesions). A 30% reduction in mean 18F-FLT PET uptake was observed after TACE, correlating with an observed PET response of 60% (15/25). A significant and profound reduction in the radiotracer delivery parameter K1 after TACE was observed. Conclusion:18F-FLT PET can differentiate HCC from surrounding cirrhotic tissue, with PET parameters correlating with TACE response. KSF did not improve visualization of tumor lesions. These findings warrant further investigation.

Non-FDG PET/CT

The major applications for molecular imaging with PET in clinical practice concern cancer imaging. Undoubtedly, 18F-FDG represents the backbone of nuclear oncology as it remains so far the most widely employed positron emitter compound. The acquired knowledge on cancer features, however, allowed the recognition in the last decades of multiple metabolic or pathogenic pathways within the cancer cells, which stimulated the development of novel radiopharmaceuticals. An endless list of PET tracers, substantially covering all hallmarks of cancer, has entered clinical routine or is being investigated in diagnostic trials. Some of them guard significant clinical applications, whereas others mostly bear a huge potential. This chapter summarizes a selected list of non-FDG PET tracers, described based on their introduction into and impact on clinical practice.

Production of highly polarized [1-13 C]acetate by rapid decarboxylation of [2-13 C]pyruvate - application to hyperpolarized cardiac spectroscopy and imaging

PURPOSE

The objective of the present work was to develop and implement an efficient approach to hyperpolarize [1-¹³ C]acetate and apply it to in vivo cardiac spectroscopy and imaging.

METHODS

Rapid hydrogen peroxide induced decarboxylation was used to convert hyperpolarized [2-¹³ C]pyruvate into highly polarized [1-¹³ C]acetate employing an additional step following rapid dissolution of [2-¹³ C]pyruvate in a home-built multi-sample dissolution dynamic nuclear polarization system. Phantom dissolution experiments were conducted to determine optimal parameters of the decarboxylation reaction, retaining polarization and T₁ of [1-¹³ C]acetate. In vivo feasibility of detecting [1-¹³ C]acetate metabolism is demonstrated using slice-selective spectroscopy and multi-echo imaging of [1-¹³ C]acetate and [1-¹³ C]acetylcarnitine in the healthy rat heart.

RESULTS

The first in vivo signal was observed ~23 s after dissolution. At the corresponding time point in the phantom experiments, 97.9 ± 0.4% of [2-¹³ C]pyruvate were converted into [1-¹³ C]acetate by the decarboxylation reaction. T₁ and polarization of [1-¹³ C]acetate was determined to be 29.7 ± 1.9% and a 47.7 ± 0.5 s. Polarization levels of [2-¹³ C]pyruvate and [1-¹³ C]acetate were not significantly different after transfer to the scanner. In vivo, [1-¹³ C]acetate and [1-¹³ C]acetylcarnitine could be detected using spectroscopy and imaging.

CONCLUSION

Decarboxylation of hyperpolarized [2-¹³ C]pyruvate enables the efficient production of highly polarized [1-¹³ C]acetate that is applicable to study short-chain fatty acid metabolism in the in vivo heart.

Therapeutics for advanced hepatocellular carcinoma: Recent advances, current dilemma, and future directions

Hepatocellular carcinoma (HCC) is one of the most common malignancies and is a serious threat to people's health worldwide. The prognosis of advanced HCC is dim if left untreated. In the clinic, the treatment options for advanced HCC include surgery, radiotherapy, transcatheter arterial chemoembolization, and so forth. In recent years, molecular targeted therapy and immunotherapy have also made great progress, bringing new hope to patients with advanced HCC. In this study, therapeutic advances, current dilemma, and future directions of advanced HCC are reviewed, which might serve as a summary for clinicians and may stimulate future research.