Comparison of (11)C-acetate positron emission tomography and (67)Gallium citrate scintigraphy in patients with hepatocellular carcinoma

PET Imaging and Key Radiotracers for Evaluating Response to Locoregional Therapy in Hepatocellular Carcinoma

Locoregional therapies (LRTs) play a considerable role in the management of hepatocellular carcinoma (HCC), especially for patients who are not suitable for radical resection or transplantation. In clinical practice, assessment of LRTs is mainly based on computed tomography and MR imaging, but functional and metabolic information is less accessible. This article reviews the use of various the standardized uptake value parameters based on PET and multiple radiotracers for managing HCC after treatment with different LRTs, as well as parts of preclinical research. It discusses the current use of PET in more detail, as well as its advantages, disadvantages, and prospects.

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.

Various Aspects of Fasting on the Biodistribution of Radiopharmaceuticals

It is demonstrated that fasting can alter the biodistribution of radiopharmaceuticals in nuclear medicine. Various studies have highlighted that fasting is interpreted to be easy for physicians during PET study, fasting is one of the most important factors determining the usefulness of this protocol. It is well documented that fasting can suppress normal ¹⁸F-FDG PET uptake during nuclear cardiology. However, there is no consensus about the usefulness of fasting on radiopharmaceuticals, especially on ¹⁸F-FDG in PET imaging, but special attention should be paid to the setting of the fasting duration. Nevertheless, it does seem we still need extensive clinical studies in the future. The present study aims to review the various aspects of fasting, especially metabolic alteration on radiopharmaceutical biodistribution. In this study, we focused more on the effect of fasting on ¹⁸F-FDG biodistribution, which alters its imaging contrast in cardiology and cancer imaging. Therefore, shifting substrate metabolism from glucose to free fatty acids during fasting can be an alternative approach to suppress physiological myocardial uptake.

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

Purpose

This prospective study was to investigate the value of [¹¹C]-acetate PET and [¹⁸F]-FDG PET in the evaluation of hepatocellular carcinoma (HCC) before and after treatment with transarterial chemoembolization (TACE) and vascular endothelial growth factor (VEGF) antibody (bevacizumab).

Methods

Twenty-two patients (three women, 19 men; 62 ± 8 years) with HCC verified by histopathology were treated with TACE and bevacizumab (n = 11) or placebo (n = 11). [¹¹C]-acetate PET and [¹⁸F]-FDG PET were performed before and after TACE with bevacizumab or placebo. Comparisons between groups were performed with t-tests and Chi-squared tests, where appropriate. Overall survival (OS) was defined as the time from start of bevacizumab or placebo until the date of death/last follow-up, respectively.

Results

The patient-related sensitivity of [¹¹C]-acetate PET, [¹⁸F]-FDG PET, and combined [¹¹C]-acetate and [¹⁸F]-FDG PET was 68%, 45%, and 73%, respectively. There was a significantly higher rate of conversion from [¹¹C]-acetate positive lesions to negative lesions in patients treated with TACE and bevacizumab as compared with that in patients with TACE and placebo (p < 0.05). In patients with negative acetate PET, the mean OS in patients treated with TACE and bevacizumab was 259 ± 118 days and was markedly shorter as compared with that (668 ± 217 days) in patients treated with TACE and placebo (p < 0.05). In patients treated with TACE and placebo, there was significant difference in mean OS in patients with positive FDG PET as compared with that in patients with negative FDG PET (p < 0.05). The HCC lesions had different tracer avidities showing the heterogeneity of HCC.

Conclusions

Our study suggests that combining [¹⁸F]-FDG with [¹¹C]-acetate PET could be useful for the management of HCC patients and might also provide relevant prognostic and molecular heterogeneity information.

Characterization of hepatic tumors using [11C]metomidate through positron emission tomography: comparison with [11C]acetate

Background

Using positron emission tomography (PET), we compared two tracers, [¹¹C]metomidate ([¹¹C]MTO) and [¹¹C]acetate ([¹¹C]ACE), for the characterization of hepatic tumors.

Methods

Thirty-three patients underwent PET with [¹¹C]MTO and [¹¹C]ACE and magnetic resonance imaging (MRI). Based on the histology of the tumor biopsy, 14 patients had hepatocellular carcinoma (HCC), 9 patients had focal nodular hyperplasia (FNH), and 10 patients had other types of hepatic tumors. Tumor uptake was evaluated by calculating the maximum and mean standardized uptake value and tumor-to-liver ratio.

Results

Altogether, 120 hepatic lesions (59 HCC, 18 FNH, 30 metastases of different primaries, 9 adenomas, and 4 regenerating nodules of liver cirrhosis) were detected by MRI. The overall tumor detection rate was slightly higher for [¹¹C]MTO (39%) than for [¹¹C]ACE (33%). [¹¹C]ACE was more sensitive for HCC detection (50% versus 43%, respectively), whereas [¹¹C]MTO was more sensitive for FNH detection (78% versus 44%, respectively). In HCC patients, the tumor grade correlated with [¹¹C]ACE, but not with [¹¹C]MTO. All of the patients with liver metastases, from various primary tumors (n = 10), were negative for both tracers.

Conclusions

Due to low sensitivity, [¹¹C]MTO and [¹¹C]ACE PET have only limited value in diagnosing hepatic tumors.

The effect of fasting on PET Imaging of Hepatocellular Carcinoma

The clinical utility of positron emission tomography (PET) imaging for liver cancer applications is not clearly defined either for diagnosis or treatment assessment. Previous clinical studies demonstrated that fluorodeoxyglucose (FDG) did not show uptake in some hepatocellular carcinoma (HCC) while acetate showed uptake. Pre-imaging fasting is required for clinical PET imaging with FDG. No studies were done to confirm the effect of fasting on acetate uptake in HCC for PET imaging. We investigated this situation with a woodchuck model of viral infection-induced HCC.

METHODS

Four tumor-bearing and one control woodchucks were involved in this study. They were first imaged by PET in fed state followed by another imaging session one week later when they were fasted over-night. Some animals also had FDG-PET scan that was acquired later on the same day. After imaging studies, animals were sacrificed, and their liver excised for histology. Standardized Uptake Value (SUV) was calculated using a region of interest (ROI) placed on each tumor with focal uptake.

RESULTS

Acetate showed uptake in each HCC lesion when the animals were either fasted or fed with no significant difference in SUV values (p=0.177); some of the tumors were histologically confirmed as well-differentiated HCC while others were confirmed as moderately- or poorly-differentiated HCC; no focal uptake was found in the control animal. For the accompanying FDG scans, the uptake was detected only in animals that were fasted although the uptake pattern was different from that with acetate.

CONCLUSION

This study provided a hint that fasting or not has little impact on PET imaging of HCC with acetate. It also confirmed prior finding regarding tumor heterogeneity that led to different tracer uptake pattern in the same tumor. Human studies are needed to validate the findings from this pre-clinical investigation.

Adding 11C-acetate to 18F-FDG at PET Examination Has an Incremental Value in the Diagnosis of Hepatocellular Carcinoma

OBJECTIVE

The sensitivity of FDG at PET examination of Hepatocellular Carcinoma (HCC) is restricted. In a few studies, all done in Oriental patients, PET-examination with (11)C-acetate has shown a higher accuracy than with FDG. In the current study, the uptake of (11)C-acetate has been compared with the uptake of FDG in the primary HCC in a cohort of Occidental patients.

MATERIAL AND METHODS

44 patients underwent PET-examination with both tracers with a mean of 9 days between the examinations. 26 patients had a microscopical diagnosis and 18 were diagnosed with multimodal radiological methods. At least one relevant radiological examination was available for comparison.

RESULTS

At visual evaluation, 13 of the HCC's were positive at PET-examination using FDG and 34 were positive using (11)C-acetate (p<0.001). Median tumor SUVmean of (11)C-acetate was 4.7 and of FDG was 1.9 (p<0.001). There was also a higher uptake of (11)C-acetate by the surrounding liver tissue than of FDG. Median liver SUVmean of [u]11[/u]C-acetate was 3.2 and of FDG it was 1.7 (p<0.001). This corresponded to a median tumour/liver tissue ratio for (11)C-acetate of 1.4 and for FDG of 1.0 (p<0.05). Previous reports of a negative correlation between the uptake of the tracers were weakly supported. In 4 large tumors some portions being hot using one of the tracers were cold using the other tracer and vice versa.

CONCLUSION

Adding registration with (11)C-acetate to registration with FDG at PET-examination has an incremental value in the diagnosis of HCC. A higher tumor uptake of (11)C-acetate cannot be taken full advantage of because of a higher uptake also by the surrounding liver tissue.

CONFLICT OF INTEREST

None declared.

Functional imaging techniques in hepatocellular carcinoma

Novel biological therapies, including tyrosine kinase inhibitors such as sorafenib, improve the survival of patients with unresectable hepatocellular carcinoma. However, assessment of therapeutic efficacy remains challenging with conventional imaging techniques such as ultrasonography, CT or MRI that predominantly rely on size change to detect a treatment response. A beneficial tumour effect may go unrecognized in some patients who do not show tumour shrinkage and conversely, some patients may be maintained on treatment that is not active. This paper explores the use of functional imaging methods that are showing promise in the assessment of hepatocellular carcinoma.

The potential use of 2-[¹⁸F]fluoro-2-deoxy-D-galactose as a PET/CT tracer for detection of hepatocellular carcinoma

PURPOSE

The aim of the study was to evaluate the feasibility of using the hepatocyte-specific positron emission tomography (PET) tracer 2-[(18)F]fluoro-2-deoxy-D-galactose (FDGal) as a tracer for hepatocellular carcinoma (HCC).

METHODS

In addition to standard clinical investigations, 39 patients with known HCC or suspected of having HCC underwent a partial-body FDGal PET/CT (from base of skull to mid-thigh). Diagnosis of HCC was based on internationally approved criteria. FDGal PET/CT images were analysed for areas with high (hot spots) or low (cold spots) tracer accumulation when compared to surrounding tissue.

RESULTS

Seven patients did not have HCC and FDGal PET/CT was negative in each of them. Twenty-three patients had HCC and were included before treatment. FDGal PET/CT correctly identified 22 of these patients, which was comparable to contrast-enhanced CT. Interestingly, FDGal PET/CT was conclusive in 12 patients in whom conventional imaging techniques were inconclusive and required additional diagnostic investigations or close follow-up. Nine patients were included after treatment of HCC and in these patients FDGal PET/CT was able to distinguish between viable tumour tissue as hot spots and areas with low metabolic activity as cold spots. FDGal PET/CT detected extrahepatic disease in nine patients which was a novel finding in eight patients.

CONCLUSION

FDGal PET/CT has great clinical potential as a PET tracer for detection of extra- but also intrahepatic HCC. In the present study, the specificity of FDGal PET/CT was 100%, which is very promising but needs to be confirmed in a larger, prospective study.

[(Methyl)1-(11)c]-acetate metabolism in hepatocellular carcinoma

PURPOSE

Studies have established the value of [(methyl)1-(11)C]-acetate ([(11)C]Act) combined with 2-deoxy-2[(18)F]fluoro-D-glucose (FDG) for detecting hepatocellular carcinoma (HCC) using positron emission tomography (PET). In this study, the metabolic fate of [(11)C]Act in HCC was characterized.

METHODS

Experiments with acetic acid [1-(14)C] sodium salt ([(14)C]Act) were carried out on WCH-17 cells and freshly derived rat hepatocytes. PET scans with [(11)C]Act were also carried out on woodchucks with HCC before injection of [(14)C]Act. The radioactivity levels in different metabolites were quantified with thin-layer chromatography.

RESULTS

In WCH-17 cells, the predominant metabolite was phosphatidylcholine (PC). Regions of HCCs with the highest [(11)C]Act uptake had higher radioactivity accumulation in lipid-soluble compounds than surrounding hepatic tissues. In those regions, PC and triacylglycerol (TG) accumulated more radioactivity than in surrounding hepatic tissues.

CONCLUSIONS

High [(11)C]Act uptake in HCC is associated with increased de novo lipogenesis. PC and TG are the main metabolites into which the radioactive label from [(11)C]Act is incorporated in HCC.