Value of delayed 18F-FDG-PET imaging in the detection of hepatocellular carcinoma

Incomplete ablation after radiofrequency ablation of hepatocellular carcinoma: analysis of risk factors and prognostic factors

BACKGROUND

Complete ablation rates after a single session of radiofrequency ablation (RFA) of hepatocellular carcinoma (HCC) vary from 48% to 97%. Limited data are available regarding risk factors and prognostic significance of incomplete ablation.

METHODS

Between April 2001 and March 2006, 298 patients underwent RFA of 393 HCC nodules with an intent of complete ablation after a single session. Risk factors for incomplete ablation and its effect on overall survival were analyzed.

RESULTS

Two hundred seventy-three (91.6%) underwent complete tumor ablation, whereas the other 25 (8.4%) underwent incomplete tumor ablation after a single session of RFA. By multivariate analysis, tumor size > 3 cm (P = .049) was found to be the only independent risk factor for incomplete ablation. There was no statistically significant difference in overall survival between patients with complete and incomplete ablation. By univariate analysis, no previous transarterial chemoembolization (TACE), preoperative serum alfa-fetoprotein < or = 100 microg/mL, and complete response after further treatment of incomplete ablation were associated with better overall survival in patients with incomplete ablation.

CONCLUSIONS

This study demonstrated that incomplete ablation after RFA of HCC was associated with tumor size > 3 cm. Our data also suggest that aggressive further treatment of tumors with incomplete ablation aiming at complete tumor response improves overall survival.

Changes in glucose metabolism and gene expression after transfer of anti-angiogenic genes in rat hepatoma

PURPOSE

Human troponin I (TROP), the soluble receptor for vascular endothelial growth factor (sFLT) and angiostatin (ASTAT) are potent inhibitors of endothelial cell proliferation, angiogenesis and tumour growth in vivo. Transfer of these genes into tumours may induce changes not only in perfusion, but also more general ones such as changes in metabolism. The aim of this study was to assess these reactions using FDG-PET and high-throughput methods such as gene profiling.

METHODS

We established Morris hepatoma (MH3924A) cell lines expressing TROP, sFLT or ASTAT and quantified (18)F-fluorodeoxyglucose ((18)FDG) uptake by dynamic positron emission tomography (PET) after tumour inoculation in ACI rats. Furthermore, expression of glucose transporter-1 and -3 (GLUT-1 and GLUT-3) as well as hexokinase-1 and -2 were investigated by RT-PCR and immunohistomorphometry. In addition, gene array analyses were performed.

RESULTS

(18)FDG uptake, vascular fraction and distribution volume were significantly higher in all genetically modified tumours. Immunohistomorphometry showed an increased percentage of hexokinase-1 and -2 as well as GLUT-1 and -3 immunoreactive (ir) cells. Using gene arrays and comparing all three groups of genetically modified tumours, we found upregulated expression of 36 genes related to apoptosis, signal transduction, stress or metabolism.

CONCLUSION

TROP-, sFLT- or ASTAT-expressing MH3924A tumours show enhanced influx of (18)FDG, which seems to be caused by several factors: enhanced exchange of nutrients between blood and tumour, increased amounts of glucose transporters and hexokinases, and increased expression of genes related to apoptosis, matrix and stress, which induce an increased demand for glucose.

Optimization of FDG-PET/CT imaging protocol for evaluation of patients with primary and metastatic liver disease

BACKGROUND

Accurate determination of the extrahepatic extent and intrahepatic distribution of disease is very important in patients with primary and metastatic liver disease for deciding whether a patient receives potentially curable surgery or palliative treatment. Our objective was to evaluate the efficacy of delayed phase FDG-PET/CT imaging in lesion detection and to define its clinical impact compared to triple-phase contrast enhanced CT (CECT).

METHODS

30 patients underwent delayed phase FDG-PET/CT imaging (90 min whole body scan followed by a delayed abdominal scan at 120 min). Maximum standard uptake values (SUVs) and SUV ratios between tumor and normal liver parenchyma (T/N) were evaluated. In addition, comparison was made to CECT obtained within 10 days of the FDG-PET/CT to evaluate for lesion concordance within individual liver segments (Couinaud designation).

RESULTS

Sites of primary malignancies included: colorectal (19), breast (3), pancreas (2), lung (2), carcinoid (2), cholangiocarcinoma (1), and hepatocellular carcinoma (1). There was a significant increase in SUV value of liver lesions between early and delayed acquisition (P < 0.001). Although there was not a significant reduction in liver background activity between the two studies, there was a strong increase in T/N ratio (P < 0.001) allowing better lesion detection by visual inspection. New lesions were identified in 5 of the 30 patients, which were not appreciated on the early scan. Delayed phase FDG-PET/CT identified one lesion which was not present on the corresponding CECT. Delayed phase FDG-PET/CT revealed extrahepatic sites of metastases not appreciated on CECT in 6 patients.

CONCLUSION

Delayed phase FDG-PET/CT protocol improved lesion detectability in primary and metastatic liver disease, revealing new lesions in 17% of the patients. Moreover, FDG-PET/CT identified extrahepatic disease not seen on CECT in 20% of the patients.

Nuclear imaging of neuroendocrine tumours

The diagnosis of neuroendocrine tumours (NETs) and monitoring of therapy in many patients relies mainly on morphological imaging techniques such as computed tomography (CT), ultrasound (US) and magnetic resonance imaging (MRI). However, functional imaging modalities--such as somatostatin receptor scintigraphy (SRS)--have great impact on patient management by providing tools for better staging of the disease, visualization of occult tumour, and evaluation of eligibility for somatostatin analogue treatment. Positron emission tomography (PET) using (18)F-fluoro-deoxy-glucose (FDG) is a powerful functional modality for oncological imaging. Unfortunately, FDG is not accumulated in NETs except in the case of dedifferentiated tumours and tumours with high proliferative activity. Based on the concept of amine precursor uptake and decarboxylation (APUD), the (18)F- and (11)C-labelled amine precursors L-dihydroxyphenylalanine and 5-hydroxy-L-tryptophan (5-HTP) have been utilized for PET imaging of NETs. In comparative studies of patients with a variety of NETs, (11)C5-HTP-PET proved better than CT and SRS by visualizing additional small lesions. With carbidopa premedication orally before (11)C5-HTP-PET examination the tumour uptake could be increased and the urinary radioactivity concentration considerably reduced. This concept may also be applied to (18)F-L-DOPA-PET, a method which in a limited number of studies has gained additional diagnostic information in NET patients compared to SRS and morphological imaging. (68)Ga is available from an in-house generator and has been utilized for labelling of somatostatin analogues for PET imaging of NETs with promising results in a small number of patients. However, SRS is an established functional imaging method for patients with NETs, whereas the role for PET in the clinical routine needs further evaluation in comparative studies in larger groups of patients.

Nuklearmedizinische Diagnostik von Lebertumoren

Standard nuclear medical procedures, such as functional, blood-pool and colloid scintigraphy, play a minor role in the routine workup of liver tumors. However, these techniques are capable of assessing specific organ functions and frequently allow the diagnosis of unclear liver lesions. The sensitivity of scintigraphic procedures can be increased using tomographic imaging (SPECT), the specificity with the introduction of hybrid scanners such as SPECT/CT. Whole body positron emission tomography with 18F-fluoro-deoxy-glucose (FDG) in combination with CT scanning (PET/CT) represents one of the most sensitive imaging modalities for the detection of hepatic metastases and extrahepatic tumor manifestations. For the staging and follow-up of colorectal cancer, FDG-PET/CT represents a standard imaging modality. Metastases from neuroendocrine tumors can be detected using PET and specific tracers such as [68Ga]DOTATOC and [18F]DOPA. Molecular imaging with PET allows the quantification of metabolic processes which can be used for the assessment of an early response to treatment.

Coexistence d’un carcinome hépato-cellulaire et d’une métastase hépatique

We report the case of a cirrhotic patient with a hepatocellular carcinoma and a synchronous hepatic metastasis of a colorectal cancer, both visualized on a positron emission tomography (PET) and a CT scanner. We repeat the need for the arterial phase on CT scanner when a possibility of cirrhosis exists, even in the follow-up of a colorectal cancer. We detail the usual pattern of HCC and the present efficacy of the PET in the diagnosis of HCC.

The role of (18)F-FDG-PET imaging for the selection of liver transplantation candidates among hepatocellular carcinoma patients

Positron emission tomography (PET) using F-18 fluoro-2-deoxy-d-glucose ((18)F-FDG) is now well established as a noninvasive diagnostic tool for the detection of a variety of malignant tumors. However, in the case of hepatocellular carcinoma (HCC), several investigators have reported controversial conclusions and an inadequate sensitivity for PET (50-55%). Nevertheless, a high positive rate of (18)F-FDG accumulation has been reported in patients with high-grade HCC and in those with markedly elevated alpha-fetoprotein (AFP) levels. Here, we retrospectively reviewed 38 HCC cases that received liver transplantation (LT) at our center between November 2000 and July 2004 and underwent whole-body PET imaging. (18)F-FDG uptake was assessed in the liver, and its prognostic significance was investigated. Of 38 patients enrolled, 13 patients had positive PET scans for a liver tumor. When we analyzed the association between tumor factors and PET+ (greater PET lesion uptake) in the liver, preoperative AFP level and vascular invasion were found to be significantly associated with PET+ (P = 0.003 and P < 0.001, respectively). However, the association between histological grade and PET+ findings did not reach statistical significant difference (P = 0.074). Moreover, the 2-year recurrence-free survival rate of PET- patients was significantly higher than that of PET+ patients (85.1% vs. 46.1%) (P = 0.0005). Of 6 PET+ patients who met the Milan criteria, 4 patients (66.7%) had recurrence, but all 20 PET- patients who met the Milan criteria were recurrence free. Thus, PET imaging could be a good preoperative tool for estimating the post-LT risk of tumor recurrence, because histological grade and vascular invasion cannot be determined preoperatively. Importantly, our results indicate that tumor recurrence can be highly anticipated for PET-imaging-positive HCC patients who satisfy the Milan criteria. We advise that PET+ HCC patients be selected cautiously for LT.

Gastrointestinal tract malignancies and positron emission tomography: an overview

(18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) imaging is highly accurate in restaging colorectal cancer, esophageal cancer, and gastrointestinal stromal tumors. Overall, it compares favorably with anatomical imaging in the evaluation of tumor recurrence because metabolic abnormalities usually precede a structural change. Initial staging of these malignancies with PET is best used in patients with locally advanced disease who may benefit from curative resection if distant metastases are not found. It also appears to have great potential in predicting histopathologic response to neoadjuvant therapy and in monitoring the success of radiofrequency ablation and (90)Y microspheres radioembolization soon after intervention. FDG-PET can be used in other gastrointestinal malignancies as a prognostic tool and to detect distant disease but its role has not yet been well defined.

Staging and current treatment of hepatocellular carcinoma

Early-stage hepatocellular carcinoma (HCC) is typically clinically silent, and HCC is often advanced at first manifestation. Without treatment, the 5-year survival rate is less than 5%. The selected treatment depends on the presence of comorbidity; tumor size, location, and morphology; and the presence of metastatic disease. Complete surgical resection followed by hepatic transplantation offers the best long-term survival, but few patients are eligible for this therapy. All other therapies are palliative. Radiofrequency ablation is the preferred method for managing unresectable small HCCs that are few in number. More widespread disease is treated with percutaneous therapies such as chemoembolization and selective internal radiation therapy. Systemic administration of biologic and chemotherapeutic agents is minimally successful in slowing the growth of HCC and typically is used to control symptoms in patients with overwhelming disease. A multidisciplinary approach that includes surgery, systemic therapy, and radiation therapy and that is based on the cooperation of radiation oncologists, interventional and diagnostic radiologists, hepatologists, and pathologists may offer the best chance of a cure or at least a longer and more normal life. To participate effectively in this effort, radiologists must be familiar with staging and treatment options for HCC and with the factors that affect the choice of management method.